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Posted to fop-commits@xmlgraphics.apache.org by pb...@apache.org on 2002/12/18 17:25:25 UTC
cvs commit: xml-fop/src/documentation/content/xdocs/design/alt.design alt-properties.xml classes-overview.xml compound-properties.xml coroutines.xml footnotes.xml galleys.xml index.xml keeps.xml properties-classes.xml spaces.xml
pbwest 2002/12/18 08:25:25
Modified: src/documentation/content/xdocs/design/alt.design
alt-properties.xml classes-overview.xml
compound-properties.xml coroutines.xml
footnotes.xml galleys.xml index.xml keeps.xml
properties-classes.xml spaces.xml
Log:
W.I.P. changes to alt.design pages.
Revision Changes Path
1.2 +122 -141 xml-fop/src/documentation/content/xdocs/design/alt.design/alt-properties.xml
Index: alt-properties.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/alt-properties.xml,v
retrieving revision 1.1
retrieving revision 1.2
diff -u -r1.1 -r1.2
--- alt-properties.xml 2 Dec 2002 12:00:11 -0000 1.1
+++ alt-properties.xml 18 Dec 2002 16:25:24 -0000 1.2
@@ -3,170 +3,151 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Implementing Properties</title>
+ <header>
+ <title>Implementing Properties</title>
<authors>
- <person id="pbw" name="Peter B. West" email="pbwest@powerup.com.au"/>
+ <person id="pbw" name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
<title>An alternative properties implementation</title>
<note>
- The following discussion focusses on the relationship between
- Flow Objects in the Flow Object tree, and properties. There
- is no (or only passing) discussion of the relationship between
- properties and traits, and by extension, between properties
- and the Area tree. The discussion is illustrated with some
- pseudo-UML diagrams.
+ The following discussion focusses on the relationship between
+ Flow Objects in the Flow Object tree, and properties. There
+ is no (or only passing) discussion of the relationship between
+ properties and traits, and by extension, between properties
+ and the Area tree.
</note>
<p>
- Property handling is complex and expensive. Varying numbers of
- properties apply to individual Flow Objects
- <strong>(FOs)</strong> in the <strong>FO
- tree </strong> but any property may effectively be
- assigned a value on any element of the tree. If that property
- is inheritable, its defined value will then be available to
- any children of the defining FO.
+ Property handling is complex and expensive. Varying numbers of
+ properties <strong>apply</strong> to individual Flow Objects
+ <strong>(FOs)</strong> in the <strong>FO tree </strong> but
+ any property may effectively be assigned a value on any
+ element of the tree. If that property is inheritable, its
+ defined value will then be available to any children of the
+ defining FO.
</p>
<note>
- <em>(XSL 1.0 Rec)</em> <strong>5.1.4 Inheritance</strong>
- ...The inheritable properties can be placed on any formatting
- object.
+ <em>(XSL 1.0 Rec)</em> <strong>5.1.4 Inheritance</strong>
+ ...The inheritable properties can be placed on any formatting
+ object.
</note>
<p>
- Even if the value is not inheritable, it may be accessed by
- its children through the <code>inherit</code> keyword or the
- <code>from-parent()</code> core function, and potentially by
- any of its descendents through the
- <code>from-nearest-specified-value()</code> core function.
+ Even if the value is not inheritable, it may be accessed by
+ its children through the <code>inherit</code> keyword or the
+ <code>from-parent()</code> core function, and potentially by
+ any of its descendents through the
+ <code>from-nearest-specified-value()</code> core function.
</p>
<p>
- In addition to the assigned values of properties, almost every
- property has an <strong>initial value</strong> which is used
- when no value has been assigned.
+ In addition to the assigned values of properties, almost every
+ property has an <strong>initial value</strong> which is used
+ when no value has been assigned.
</p>
<section>
<title>The history problem</title>
- <p>
- The difficulty and expense of handling properties comes from
- this univeral inheritance possibility. The list of properties
- which are assigned values on any particular <em>FO</em>
- element will not generally be large, but a current value is
- required for each property which applies to the <em>FO</em>
- being processed.
- </p>
- <p>
- The environment from which these values may be selected
- includes, for each <em>FO</em>, for each applicable property,
- the value assigned on this <em>FO</em>, the value which
- applied to the parent of this <em>FO</em>, the nearest value
- specified on an ancestor of this element, and the initial
- value of the property.
- </p>
- </section>
- <section>
- <title>Data requirement and structure</title>
- <p>
- This determines the minimum set of properties and associated
- property value assignments that is necessary for the
- processing of any individual <em>FO</em>. Implicit in this
- set is the set of properties and associated values,
- effective on the current <em>FO</em>, that were assigned on
- that <em>FO</em>.
- </p>
- <p>
- This minimum requirement - the initial value, the
- nearest ancestor specified value, the parent computed value
- and the value assigned to the current element -
- suggests a stack implementation.
- </p>
+ <p>
+ The difficulty and expense of handling properties comes from
+ this univeral inheritance possibility. The list of properties
+ which are assigned values on any particular <em>FO</em>
+ element will not generally be large, but a current value is
+ required for each property which applies to the <em>FO</em>
+ being processed.
+ </p>
+ <p>
+ The environment from which these values may be selected
+ includes, for each <em>FO</em>, <strong>for each applicable
+ property</strong>, the value assigned on this <em>FO</em>,
+ the value which applied to the parent of this <em>FO</em>,
+ the nearest value specified on an ancestor of this element,
+ and the initial value of the property.
+ </p>
</section>
<section>
- <title>Stack considerations</title>
- <p>
- One possibility is to push to the stack only a minimal set
- of required elements. When a value is assigned, the
- relevant form or forms of that value (specified, computed,
- actual) are pushed onto the stack. As long as each
- <em>FO</em> maintains a list of the properties which were
- assigned from it, the value can be popped when the focus of
- FO processing retreats back up the <em>FO</em> tree.
- </p>
- <p>
- The complication is that, for elements which are not
- automatically inherited, when an <em>FO</em> is encountered
- which does <strong>not</strong> assign a value to the
- property, the initial value must either be already at the
- top of the stack or be pushed onto the stack.
- </p>
- <p>
- As a first approach, the simplest procedure may be to push a
- current value onto the stack for every element - initial
- values for non-inherited properties and the parental value
- otherwise. Then perform any processing of assigned values.
- This simplifies program logic at what is hopefully a small
- cost in memory and processing time. It may be tuned in a
- later iteration.
- </p>
- <section>
- <title>Stack implementation</title>
- <p>
- Initial attempts at this implementation have used
- <code>LinkedList</code>s as the stacks, on the assumption
- that
- </p>
- <ul>
- <!-- one of (dl sl ul ol li) -->
- <li>random access would not be required</li>
- <li>
- pushing and popping of list elements requires nearly
- constant (low) time
- </li>
- <li> no penalty for first addition to an empty list</li>
- <li>efficient access to both bottom and top of stack</li>
- </ul>
- <p>
- However, it may be required to perform stack access
- operations from an arbitrary place on the stack, in which
- case it would probably be more efficient to use
- <code>ArrayList</code>s instead.
- </p>
- </section>
+ <title>The Construction Hierarchy</title>
+ <p>
+ Properties are resoved in the <strong>FO tree</strong> in a
+ strictly hierarchical manner. Nodes are detected in the
+ input in a <strong>pre-order</strong> traversal, and are
+ built in the same order. This imples that there are two
+ phases, or states, of property resolution and construction.
+ Any particular FO node is either in a state of constructing
+ its own subtree, or in a stable state where the subtree
+ construction is complete. These states have differenct data
+ requirements.
+ </p>
+ <dl>
+ <dt>Subtree building</dt>
+ <dd>
+ In this state, all properties defined on this node, or any
+ of its ancestors must be available to the subtree. In
+ effect, any property defined on this node must be
+ available to its descendants, as all properties defined on
+ any ancestor are available to this node.
+ </dd>
+ <dt>Stable: subtree building complete</dt>
+ <dd>
+ In this state, only the properties <strong>applicable to
+ this node</strong> need be available.
+ </dd>
+ </dl>
</section>
<section>
- <title>Class vs instance</title>
- <p>
- An individual stack would contain values for a particular
- property, and the context of the stack is the property class
- as a whole. The property instances would be represented by
- the individual values on the stack. If properties are to be
- represented as instantiations of the class, the stack
- entries would presumably be references to, or at least
- referenced from, individual property objects. However, the
- most important information about individual property
- instances is the value assigned, and the relationship of
- this property object to its ancestors and its descendents.
- Other information would include the ownership of a property
- instance by a particular <em>FO</em>, and, in the other
- direction, the membership of the property in the set of
- properties for which an <em>FO</em> has defined values.
- </p>
- <p>
- In the presence of a stack, however, none of this required
- information mandates the instantiation of properties. All
- of the information mentioned so far can be effectively
- represented by a stack position and a link to an
- <em>FO</em>. If the property stack is maintained in
- parallel with a stack of <em>FOs</em>, even that link is
- implicit in the stack position.
- </p>
+ <title>Representing Properties: <property> Classes</title>
+ <section>
+ <title>Class vs instance</title>
+ <p>
+ What information is required of <property> objects?
+ More particularly, what information is particular to the
+ <property> classes, and what to the instantiated
+ objects? The answer to this question depend largely on
+ how the <poroperty> objects are used in the context
+ of layout and Area tree construction. The approach taken
+ in this implementation is that properties are simply flags
+ on certain data values associated with FOs. The semantics
+ of these flags are determined within the layout engine.
+ </p>
+ <p>
+ Certain constant information attaches to individual
+ <property> classes. This information is detailed in
+ the descriptions of individual properties in <em>Section
+ 7</em> of the specification. Such information is
+ represented in <strong>class</strong> fields and data
+ structures within the classes.
+ </p>
+ <p>
+ The "instance" information content of a <property>
+ is:
+ </p>
+ <ul>
+ <li>
+ explicitly, the <strong>PropertyValue</strong> datum of
+ the property, and
+ </li>
+ <li>
+ implicitly, the <strong>Flow Object</strong> to which
+ the property is attached.
+ </li>
+ </ul>
+ <p>
+ Properties, then, serve essentially to link <em>FO
+ instances</em> with <em>PropertyValue instances</em>,
+ attaching certain invariant semantic markers to the
+ PropertyValues in the process. In this implementation,
+ these functions can be realised entirely within the
+ <property> <strong>classes</strong> themselves,
+ without the need to instantiate any objects. In practice,
+ <strong><property> singletons</strong> are
+ instantiated to make access to some invariants simpler.
+ </p>
+ </section>
</section>
<p>
- <strong>Next:</strong> <link href="classes-overview.html"
- >property classes overview.</link>
+ <strong>Next:</strong> <link href="classes-overview.html"
+ >property classes overview.</link>
</p>
</section>
- </body>
+ </body>
</document>
1.5 +175 -188 xml-fop/src/documentation/content/xdocs/design/alt.design/classes-overview.xml
Index: classes-overview.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/classes-overview.xml,v
retrieving revision 1.4
retrieving revision 1.5
diff -u -r1.4 -r1.5
--- classes-overview.xml 9 Dec 2002 08:45:16 -0000 1.4
+++ classes-overview.xml 18 Dec 2002 16:25:24 -0000 1.5
@@ -3,201 +3,188 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Property classes overview</title>
+ <header>
+ <title>Property classes overview</title>
<authors>
<person id="pbw" name="Peter B. West"
- email="pbwest@powerup.com.au"/>
+ email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
- <title>Classes overview</title>
- <section>
- <title>The class of all properties</title>
- <p>
- If individual properties can have a "virtual reality" on the
- stack, where is the stack itself to be instantiated? One
- possibility is to have the stacks as <code>static</code>
- data structures within the individual property classes.
- However, the reduction of individual property instances to
- stack entries allows the possibility of further
- virtualization of property classes. If the individual
- properties can be represented by an integer, i.e. a
- <code>static final int</code>, the set of individual
- property stacks can be collected together into one array.
- Where to put such an overall collection? Creating an
- über-class to accommodate everything that applies to
- property classes as a whole allows this array to be defined
- as a <em><code>static final</code> something[]</em>.
- </p>
- </section>
- <section>
- <title>The overall property classes</title>
- <p>
- This approach has been taken for the experimental code.
- Rather than simply creating a overall class containing
- common elements of properties and acting as a superclass,
- advantage has been taken of the facility for nesting of
- top-level classes. All of the individual property classes
- are nested within the <code>Properties</code> class.
- This has advantages and disadvantages.
- </p>
- <dl>
- <dt>Disadvantages</dt>
- <dd>
- The file becomes extremely cumbersome. This can cause
- problems with "intelligent" editors. E.g.
- <em>XEmacs</em> syntax highlighting virtually grinds to a
- halt with the current version of this file.<br/> <br/>
-
- Possible problems with IDEs. There may be speed problems
- or even overflow problems with various IDEs. The current
- version of this and related files had only been tried with
- the <em>[X]Emacs JDE</em> environment, without difficulties
- apart from the editor speed problems mentioned
- above.<br/> <br/>
-
- Retro look and feel. Not the done Java thing.<br/> <br/>
- </dd>
- <dt>Advantages</dt>
- <dd>
- Everything to do with properties in the one place (more or
- less.)<br/> <br/>
-
- Eliminates the need for a large part of the (sometimes)
- necessary evil of code generation. The One Big File of
- <code>foproperties.xml</code>, with its ancillary xsl, is
- absorbed into the One Bigger File of
- <code>Properties.java</code>. The huge advantage of this
- is that it <strong>is</strong> Java.
- </dd>
- </dl>
- </section>
- <section>
- <title>The property information classes</title>
- <p>
- In fact, in order to keep the size of the file down to more
- a more manageable level, the property information classes of
- static data and methods have been split tentatively into
- three:
- </p>
- <figure src="images/design/alt.design/PropertyStaticsOverview.png" alt="Top level
- property classes"/>
- <dl>
- <dt><link href="PropNames-png.html">PropNames</link></dt>
- <dd>
- Contains an array, <code>propertyNames</code>, of the names of
- all properties, and a set of enumeration constants, one
- for each property name in the <code>PropertyNames</code>
- array. These constants index the name of the properties
- in <code>propertyNames</code>, and must be manually kept in
- sync with the entries in the array. (This was the last of
- the classes split off from the original single class;
- hence the naming tiredness.)
- <br/> <br/>
- </dd>
- <dt><link href="PropertyConsts-png.html">PropertyConsts</link></dt>
- <dd>
- Contains two basic sets of data:<br/>
- Property-indexed arrays and property set
- definitions.<br/> <br/>
-
- <strong>Property-indexed arrays</strong> are elaborations
- of the property indexing idea discussed in relation to the
- arrays of property stacks. One of the arrays is<br/> <br/>
-
- <code>public static final LinkedList[]
- propertyStacks</code><br/> <br/>
-
- This is an array of stacks, implemented as
- <code>LinkedList</code>s, one for each property.<br/> <br/>
-
- The other arrays provide indexed access to fields which
- are, in most cases, common to all of the properties. An
- exception is<br/> <br/>
-
- <code>public static final Method[]
- complexMethods</code><br/> <br/>
-
- which contains a reference to the method
- <code>complex()</code> which is only defined for
- properties which have complex value parsing requirements.
- It is likely that a similar array will be defined for
- properties which allow a value of <em>auto</em>.<br/> <br/>
-
- The property-indexed arrays are initialized by
- <code>static</code> initializers in this class. The
- <code>PropNames</code> class and
- <code>Properties</code>
- nested classes are scanned in order to obtain or derive
- the data necessary for initialization.<br/> <br/>
-
- <strong>Property set definitions</strong> are
- <code>HashSet</code>s of properties (represented by
- integer constants) which belong to each of the categories
- of properties defined. They are used to simplify the
- assignment of property sets to individual FOs.
- Representative <code>HashSet</code>s include
- <em>backgroundProps</em> and
- <em>tableProps</em>.<br/> <br/>
- </dd>
- <dt><link href="Properties-png.html">Properties</link></dt>
- <dd>
- <br/>
- This class contains only sets of constants for use by the
- individual property classes, but it also importantly
- serves as a container for all of the property classes, and
- some convenience pseudo-property classes.<br/> <br/>
-
- <strong>Constants sets</strong> include:<br/> <br/>
-
- <em>Datatype constants</em>. A bitmap set of
- integer constants over a possible range of 2^0 to 2^31
- (represented as -2147483648). E.g.<br/>
- INTEGER = 1<br/>
- ENUM = 524288<br/> <br/>
- Some of the definitions are bit-ORed
- combinations of the basic values. Used to set the
- <em>dataTypes</em> field of the property
- classes.<br/> <br/>
-
- <em>Trait mapping constants</em>. A bitmap set of
- integer constants over a possible range of 2^0 to 2^31
- (represented as -2147483648), representing the manner in
- which a property maps into a <em>trait</em>. Used to set
- the <code>traitMapping</code> field of the property
- classes.<br/> <br/>
-
- <em>Initial value constants</em>. A sequence of
- integer constants representing the datatype of the initial
- value of a property. Used to set the
- <code>initialValueType</code> field of the property
- classes.<br/> <br/>
-
- <em>Inheritance value constants</em>. A sequence
- of integer constants representing the way in which the
- property is normally inherited. Used to set the
- <code>inherited</code> field of the property
- classes.<br/> <br/>
-
- <strong>Nested property classes</strong>. The
- <em>Properties</em> class serves as the holding pen for
- all of the individual property classes, and for property
- pseudo-classes which contain data common to a number of
- actual properties, e.g. <em>ColorCommon</em>.
- </dd>
- </dl>
- </section>
+ <title>Properties: packages</title>
+ <ul>
+ <li>
+ org.apache.fop.fo
+ <dl>
+ <dt><fork href="PropNames.html">PropNames</fork></dt>
+ <dd>
+ This class maintains an array of <fork href=
+ "PropNames.html#propertyNames" >property names</fork>,
+ synchronized to a complete set of property name <fork
+ href= "PropNames.html#NO_PROPERTY" >constants</fork> for
+ indexing property-based arrays. It includes methods to
+ <fork href= "PropNames.html#getPropertyName" >convert an
+ index to a name</fork> and to <fork href=
+ "PropNames.html#getPropertyIndex" >convert a property
+ name to an index</fork>.
+ </dd>
+
+ <dt>
+ <fork href= "PropertyConsts.html" >PropertyConsts</fork>
+ </dt>
+ <dd>
+ A singleton instance of <strong>PropertyConsts</strong>
+ is created by the static initializer of the <fork href=
+ "PropertyConsts.html#pconsts" >pconsts</fork> field.
+ Working from the <property> indices defined in
+ PropNames, the methods in this class collect and supply
+ the values of fields defined in <property> objects
+ into arrays.<br/>
+
+ The heart of this class in the method <fork href=
+ "PropertyConsts.html#setupProperty"
+ >setupProperty</fork>, which constructs the
+ <property> name from the index, instantiates a
+ singleton of the appropriate class, and extracts static
+ fields by reflection from that instance into the arrays
+ of field values.
+ </dd>
+
+ <dt><fork href= "PropertySets.html" >PropertySets</fork></dt>
+ <dd>
+ This class provides a number of
+ <strong>ROBitSet</strong>s representing many of the sets
+ of properties defined in <em>Section 7</em> of the
+ specification. Note that the <em>Border</em>,
+ <em>Padding</em> and <em>Background</em> sets are
+ defined separately.
+ </dd>
+
+ <dt><fork href= "FOPropertySets.html"
+ >FOPropertySets</fork></dt>
+ <dd>
+ This class provides a number of
+ <strong>ROBitSet</strong>s representing sets of
+ properties which are applicable in particular subtrees
+ of the FO tree. These sets are provided so that other
+ properties can be ignored during processing of the
+ subtrees.
+ </dd>
+
+ <dt><fork href= "ShorthandPropSets.html"
+ >ShorthandPropSets</fork></dt>
+ <dd>
+ This class contains arrays of <fork href=
+ "ShorthandPropSets.html#shorthands" >shorthand property
+ indices</fork> and <fork href=
+ "ShorthandPropSets.html#compounds" >compound property
+ indices</fork>, and <strong>ROBitSet</strong>s
+ representing the expansion sets of these shorthands and
+ compounds. Various methods useful in the expansion of
+ these properties are also included.
+ </dd>
+
+ <dt>FOAttributes</dt>
+ <dd></dd>
+ </dl>
+ </li>
+ <li>
+ org.apache.fop.fo.properties
+ <dl>
+ <dt>Property</dt>
+ <dd>
+ The base class for all individual <property> classes.
+ </dd>
+ <dt>ColumnNumber</dt>
+ <dd>
+ The actual <property> class with the lowest index
+ number, followed in the oindex order by properties
+ required for further processing, e.g. FontSize.
+ </dd>
+ <dt>....</dt>
+ <dd>....</dd>
+ <dt>Background</dt>
+ <dd>
+ First in index order of the remainining shorthand
+ properties, followed in index order by all other
+ remaining shorthands.
+ </dd>
+ <dt>....</dt>
+ <dd>....</dd>
+ <dt>AbsolutePosition</dt>
+ <dd>
+ First in index order of the remaining properties.
+ Within this ordering, compound properties precede their
+ expansion properties, and corresponding relative
+ properties precede corresponding absolute properties.
+ </dd>
+ <dt>....</dt>
+ <dd>....</dd>
+ <dt>ZIndex</dt>
+ <dd>
+ The <property> class with the highest index
+ number.
+ </dd>
+ </dl>
+ </li>
+ <li>
+ org.apache.fop.fo.expr
+ <dl>
+ <dt><fork href= "PropertyTokenizer.html"
+ >PropertyTokenizer</fork></dt>
+ <dd>
+ The tokenizer for the <property> expression
+ parser. Defines a set of <fork href=
+ "PropertyTokenizer.html#EOF" >token constants</fork> and
+ returns these with associated token values.
+ </dd>
+
+ <dt><fork href= "PropertyParser.html"
+ >PropertyParser</fork></dt>
+ <dd>
+ This extends <strong>PropertyTokenizer</strong>. It
+ parses <property> expressions on the basis of the
+ tokens passed to it by its superclass, generating
+ <strong>PropertyValue</strong>s, including
+ <strong>PropertyValueList</strong>s.
+ </dd>
+
+ <dt>PropertyException</dt>
+ <dd>
+ The basic class for all <property>-related
+ exceptions. It extends
+ <strong>FOPException</strong>. It is housed in this
+ package by historical accident.
+ </dd>
+
+ <dt>
+ DataTypeNotImplementedException<br/>
+ FunctionNotImplementedException<br/>
+ PropertyNotImplementedException
+ </dt>
+ <dd>
+ A set of particular exceptions extending
+ <strong>PropertyException</strong>. Also in this package
+ by accident.
+ </dd>
+
+ </dl>
+ </li>
+ <li>org.apache.fop.datatypes</li>
+ <li>org.apache.fop.datatypes.indirect</li>
+ </ul>
+ </section>
<p>
- <strong>Previous:</strong> <link href=
- "alt-properties.html" >alt.properties</link>
+ <strong>Previous:</strong> <link href= "alt-properties.html"
+ >alt.properties</link>
</p>
+ <!--
<p>
- <strong>Next:</strong> <link href=
- "properties-classes.html" >Properties classes</link>
+ <strong>Next:</strong> <link href= "properties-classes.html"
+ >Properties classes</link>
</p>
- </section>
- </body>
+ -->
+ </body>
</document>
1.2 +203 -203 xml-fop/src/documentation/content/xdocs/design/alt.design/compound-properties.xml
Index: compound-properties.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/compound-properties.xml,v
retrieving revision 1.1
retrieving revision 1.2
diff -u -r1.1 -r1.2
--- compound-properties.xml 2 Dec 2002 10:19:43 -0000 1.1
+++ compound-properties.xml 18 Dec 2002 16:25:24 -0000 1.2
@@ -3,216 +3,216 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Compound properties</title>
+ <header>
+ <title>Compound properties</title>
<authors>
<person name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
<title>Compound properties in XSLFO</title>
<table>
- <tr>
- <th>Property type</th>
- <th>Section</th>
- <th>Inherited</th>
- <th>'inherit'</th>
- </tr>
- <tr>
- <th><length-range></th>
- </tr>
- <tr>
- <th>minimum</th>
- </tr>
- <tr>
- <th>optimum</th>
- </tr>
- <tr>
- <th>maximum</th>
- </tr>
- <tr>
- <td>block-progression-dimension</td>
- <td>7.14.1</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>inline-progression-dimension</td>
- <td>7.14.5</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>leader-length</td>
- <td>7.21.4</td>
- <td>yes</td>
- <td>yes</td>
- </tr>
- <tr>
- <th><length-conditional></th>
- </tr>
- <tr>
- <th>length</th>
- </tr>
- <tr>
- <th>conditionality</th>
- </tr>
- <tr>
- <td>border-after-width</td>
- <td>7.7.12</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>border-before-width</td>
- <td>7.7.9</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>border-end-width</td>
- <td>7.7.18</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>border-start-width</td>
- <td>7.7.15</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>padding-after</td>
- <td>7.7.32</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>padding-before</td>
- <td>7.7.31</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>padding-end</td>
- <td>7.7.34</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>padding-start</td>
- <td>7.7.33</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <th><length-bp-ip-direction></th>
- </tr>
- <tr>
- <th>block-progression-direction</th>
- </tr>
- <tr>
- <th>inline-progression-direction</th>
- </tr>
- <tr>
- <td>border-separation</td>
- <td>7.26.5</td>
- <td>yes</td>
- <td>yes</td>
- </tr>
- <tr>
- <th><space></th>
- </tr>
- <tr>
- <th>minimum</th>
- </tr>
- <tr>
- <th>optimum</th>
- </tr>
- <tr>
- <th>maximum</th>
- </tr>
- <tr>
- <th>precedence</th>
- </tr>
- <tr>
- <th>conditionality</th>
- </tr>
- <tr>
- <td>letter-spacing</td>
- <td>7.16.2</td>
- <td>yes</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>line-height</td>
- <td>7.15.4</td>
- <td>yes</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>space-after</td>
- <td>7.10.6</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>space-before</td>
- <td>7.10.5</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>space-end</td>
- <td>7.11.1</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>space-start</td>
- <td>7.11.2</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>word-spacing</td>
- <td>7.16.8</td>
- <td>yes</td>
- <td>yes</td>
- </tr>
- <tr>
- <th><keep></th>
- </tr>
- <tr>
- <th>within-line</th>
- </tr>
- <tr>
- <th>within-column</th>
- </tr>
- <tr>
- <th>within-page</th>
- </tr>
- <tr>
- <td>keep-together</td>
- <td>7.19.3</td>
- <td>yes</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>keep-with-next</td>
- <td>7.19.4</td>
- <td>no</td>
- <td>yes</td>
- </tr>
- <tr>
- <td>keep-with-previous</td>
- <td>7.19.5</td>
- <td>no</td>
- <td>yes</td>
- </tr>
+ <tr>
+ <th>Property type</th>
+ <th>Section</th>
+ <th>Inherited</th>
+ <th>'inherit'</th>
+ </tr>
+ <tr>
+ <th><length-range></th>
+ </tr>
+ <tr>
+ <th>minimum</th>
+ </tr>
+ <tr>
+ <th>optimum</th>
+ </tr>
+ <tr>
+ <th>maximum</th>
+ </tr>
+ <tr>
+ <td>block-progression-dimension</td>
+ <td>7.14.1</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>inline-progression-dimension</td>
+ <td>7.14.5</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>leader-length</td>
+ <td>7.21.4</td>
+ <td>yes</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <th><length-conditional></th>
+ </tr>
+ <tr>
+ <th>length</th>
+ </tr>
+ <tr>
+ <th>conditionality</th>
+ </tr>
+ <tr>
+ <td>border-after-width</td>
+ <td>7.7.12</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>border-before-width</td>
+ <td>7.7.9</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>border-end-width</td>
+ <td>7.7.18</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>border-start-width</td>
+ <td>7.7.15</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>padding-after</td>
+ <td>7.7.32</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>padding-before</td>
+ <td>7.7.31</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>padding-end</td>
+ <td>7.7.34</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>padding-start</td>
+ <td>7.7.33</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <th><length-bp-ip-direction></th>
+ </tr>
+ <tr>
+ <th>block-progression-direction</th>
+ </tr>
+ <tr>
+ <th>inline-progression-direction</th>
+ </tr>
+ <tr>
+ <td>border-separation</td>
+ <td>7.26.5</td>
+ <td>yes</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <th><space></th>
+ </tr>
+ <tr>
+ <th>minimum</th>
+ </tr>
+ <tr>
+ <th>optimum</th>
+ </tr>
+ <tr>
+ <th>maximum</th>
+ </tr>
+ <tr>
+ <th>precedence</th>
+ </tr>
+ <tr>
+ <th>conditionality</th>
+ </tr>
+ <tr>
+ <td>letter-spacing</td>
+ <td>7.16.2</td>
+ <td>yes</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>line-height</td>
+ <td>7.15.4</td>
+ <td>yes</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>space-after</td>
+ <td>7.10.6</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>space-before</td>
+ <td>7.10.5</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>space-end</td>
+ <td>7.11.1</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>space-start</td>
+ <td>7.11.2</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>word-spacing</td>
+ <td>7.16.8</td>
+ <td>yes</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <th><keep></th>
+ </tr>
+ <tr>
+ <th>within-line</th>
+ </tr>
+ <tr>
+ <th>within-column</th>
+ </tr>
+ <tr>
+ <th>within-page</th>
+ </tr>
+ <tr>
+ <td>keep-together</td>
+ <td>7.19.3</td>
+ <td>yes</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>keep-with-next</td>
+ <td>7.19.4</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
+ <tr>
+ <td>keep-with-previous</td>
+ <td>7.19.5</td>
+ <td>no</td>
+ <td>yes</td>
+ </tr>
</table>
</section>
- </body>
+ </body>
</document>
1.3 +96 -95 xml-fop/src/documentation/content/xdocs/design/alt.design/coroutines.xml
Index: coroutines.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/coroutines.xml,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- coroutines.xml 2 Dec 2002 12:00:11 -0000 1.2
+++ coroutines.xml 18 Dec 2002 16:25:24 -0000 1.3
@@ -3,116 +3,117 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Implementing co-routines</title>
+ <header>
+ <title>Implementing co-routines</title>
<authors>
<person name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
<title>Implementing Co-routines in FOP</title>
<p>
- All general page layout systems have to solve the same
- fundamental problem: expressing a flow of text with its own
- natural structure as a series of pages corresponding to the
- physical and logical structure of the output medium. This
- simple description disguises many complexities. Version 1.0
- of the Recommendation, in Section 3, <em>Introduction to
- Formatting </em>, includes the following comments.
+ All general page layout systems have to solve the same
+ fundamental problem: expressing a flow of text with its own
+ natural structure as a series of pages corresponding to the
+ physical and logical structure of the output medium. This
+ simple description disguises many complexities. Version 1.0
+ of the Recommendation, in Section 3, <em>Introduction to
+ Formatting </em>, includes the following comments.
</p>
<note>
- [Formatting] comprises several steps, some of which depend on
- others in a non-sequential way.<br/> ...and...<br/>
- [R]efinement is not necessarily a straightforward, sequential
- procedure, but may involve look-ahead, back-tracking, or
- control-splicing with other processes in the formatter.
+ [Formatting] comprises several steps, some of which depend on
+ others in a non-sequential way.<br/> ...and...<br/>
+ [R]efinement is not necessarily a straightforward, sequential
+ procedure, but may involve look-ahead, back-tracking, or
+ control-splicing with other processes in the formatter.
</note>
<p>Section 3.1, <em>Conceptual Procedure</em>, includes:</p>
<note>
- The procedure works by processing formatting objects. Each
- object, while being processed, may initiate processing in
- other objects. While the objects are hierarchically
- structured, the processing is not; processing of a given
- object is rather like a co-routine which may pass control to
- other processes, but pick up again later where it left off.
+ The procedure works by processing formatting objects. Each
+ object, while being processed, may initiate processing in
+ other objects. While the objects are hierarchically
+ structured, the processing is not; processing of a given
+ object is rather like a co-routine which may pass control to
+ other processes, but pick up again later where it left off.
</note>
<section>
<title>Application of co-routines</title>
- <p>
- If one looks only at the flow side of the equation, it's
- difficult to see what the problem might be. The ordering of
- the elements of the flow is preserved in the area tree, and
- where elements are in an hierarchical relationship in the
- flow, they will generally be in an hierarchical relationship
- in the area tree. In such circumstances, the recursive
- processing of the flow seems quite natural.
- </p>
- <p>
- The problem becomes more obvious when one thinks about the
- imposition of an unrelated page structure over the
- hierarchical structure of the document content. Take, e.g.,
- the processing of a nested flow structure which, at a certain
- point, is scanning text and generating line-areas, nested
- within other block areas and possibly other line areas. The
- page fills in the middle of this process. Processing at the
- lowest level in the tree must now suspend, immediately
- following the production of the line-area which filled the
- page. This same event, however, must also trigger the closing
- and flushing to the area tree of every open area of which the last
- line-area was a descendant.
- </p>
- <p>
- Once all of these areas have been closed, some dormant process
- or processes must wake up, flush the area sub-tree
- representing the page, and open a new page sub-tree in the
- area tree. Then the whole nested structure of flow objects
- and area production must be re-activated, at the point in
- processing at which the areas of the previous page were
- finalised, but with the new page environment. The most
- natural way of expressing the temporal relationship of these
- processes is by means of co-routines.
- </p>
- <p>
- Normal sub-routines (methods) display a hierarchical
- relationship where process A suspends on invoking process B,
- which on termination returns control to A which resumes from
- the point of suspension. Co-routines instead have a parallel
- relationship. Process A suspends on invoking process B, but
- process B also suspends on returning control to process A. To
- process B, this return of control appears to be an invocation
- of process A. When process A subsequently invokes B and
- suspends, B behaves as though its previous invocation of A has
- returned, and it resumes from the point of that invocation.
- So control bounces between the two, each one resuming where it
- left off.<br/><br/>
- <strong>Figure 1</strong>
- </p>
- <figure src="images/design/alt.design/coroutines.png" alt="Co-routine diagram"/>
- <p>
- For example, think of a page-production method working on a
- complex page-sequence-master.
- </p>
- <source>
- void makePages(...) {
- ...
- while (pageSequence.hasNext()) {
- ...
- page = generateNextPage(...);
- boolean over = flow.fillPage(page);
- if (over) return;
- }
- }
- </source>
- <p>
- The <code>fillPage()</code> method, when it fills a page, will
- have unfinished business with the flow, which it will want to
- resume at the next call; hence co-routines. One way to
- implement them in Java is by threads synchronised on some
- common argument-passing object.
- </p>
+ <p>
+ If one looks only at the flow side of the equation, it's
+ difficult to see what the problem might be. The ordering of
+ the elements of the flow is preserved in the area tree, and
+ where elements are in an hierarchical relationship in the
+ flow, they will generally be in an hierarchical relationship
+ in the area tree. In such circumstances, the recursive
+ processing of the flow seems quite natural.
+ </p>
+ <p>
+ The problem becomes more obvious when one thinks about the
+ imposition of an unrelated page structure over the
+ hierarchical structure of the document content. Take, e.g.,
+ the processing of a nested flow structure which, at a certain
+ point, is scanning text and generating line-areas, nested
+ within other block areas and possibly other line areas. The
+ page fills in the middle of this process. Processing at the
+ lowest level in the tree must now suspend, immediately
+ following the production of the line-area which filled the
+ page. This same event, however, must also trigger the closing
+ and flushing to the area tree of every open area of which the last
+ line-area was a descendant.
+ </p>
+ <p>
+ Once all of these areas have been closed, some dormant process
+ or processes must wake up, flush the area sub-tree
+ representing the page, and open a new page sub-tree in the
+ area tree. Then the whole nested structure of flow objects
+ and area production must be re-activated, at the point in
+ processing at which the areas of the previous page were
+ finalised, but with the new page environment. The most
+ natural way of expressing the temporal relationship of these
+ processes is by means of co-routines.
+ </p>
+ <p>
+ Normal sub-routines (methods) display a hierarchical
+ relationship where process A suspends on invoking process B,
+ which on termination returns control to A which resumes from
+ the point of suspension. Co-routines instead have a parallel
+ relationship. Process A suspends on invoking process B, but
+ process B also suspends on returning control to process A. To
+ process B, this return of control appears to be an invocation
+ of process A. When process A subsequently invokes B and
+ suspends, B behaves as though its previous invocation of A has
+ returned, and it resumes from the point of that invocation.
+ So control bounces between the two, each one resuming where it
+ left off.<br/><br/>
+ <strong>Figure 1</strong>
+ </p>
+ <figure src="images/design/alt.design/coroutines.png"
+ alt="Co-routine diagram"/>
+ <p>
+ For example, think of a page-production method working on a
+ complex page-sequence-master.
+ </p>
+ <source>
+ void makePages(...) {
+ ...
+ while (pageSequence.hasNext()) {
+ ...
+ page = generateNextPage(...);
+ boolean over = flow.fillPage(page);
+ if (over) return;
+ }
+ }
+ </source>
+ <p>
+ The <code>fillPage()</code> method, when it fills a page, will
+ have unfinished business with the flow, which it will want to
+ resume at the next call; hence co-routines. One way to
+ implement them in Java is by threads synchronised on some
+ common argument-passing object.
+ </p>
</section>
</section>
- </body>
+ </body>
</document>
1.3 +113 -113 xml-fop/src/documentation/content/xdocs/design/alt.design/footnotes.xml
Index: footnotes.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/footnotes.xml,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- footnotes.xml 2 Dec 2002 12:00:11 -0000 1.2
+++ footnotes.xml 18 Dec 2002 16:25:24 -0000 1.3
@@ -3,138 +3,138 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Implementing footnotes</title>
+ <header>
+ <title>Implementing footnotes</title>
<authors>
<person name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
<title>Implementing footnotes in FOP</title>
<p>
- Footnotes present difficulties for page layout primarily
- because their point of invocation in the flow is different
- from their point of appearance in the area tree. All of the
- content lines of a footnote may appear on the same page as its
- invocation point, all may appear on a following page, or the
- lines may be split over a page or pages. (This characteristic
- leads to another problem when a footnote overflows the last
- page of flow content, but that difficulty will not be
- discussed here.) This note considers some aspects of the
- implementation of footnotes in a galley-based design.
+ Footnotes present difficulties for page layout primarily
+ because their point of invocation in the flow is different
+ from their point of appearance in the area tree. All of the
+ content lines of a footnote may appear on the same page as its
+ invocation point, all may appear on a following page, or the
+ lines may be split over a page or pages. (This characteristic
+ leads to another problem when a footnote overflows the last
+ page of flow content, but that difficulty will not be
+ discussed here.) This note considers some aspects of the
+ implementation of footnotes in a galley-based design.
</p>
<section>
<title>Footnotes and galleys</title>
- <p>
- In the structure described in the <link href=
- "galleys.html" >introduction to FOP galleys</link>,
- footnotes would be pre-processed as galleys themselves, but
- they would remain attached as subtrees to their points of
- invocation in the main text. Allocation to a
- footnote-reference-area would only occur in the resolution
- to Area nodes.
- </p>
- <p>
- When footnotes are introduced, the communication between
- galleys and layout manager, as mentioned <link href=
- "galleys.html#pre-processing" >above</link>, would be
- affected. The returned information would two b-p-d values:
- the primary line-area b-p-d impact and the footnote b-p-d
- impact. The distinction is necessary for two reasons; to
- alert the layout manager to the first footnote of the page,
- and because the footnote b-p-d will always impact the
- main-reference-area b-p-d, whereas the primary inline-area
- may not, e.g. in the case of multiple span-areas.
- </p>
+ <p>
+ In the structure described in the <link href= "galleys.html"
+ >introduction to FOP galleys</link>, footnotes would be
+ pre-processed as galleys themselves, but they would remain
+ attached as subtrees to their points of invocation in the
+ main text. Allocation to a footnote-reference-area would
+ only occur in the resolution to Area nodes.
+ </p>
+ <p>
+ When footnotes are introduced, the communication between
+ galleys and layout manager, as mentioned <link href=
+ "galleys.html#pre-processing" >above</link>, would be
+ affected. The returned information would two b-p-d values:
+ the primary line-area b-p-d impact and the footnote b-p-d
+ impact. The distinction is necessary for two reasons; to
+ alert the layout manager to the first footnote of the page,
+ and because the footnote b-p-d will always impact the
+ main-reference-area b-p-d, whereas the primary inline-area
+ may not, e.g. in the case of multiple span-areas.
+ </p>
</section>
<section>
<title>Multiple columns and footnotes</title>
- <note>
- A possible method for multi-column layout and balancing
- with footnotes, using a galley-based approach.
- </note>
- <p>
- This note assumes a galley, as discussed <link href=
- "galleys.html" >elsewhere</link>, flowing text with
- footnotes and possibly other blocks into a possibly
- multi-column area. The logic of flowing into multiple
- columns is trivially applied to a single column. The galley
- is manipulated within the context of the <em>layout
- tree</em>.
- </p>
- <p>
- Associated with the galley are two sets of data.
- One contains the maps of all "natural" break-points and
- the of all hyphenation break-points. This set is
- constructed at the time of construction of the galley and
- is a constant for a given galley. The second contains
- dynamic data which represents one possible attempt to lay
- out the galley. There may be multiple sets of such data
- to reflect varying attempts. The data of this set are,
- essentially, representations of line-areas, with the supporting
- information necessary to determine these line-areas.
- </p>
- <p>
- The line-area data includes the boundaries within the
- galley of each line-area, the boundaries of each column
- and the boundaries of the "page", or main area. When a
- line-area boundary occurs at a hyphenation point, a
- "virtual hyphen" is assumed and accounted for in the
- i-p-d. As mentioned, individual footnote galleys will
- hang from the parent galley. The associated data of the
- footnote galleys is similar: a once-only break-points map,
- and one or more line-area maps. No column boundaries are
- required, but a page boundary is required at the end of
- the last footnote or where a footnote breaks across a page
- boundary.
- </p>
- <p>
- A number of b-p-d values are also maintained. For each
- line-area, the b-p-d, the main area b-p-d increment, the
- footnote b-p-d increment and the footnote's page-related
- b-p-d increment are required. The main-area b-p-d
- increments for any particular line-area are dependent on
- the column position of the line-area. Total b-p-d's are
- also kept: total footnote b-p-d, total main area b-p-d,
- and totals for each column.<br/><br/>
- <strong>Figure 1</strong> Columns before first footnote.
- </p>
- <figure src="images/design/alt.design/initial-column-values.png" alt="Columns before
- first footnote"/>
+ <note>
+ A possible method for multi-column layout and balancing
+ with footnotes, using a galley-based approach.
+ </note>
+ <p>
+ This note assumes a galley, as discussed <link href=
+ "galleys.html" >elsewhere</link>, flowing text with
+ footnotes and possibly other blocks into a possibly
+ multi-column area. The logic of flowing into multiple
+ columns is trivially applied to a single column. The galley
+ is manipulated within the context of the <em>layout
+ tree</em>.
+ </p>
+ <p>
+ Associated with the galley are two sets of data.
+ One contains the maps of all "natural" break-points and
+ the of all hyphenation break-points. This set is
+ constructed at the time of construction of the galley and
+ is a constant for a given galley. The second contains
+ dynamic data which represents one possible attempt to lay
+ out the galley. There may be multiple sets of such data
+ to reflect varying attempts. The data of this set are,
+ essentially, representations of line-areas, with the supporting
+ information necessary to determine these line-areas.
+ </p>
+ <p>
+ The line-area data includes the boundaries within the
+ galley of each line-area, the boundaries of each column
+ and the boundaries of the "page", or main area. When a
+ line-area boundary occurs at a hyphenation point, a
+ "virtual hyphen" is assumed and accounted for in the
+ i-p-d. As mentioned, individual footnote galleys will
+ hang from the parent galley. The associated data of the
+ footnote galleys is similar: a once-only break-points map,
+ and one or more line-area maps. No column boundaries are
+ required, but a page boundary is required at the end of
+ the last footnote or where a footnote breaks across a page
+ boundary.
+ </p>
+ <p>
+ A number of b-p-d values are also maintained. For each
+ line-area, the b-p-d, the main area b-p-d increment, the
+ footnote b-p-d increment and the footnote's page-related
+ b-p-d increment are required. The main-area b-p-d
+ increments for any particular line-area are dependent on
+ the column position of the line-area. Total b-p-d's are
+ also kept: total footnote b-p-d, total main area b-p-d,
+ and totals for each column.<br/><br/>
+ <strong>Figure 1</strong> Columns before first footnote.
+ </p>
+ <figure src=
+ "images/design/alt.design/initial-column-values.png" alt=
+ "Columns before first footnote"/>
</section>
<section>
<title>Balancing columns</title>
- <p>
- <strong>Figure 2</strong> Adding a line area with first
- footnote.
- </p>
- <figure src="images/design/alt.design/line-area-5.png"
- alt="Columns after adding first footnote"/>
- <p>
- Columns are balanced dynamically in the galley preliminary
- layout. While the galley retains its basic linear
- structure, the accompanying data structures accomplish
- column distribution and balancing. As each line-area is
- added, the columns are re-balanced. <strong>N.B.</strong>
- This re-balancing involves only some of the dynamic data
- associated with the participating galley(s). The data
- structures associating breakpoints with the beginning and
- end of individual line areas does not change in
- re-balancing; only the association of line-area with column,
- and, possibly, the various impact values for each line-area.
- <br/><br/>
- <strong>Figure 3</strong> Adding a line area with next
- footnote.
- </p>
- <figure src="images/design/alt.design/line-area-6.png"
- alt="Columns after adding next footnote"/>
+ <p>
+ <strong>Figure 2</strong> Adding a line area with first
+ footnote.
+ </p>
+ <figure src= "images/design/alt.design/line-area-5.png"
+ alt= "Columns after adding first footnote"/>
+ <p>
+ Columns are balanced dynamically in the galley preliminary
+ layout. While the galley retains its basic linear
+ structure, the accompanying data structures accomplish
+ column distribution and balancing. As each line-area is
+ added, the columns are re-balanced. <strong>N.B.</strong>
+ This re-balancing involves only some of the dynamic data
+ associated with the participating galley(s). The data
+ structures associating breakpoints with the beginning and
+ end of individual line areas does not change in
+ re-balancing; only the association of line-area with column,
+ and, possibly, the various impact values for each line-area.
+ <br/><br/>
+ <strong>Figure 3</strong> Adding a line area with next
+ footnote.
+ </p>
+ <figure src= "images/design/alt.design/line-area-6.png"
+ alt= "Columns after adding next footnote"/>
</section>
<section>
<title>Layout managers in the flow of control</title>
- <note>To be developed.</note>
+ <note>To be developed.</note>
</section>
</section>
- </body>
+ </body>
</document>
1.3 +189 -188 xml-fop/src/documentation/content/xdocs/design/alt.design/galleys.xml
Index: galleys.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/galleys.xml,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- galleys.xml 2 Dec 2002 12:00:11 -0000 1.2
+++ galleys.xml 18 Dec 2002 16:25:24 -0000 1.3
@@ -3,214 +3,215 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Galleys</title>
+ <header>
+ <title>Galleys</title>
<authors>
<person name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
<title>Layout galleys in FOP</title>
<section>
<title>Galleys in Lout</title>
- <p>
- Jeffrey H. Kingston, in <link href =
- "http://snark.niif.spb.su/~uwe/lout/design.pdf" ><em>The
- Design and Implementation of the Lout Document Formatting
- Language</em> Section 5</link>, describes the
- <strong>galley</strong> abstraction which he implemented in
- <em>Lout</em>. A document to be formatted is a stream of
- text and symbols, some of which are <strong>receptive
- symbols</strong>. The output file is the first receptive
- symbol; the formatting document is the first galley. The
- archetypical example of a receptive symbol is
- <strong>@FootPlace</strong> and its corresponding galley
- definition, <strong>@FootNote</strong>.
- </p>
- <p>
- Each galley should be thought of as a concurrent process, and
- each is associated with a semaphore (or synchronisation
- object.) Galleys are free to "promote" components into
- receptive targets as long as</p>
- <ul>
- <li>
- an appropriate target has been encountered in the file,
- </li>
- <li>
- the component being promoted contains no unresolved galley
- targets itself, and
- </li>
- <li>
- there is sufficient room for the galley component at the
- target.
- </li>
- </ul>
- <p>
- If these conditions are not met, the galley blocks on its
- semaphore. When conditions change so that further progress
- may be possible, the semaphore is signalled. Note that the
- galleys are a hierarchy, and that the processing and
- promotion of galley contents happens <em>bottom-up</em>.
- </p>
+ <p>
+ Jeffrey H. Kingston, in <link href =
+ "http://snark.niif.spb.su/~uwe/lout/design.pdf" ><em>The
+ Design and Implementation of the Lout Document Formatting
+ Language</em> Section 5</link>, describes the
+ <strong>galley</strong> abstraction which he implemented in
+ <em>Lout</em>. A document to be formatted is a stream of
+ text and symbols, some of which are <strong>receptive
+ symbols</strong>. The output file is the first receptive
+ symbol; the formatting document is the first galley. The
+ archetypical example of a receptive symbol is
+ <strong>@FootPlace</strong> and its corresponding galley
+ definition, <strong>@FootNote</strong>.
+ </p>
+ <p>
+ Each galley should be thought of as a concurrent process, and
+ each is associated with a semaphore (or synchronisation
+ object.) Galleys are free to "promote" components into
+ receptive targets as long as</p>
+ <ul>
+ <li>
+ an appropriate target has been encountered in the file,
+ </li>
+ <li>
+ the component being promoted contains no unresolved galley
+ targets itself, and
+ </li>
+ <li>
+ there is sufficient room for the galley component at the
+ target.
+ </li>
+ </ul>
+ <p>
+ If these conditions are not met, the galley blocks on its
+ semaphore. When conditions change so that further progress
+ may be possible, the semaphore is signalled. Note that the
+ galleys are a hierarchy, and that the processing and
+ promotion of galley contents happens <em>bottom-up</em>.
+ </p>
</section>
<section>
<title>Some features of galleys</title>
- <p>
- It is essential to note that galleys are self-managing; they
- are effectively layout <em>bots</em> which require only a
- receptive area. If a galley fills a receptive area (say, at
- the completion of a page), the galley will wait on its
- semaphore, and will remain stalled until a new receptive
- area is uncovered in the continued processing (say, as the
- filled page is flushed to output and a new empty page is
- generated.)
- </p>
- <p>
- Difficulties with this approach become evident when there
- are mutual dependencies between receptive areas which
- require negotiation between the respective galleys, and, in
- some cases, arbitrary deadlock breaking when there is no
- clear-cut resolution to conflicting demands. Footnote
- processing and side floats are examples. A thornier example
- is table column layout in <em>auto</em> mode, where the
- column widths are determined by the contents. In
- implementing galleys in FOP, these difficulties must be
- taken into account, and some solutions proposed.
- </p>
- <p>
- Galleys model the whole of the process of creating the final
- formatted output; the document as a whole is regarded as a
- galley which flushes in to the output file.
- </p>
+ <p>
+ It is essential to note that galleys are self-managing; they
+ are effectively layout <em>bots</em> which require only a
+ receptive area. If a galley fills a receptive area (say, at
+ the completion of a page), the galley will wait on its
+ semaphore, and will remain stalled until a new receptive
+ area is uncovered in the continued processing (say, as the
+ filled page is flushed to output and a new empty page is
+ generated.)
+ </p>
+ <p>
+ Difficulties with this approach become evident when there
+ are mutual dependencies between receptive areas which
+ require negotiation between the respective galleys, and, in
+ some cases, arbitrary deadlock breaking when there is no
+ clear-cut resolution to conflicting demands. Footnote
+ processing and side floats are examples. A thornier example
+ is table column layout in <em>auto</em> mode, where the
+ column widths are determined by the contents. In
+ implementing galleys in FOP, these difficulties must be
+ taken into account, and some solutions proposed.
+ </p>
+ <p>
+ Galleys model the whole of the process of creating the final
+ formatted output; the document as a whole is regarded as a
+ galley which flushes in to the output file.
+ </p>
</section>
<section>
<title>The layout tree</title>
- <anchor id="layout-tree"/>
- <p>
- This proposal for implementing galleys in FOP makes use of a
- <strong>layout tree</strong>. As with the <link href=
- "../layout.html" >layout managers</link><em></em> already
- proposed, the layout tree acts as a bridge between the <link
- href= "../fotree.html" >FO Tree</link> and the <link href=
- "../areas.html" >Area Tree</link>. If the elements of
- the FO Tree are FO nodes, and the elements of the Area Tree
- are Area nodes, representing areas to be drawn on the output
- medium, the elements of the layout tree are <strong>galley
- nodes</strong> and <strong>area tree fragments</strong>.
- The area tree fragments are the final stages of the
- resolution of the galleys; the output of the galleys will be
- inserted directly into the Area Tree. The tree structure
- makes it clear that the whole of the formatting process in
- FOP, under this model, is a hierarchical series of galleys.
- The dynamic data comes from fo:flow and fo:static-content,
- and the higher-level receptive areas are derived from the
- <em>layout-master-set</em>.
- </p>
+ <anchor id="layout-tree"/>
+ <p>
+ This proposal for implementing galleys in FOP makes use of a
+ <strong>layout tree</strong>. As with the <link href=
+ "../layout.html" >layout managers</link><em></em> already
+ proposed, the layout tree acts as a bridge between the <link
+ href= "../fotree.html" >FO Tree</link> and the <link href=
+ "../areas.html" >Area Tree</link>. If the elements of the
+ FO Tree are FO nodes, and the elements of the Area Tree are
+ Area nodes, representing areas to be drawn on the output
+ medium, the elements of the layout tree are <strong>galley
+ nodes</strong> and <strong>area tree fragments</strong>.
+ The area tree fragments are the final stages of the
+ resolution of the galleys; the output of the galleys will be
+ inserted directly into the Area Tree. The tree structure
+ makes it clear that the whole of the formatting process in
+ FOP, under this model, is a hierarchical series of galleys.
+ The dynamic data comes from fo:flow and fo:static-content,
+ and the higher-level receptive areas are derived from the
+ <em>layout-master-set</em>.
+ </p>
</section>
<section>
<title>Processing galleys</title>
- <p>
- Galleys are processed in two basic processing environments:
- </p>
- <section>
- <title>Inline- and block-progression dimensions known</title>
- <p>
- The galley at set-up is provided with both an
- <em>inline-progression-dimension</em> (<em>i-p-d</em>) and
- a <em>block-progression-dimension</em> (<em>b-p-d</em>).
- In this case, no further intervention is necessary to lay
- out the galley. The galley has the possibility of laying
- itself out, creating all necessary area nodes. This does
- not preclude the possibility that some children of this
- galley will not be able to be so directly laid out, and
- will fall into the second category.
- </p>
- <p>
- While the option of "automatic" layout exists, to use
- such a method would relinquish the possibility of
- monitoring the results of such layout and performing
- fine-tuning.
- </p>
- </section>
- <section>
- <title>Inline- ior block-progression-dimensions unknown</title>
- <p>
- The galley cannot immediately be provided with an i-p-d
- ior a b-p-d. This will occur in some of the difficult
- cases mentioned earlier. In these cases, the parent
- galley acts as a layout manager, similar to the sense used
- in <link href= "../layout.html" >another
- discussion</link>. The children, lacking full receptive
- area dimensions, will proceed with galley pre-processing,
- a procedure which will, of necessity, be followed
- recursively by all of its children down to the atomic
- elements of the galley. These atomic elements are the
- individual <em>fo:character</em> nodes and images of fixed
- dimensions.
- </p>
- </section>
+ <p>
+ Galleys are processed in two basic processing environments:
+ </p>
+ <section>
+ <title>Inline- and block-progression dimensions known</title>
+ <p>
+ The galley at set-up is provided with both an
+ <em>inline-progression-dimension</em> (<em>i-p-d</em>) and
+ a <em>block-progression-dimension</em> (<em>b-p-d</em>).
+ In this case, no further intervention is necessary to lay
+ out the galley. The galley has the possibility of laying
+ itself out, creating all necessary area nodes. This does
+ not preclude the possibility that some children of this
+ galley will not be able to be so directly laid out, and
+ will fall into the second category.
+ </p>
+ <p>
+ While the option of "automatic" layout exists, to use
+ such a method would relinquish the possibility of
+ monitoring the results of such layout and performing
+ fine-tuning.
+ </p>
+ </section>
+ <section>
+ <title>Inline- ior block-progression-dimensions unknown</title>
+ <p>
+ The galley cannot immediately be provided with an i-p-d
+ ior a b-p-d. This will occur in some of the difficult
+ cases mentioned earlier. In these cases, the parent
+ galley acts as a layout manager, similar to the sense used
+ in <link href= "../layout.html" >another
+ discussion</link>. The children, lacking full receptive
+ area dimensions, will proceed with galley pre-processing,
+ a procedure which will, of necessity, be followed
+ recursively by all of its children down to the atomic
+ elements of the galley. These atomic elements are the
+ individual <em>fo:character</em> nodes and images of fixed
+ dimensions.
+ </p>
+ </section>
</section>
<section>
<title>Galley pre-processing</title>
- <anchor id="pre-processing"/>
- <p>
- Galley pre-processing involves the spatial resolution of
- objects from the flows to the greatest extent possible
- without information on the dimensions of the target area.
- Line-areas have a block progression dimension which is
- determined by their contents. To achieve full generality in
- layouts of indeterminate dimensions, the contents of
- line-areas should be laid out as though their inline
- progression dimension were limited only by their content.
- In terms of inline-areas, galleys would process text and
- resolve the dimensions of included images. Text would be
- collected into runs with the same alignment
- characteristics. In the process, all possible "natural" and
- hyphenation break-points can be determined. Where a
- line-area contains mixed fonts or embedded images, the b-p-d
- of the individual line-areas which are eventually stacked
- will, in general, depend on the line break points, but the
- advantage of this approach is that such actual selections
- can be backed out and new break points selected with a
- minimum of re-calculation. This can potentially occur
- whenever a first attempt at page layout is backed out.
- <br/><br/>
- <strong>Figure 1</strong>
- </p>
- <figure src="images/design/alt.design/galley-preprocessing.png" alt="Galley
- pre-processing diagram"/>
- <p>
- Once this pre-processing has been achieved, it is
- envisaged that a layout manager might make requests to the
- galley of its ability to fill an area of a given
- inline-progression-dimension. A positive response would
- be accompanied by the block-progression-dimension. The
- other possibilities are a partial fill, which would also
- require b-p-d data, and a failure due to insufficient
- i-p-d, in which case the minimum i-p-d requirement would
- be returned. Note that decisions about the
- actual dimensions of line-areas to be filled can be
- deferred until all options have been tested.
- </p>
- <p>
- The other primary form of information provided by a
- pre-processed galley is its minimum and maximum i-p-d, so
- that decisions can be made by the parent on the spacing of
- table columns. Apart from information requests,
- higher-level processes can either make requests of the
- galleys for chunks of nominated sizes, or simply provide the
- galley with an i-p-d and b-p-d, which will trigger the
- flushing of the galley components into Area nodes. Until
- they have flushed, the galleys must be able to respond to a
- sequence of information requests, more or less in the manner
- of a request iterator, and separately manage the flushing of
- objects into the area tree. The purpose of the "request
- iterator" would be to support "incremental" information
- requests like <em>getNextBreakPosition</em>.
- </p>
+ <anchor id="pre-processing"/>
+ <p>
+ Galley pre-processing involves the spatial resolution of
+ objects from the flows to the greatest extent possible
+ without information on the dimensions of the target area.
+ Line-areas have a block progression dimension which is
+ determined by their contents. To achieve full generality in
+ layouts of indeterminate dimensions, the contents of
+ line-areas should be laid out as though their inline
+ progression dimension were limited only by their content.
+ In terms of inline-areas, galleys would process text and
+ resolve the dimensions of included images. Text would be
+ collected into runs with the same alignment
+ characteristics. In the process, all possible "natural" and
+ hyphenation break-points can be determined. Where a
+ line-area contains mixed fonts or embedded images, the b-p-d
+ of the individual line-areas which are eventually stacked
+ will, in general, depend on the line break points, but the
+ advantage of this approach is that such actual selections
+ can be backed out and new break points selected with a
+ minimum of re-calculation. This can potentially occur
+ whenever a first attempt at page layout is backed out.
+ <br/><br/>
+ <strong>Figure 1</strong>
+ </p>
+ <figure
+ src="images/design/alt.design/galley-preprocessing.png"
+ alt="Galley pre-processing diagram"/>
+ <p>
+ Once this pre-processing has been achieved, it is
+ envisaged that a layout manager might make requests to the
+ galley of its ability to fill an area of a given
+ inline-progression-dimension. A positive response would
+ be accompanied by the block-progression-dimension. The
+ other possibilities are a partial fill, which would also
+ require b-p-d data, and a failure due to insufficient
+ i-p-d, in which case the minimum i-p-d requirement would
+ be returned. Note that decisions about the
+ actual dimensions of line-areas to be filled can be
+ deferred until all options have been tested.
+ </p>
+ <p>
+ The other primary form of information provided by a
+ pre-processed galley is its minimum and maximum i-p-d, so
+ that decisions can be made by the parent on the spacing of
+ table columns. Apart from information requests,
+ higher-level processes can either make requests of the
+ galleys for chunks of nominated sizes, or simply provide the
+ galley with an i-p-d and b-p-d, which will trigger the
+ flushing of the galley components into Area nodes. Until
+ they have flushed, the galleys must be able to respond to a
+ sequence of information requests, more or less in the manner
+ of a request iterator, and separately manage the flushing of
+ objects into the area tree. The purpose of the "request
+ iterator" would be to support "incremental" information
+ requests like <em>getNextBreakPosition</em>.
+ </p>
</section>
</section>
- </body>
+ </body>
</document>
1.2 +100 -57 xml-fop/src/documentation/content/xdocs/design/alt.design/index.xml
Index: index.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/index.xml,v
retrieving revision 1.1
retrieving revision 1.2
diff -u -r1.1 -r1.2
--- index.xml 2 Dec 2002 10:19:43 -0000 1.1
+++ index.xml 18 Dec 2002 16:25:24 -0000 1.2
@@ -2,83 +2,126 @@
<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.1//EN"
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
+<!-- $Id$ -->
+
<document>
- <header>
+ <header>
<title>FOP Alternative Design</title>
<subtitle>Alternative Design Approach to FOP</subtitle>
<version>$Revision$ $Name$</version>
<authors>
<person name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+
+ <body>
<section>
<title>Alternative Design</title>
<p>
- This section of the FOP web site contains notes on approaches
- to an alternative design for FOP. The individual documents
- here are fragmentary, being notes of particular issues,
- without an overall framework as yet.
+ This section of the FOP web site contains notes on approaches
+ to an alternative design for FOP. The individual documents
+ here are fragmentary, being notes of particular issues,
+ without an overall framework as yet.
</p>
<p>
- The main aims of this redesign effort are:
+ The main aims of this redesign effort are:
</p>
<ul>
- <li>full conformance with the Recommendation</li>
- <li>increased performance</li>
- <li>reduced memory footprint</li>
- <li>no limitation on the size of files</li>
+ <li>full conformance with the Recommendation</li>
+ <li>no limitation on the size of files</li>
+ <li>increased performance</li>
+ <li>reduced memory footprint</li>
</ul>
<p>
- In order to achieve these aims, the primary areas
- of design interest are:
+ Secondary aims include:
</p>
<ul>
- <li>
- Representing properties, for most purposes, as integers.
- </li>
- <li>
- Distributing FOP processing over a number of threads with
- single-point downstream communication and flow control by
- means of traditional producer/consumer queues. The threads
- so far under consideration are:
- <ul>
- <li>XML parser</li>
- <li>FO tree builder</li>
- <li>layout engine</li>
- <li>Area tree builder</li>
- </ul>
- </li>
- <li>
- Representing trees with explicit Tree objects, rather than
- as implicit relationships among other objects.
- </li>
- <li>
- Caching integrated into the tree node access methods.
- </li>
+ <li>increased performance</li>
+ <li>reduced memory footprint</li>
+ </ul>
+ <p>
+ In order to achieve these aims, the primary areas
+ of design interest are:
+ </p>
+ <ul>
+ <li>
+ Representing properties, for most purposes, as integers.
+ </li>
+ <li>
+ Implementing a top-down processing model for each of the
+ processing components.
+ </li>
+ <li>
+ Distributing FOP processing over a number of threads with
+ single-point downstream communication and flow control by
+ means of traditional producer/consumer queues. The threads
+ so far under consideration are:
+ <ul>
+ <li>XML parser</li>
+ <li>FO tree builder</li>
+ <li>layout engine</li>
+ <li>Area tree builder</li>
+ </ul>
+ </li>
+ <li>
+ Redesigning XML parsing and FO tree building using a
+ <strong>pull-parsing</strong> methodology with integrated FO
+ input validation.
+ </li>
+ <li>
+ Representing vital relationships among the elements with
+ appropriate data structures. These include:
+ <ul>
+ <li>
+ Representing trees with explicit Tree objects, rather than
+ as implicit relationships among other objects.
+ </li>
+ <li>
+ Drawing threads through the tree nodes to
+ represent linear layout relationships for resolving
+ keeps, breaks and space specifiers.
+ </li>
+ </ul>
+ </li>
+ <li>
+ Caching integrated into the tree node access methods.
+ </li>
</ul>
<section>
- <title>Status and availability</title>
- <p>
- The <em>ALT DESIGN</em> effort is not taking place on the
- main line of development, represented by the <em>HEAD</em>
- tag on the CVS trunk. The source is available via the
- FOP_0-20-0_Alt-Design tag. This code has only a crude,
- non-<em>Ant</em> build environment, and is expected only to
- compile at this stage. Only the parser stage and the first
- stage of FO tree building is present. However, the first
- example of producer/consumer binding is working, the Tree
- class with inner Tree.Node and inner
- Tree.Node.<em>iterators</em> classes are available and
- working. Property handling is quite advanced, and is likely
- to be almost complete some time in July, 2002.
- </p>
- <p>
- Only <link href="mailto:pbwest@powerup.com.au">Peter
- West</link> is working on the ALT DESIGN sub-project.
- </p>
+ <title>Status and availability</title>
+ <p>
+ The <em>ALT DESIGN</em> effort is not taking place on the
+ main line of development, represented by the <em>HEAD</em>
+ tag on the CVS trunk. The source is available via the
+ FOP_0-20-0_Alt-Design tag. This code has only a
+ non-<em>Ant</em> build environment based on some small unix
+ shell scripts and the <em>jikes</em> compiler. The parser
+ stage and the FO tree building code is present. The first
+ example of producer/consumer binding is working, the Tree
+ class and the Node class with inner <em>iterator</em>
+ classes are available and working. Property handling is
+ almost complete, and all FO classes are present and
+ sufficiently complete to allow for FO tree building.
+ </p>
+ <p>
+ <link href=
+ "http://marc.theaimsgroup.com/%3Fl=fop-dev%26m=103890259919360%26w=2"
+ >Preliminary results</link> and <link href=
+ "http://marc.theaimsgroup.com/%3Fl=fop-dev%26m=103918886413611%26w=2"
+ >follow-up testing</link> of FO tree building shows memory
+ reductions of almost 50% compared to the most recently tuned
+ version of the maintenance version of the code (FOP 0.20.5
+ RC). Alt-Design FO tree building was also slightly faster,
+ in spite of the use of pull parsing implemented on top of
+ SAX.
+ </p>
+ <p>
+ Currently, only <link href="mailto:pbwest@powerup.com.au">Peter
+ West</link> is working on the ALT DESIGN sub-project.
+ </p>
</section>
</section>
- </body>
+
+ </body>
</document>
1.3 +89 -89 xml-fop/src/documentation/content/xdocs/design/alt.design/keeps.xml
Index: keeps.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/keeps.xml,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- keeps.xml 2 Dec 2002 12:00:11 -0000 1.2
+++ keeps.xml 18 Dec 2002 16:25:24 -0000 1.3
@@ -3,108 +3,108 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Keeps and breaks</title>
+ <header>
+ <title>Keeps and breaks</title>
<authors>
<person name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
<title>Keeps and breaks in layout galleys</title>
<p>
- The <link href= "galleys.html" >layout galleys</link> and the
- <link href= "galleys.html#layout-tree" >layout tree</link>
- which is their context have been discussed elsewhere. Here we
- discuss a possible method of implementing keeps and breaks
- within the context of layout galleys and the layout tree.
+ The <link href= "galleys.html" >layout galleys</link> and the
+ <link href= "galleys.html#layout-tree" >layout tree</link>
+ which is their context have been discussed elsewhere. Here we
+ discuss a possible method of implementing keeps and breaks
+ within the context of layout galleys and the layout tree.
</p>
<section>
<title>Breaks</title>
- <p>
- Breaks may be handled by inserting a column- or page-break
- pseudo-object into the galley stream. For break-before, the
- object would be inserted before the area in which the flow
- object, to which the property is attached, is leading. If
- the flow object is leading in no ancestor context, the
- pseudo-object is inserted before the object itself.
- Corresponding considerations apply for break-after.
- Selection of the position for these objects will be further
- examined in the discussion on keeps.
- </p>
+ <p>
+ Breaks may be handled by inserting a column- or page-break
+ pseudo-object into the galley stream. For break-before, the
+ object would be inserted before the area in which the flow
+ object, to which the property is attached, is leading. If
+ the flow object is leading in no ancestor context, the
+ pseudo-object is inserted before the object itself.
+ Corresponding considerations apply for break-after.
+ Selection of the position for these objects will be further
+ examined in the discussion on keeps.
+ </p>
</section>
<section>
<title>Keeps</title>
- <p>
- Conceptually, all keeps can be represented by a
- keep-together pseudo-area. The keep-together property
- itself is expressed during layout by wrapping all of the
- generated areas in a keep-together area. Keep-with-previous
- on formatting object A becomes a keep-together area spanning
- the first non-blank normal area leaf node, L, generated by A
- or its offspring, and the last non-blank normal area leaf
- node preceding L in the area tree. Likewise, keep-with-next
- on formatting object A becomes a keep-together area spanning
- the last non-blank normal area leaf node, L, generated by A
- or its offspring, and the first non-blank normal area leaf
- node following L in the area tree.
- <br/>TODO REWORK THIS for block vs inline
- </p>
- <p>
- The obvious problem with this arrangement is that the
- keep-together area violate the hierarachical arrangement of
- the layout tree. They form a concurrent structure focussed
- on the leaf nodes. This seems to be the essential problem
- of handling keep-with-(previous/next); that it cuts across
- the otherwise tree-structured flow of processing. Such
- problems are endemic in page layout.
- </p>
- <p>
- In any case, it seems that the relationships between areas
- that are of interest in keep processing need some form of
- direct expression, parallel to the layout tree itself.
- Restricting ourselves too block-level elements, and looking
- only at the simple block stacking cases, we get a diagram
- like the attached PNG. In order to track the relationships
- through the tree, we need four sets of links.
- </p>
- <p>
- <strong>Figure 1</strong>
- </p>
- <anchor id="Figure1"/>
- <figure src="images/design/alt.design/block-stacking.png" alt="Simple block-stacking
- diagram"/>
- <p>
- The three basic links are:
- </p>
- <ul>
- <!-- one of (dl sl ul ol li) -->
- <li>Leading edge to leading edge of first normal child.</li>
- <li>Trailing edge to leading edge of next normal
- sibling.</li>
- <li>Trailing edge to trailing edge of parent.</li>
- </ul>
- <p>
- Superimposed on the basic links are bridging links which
- span adjacent sets of links. These spanning links are the
- tree violators, and give direct access to the areas which
- are of interest in keep processing. They could be
- implemented as double-linked lists, either within the layout
- tree nodes or as separate structures. Gaps in the spanning
- links are joined by simply reproducing the single links, as
- in the diagram. The whole layout tree for a page is
- effectively threaded in order of interest, as far as keeps
- are concerned.
- </p>
- <p>
- The bonus of this structure is that it looks like a superset
- of the stacking constraints. It gives direct access to all
- sets of adjacent edges and sets of edges whose space
- specifiers need to be resolved. Fences can be easily enough
- detected during the process of space resolution.
- </p>
+ <p>
+ Conceptually, all keeps can be represented by a
+ keep-together pseudo-area. The keep-together property
+ itself is expressed during layout by wrapping all of the
+ generated areas in a keep-together area. Keep-with-previous
+ on formatting object A becomes a keep-together area spanning
+ the first non-blank normal area leaf node, L, generated by A
+ or its offspring, and the last non-blank normal area leaf
+ node preceding L in the area tree. Likewise, keep-with-next
+ on formatting object A becomes a keep-together area spanning
+ the last non-blank normal area leaf node, L, generated by A
+ or its offspring, and the first non-blank normal area leaf
+ node following L in the area tree.
+ <br/>TODO REWORK THIS for block vs inline
+ </p>
+ <p>
+ The obvious problem with this arrangement is that the
+ keep-together area violate the hierarachical arrangement of
+ the layout tree. They form a concurrent structure focussed
+ on the leaf nodes. This seems to be the essential problem
+ of handling keep-with-(previous/next); that it cuts across
+ the otherwise tree-structured flow of processing. Such
+ problems are endemic in page layout.
+ </p>
+ <p>
+ In any case, it seems that the relationships between areas
+ that are of interest in keep processing need some form of
+ direct expression, parallel to the layout tree itself.
+ Restricting ourselves too block-level elements, and looking
+ only at the simple block stacking cases, we get a diagram
+ like the attached PNG. In order to track the relationships
+ through the tree, we need four sets of links.
+ </p>
+ <p>
+ <strong>Figure 1</strong>
+ </p>
+ <anchor id="Figure1"/><figure src=
+ "images/design/alt.design/block-stacking.png" alt= "Simple
+ block-stacking diagram"/>
+ <p>
+ The three basic links are:
+ </p>
+ <ul>
+ <!-- one of (dl sl ul ol li) -->
+ <li>Leading edge to leading edge of first normal child.</li>
+ <li>Trailing edge to leading edge of next normal
+ sibling.</li>
+ <li>Trailing edge to trailing edge of parent.</li>
+ </ul>
+ <p>
+ Superimposed on the basic links are bridging links which
+ span adjacent sets of links. These spanning links are the
+ tree violators, and give direct access to the areas which
+ are of interest in keep processing. They could be
+ implemented as double-linked lists, either within the layout
+ tree nodes or as separate structures. Gaps in the spanning
+ links are joined by simply reproducing the single links, as
+ in the diagram. The whole layout tree for a page is
+ effectively threaded in order of interest, as far as keeps
+ are concerned.
+ </p>
+ <p>
+ The bonus of this structure is that it looks like a superset
+ of the stacking constraints. It gives direct access to all
+ sets of adjacent edges and sets of edges whose space
+ specifiers need to be resolved. Fences can be easily enough
+ detected during the process of space resolution.
+ </p>
</section>
</section>
- </body>
+ </body>
</document>
1.3 +119 -119 xml-fop/src/documentation/content/xdocs/design/alt.design/properties-classes.xml
Index: properties-classes.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/properties-classes.xml,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- properties-classes.xml 2 Dec 2002 12:00:11 -0000 1.2
+++ properties-classes.xml 18 Dec 2002 16:25:24 -0000 1.3
@@ -3,141 +3,141 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Properties$classes</title>
+ <header>
+ <title>Properties$classes</title>
<authors>
<person name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
<title>fo.Properties and the nested properties classes</title>
- <figure src="images/design/alt.design/PropertyClasses.png" alt="Nested property and
- top-level classes"/>
+ <figure src= "images/design/alt.design/PropertyClasses.png" alt=
+ "Nested property and top-level classes"/>
<section>
<title>Nested property classes</title>
- <p>
- Given the intention that individual properties have only a
- <em>virtual</em> instantiation in the arrays of
- <code>PropertyConsts</code>, these classes are intended to
- remain as repositories of static data and methods. The name
- of each property is entered in the
- <code>PropNames.propertyNames</code> array of
- <code>String</code>s, and each has a unique integer constant
- defined, corresponding to the offset of the property name in
- that array.
- </p>
- <section>
- <title>Fields common to all classes</title>
- <dl>
- <dt><code>final int dataTypes</code></dt>
- <dd>
- This field defines the allowable data types which may be
- assigned to the property. The value is chosen from the
- data type constants defined in <code>Properties</code>, and
- may consist of more than one of those constants,
- bit-ORed together.
- </dd>
- <dt><code>final int traitMapping</code></dt>
- <dd>
- This field defines the mapping of properties to traits
- in the <code>Area tree</code>. The value is chosen from the
- trait mapping constants defined in <code>Properties</code>,
- and may consist of more than one of those constants,
- bit-ORed together.
- </dd>
- <dt><code>final int initialValueType</code></dt>
- <dd>
- This field defines the data type of the initial value
- assigned to the property. The value is chosen from the
- initial value type constants defined in
- <code>Properties</code>.
- </dd>
- <dt><code>final int inherited</code></dt>
- <dd>
- This field defines the kind of inheritance applicable to
- the property. The value is chosen from the inheritance
- constants defined in <code>Properties</code>.
- </dd>
- </dl>
- </section>
- <section>
- <title>Datatype dependent fields</title>
- <dl>
- <dt>Enumeration types</dt>
- <dd>
- <strong><code>final String[] enums</code></strong><br/>
- This array contains the <code>NCName</code> text
- values of the enumeration. In the current
- implementation, it always contains a null value at
- <code>enum[0]</code>.<br/> <br/>
+ <p>
+ Given the intention that individual properties have only a
+ <em>virtual</em> instantiation in the arrays of
+ <code>PropertyConsts</code>, these classes are intended to
+ remain as repositories of static data and methods. The name
+ of each property is entered in the
+ <code>PropNames.propertyNames</code> array of
+ <code>String</code>s, and each has a unique integer constant
+ defined, corresponding to the offset of the property name in
+ that array.
+ </p>
+ <section>
+ <title>Fields common to all classes</title>
+ <dl>
+ <dt><code>final int dataTypes</code></dt>
+ <dd>
+ This field defines the allowable data types which may be
+ assigned to the property. The value is chosen from the
+ data type constants defined in <code>Properties</code>, and
+ may consist of more than one of those constants,
+ bit-ORed together.
+ </dd>
+ <dt><code>final int traitMapping</code></dt>
+ <dd>
+ This field defines the mapping of properties to traits
+ in the <code>Area tree</code>. The value is chosen from the
+ trait mapping constants defined in <code>Properties</code>,
+ and may consist of more than one of those constants,
+ bit-ORed together.
+ </dd>
+ <dt><code>final int initialValueType</code></dt>
+ <dd>
+ This field defines the data type of the initial value
+ assigned to the property. The value is chosen from the
+ initial value type constants defined in
+ <code>Properties</code>.
+ </dd>
+ <dt><code>final int inherited</code></dt>
+ <dd>
+ This field defines the kind of inheritance applicable to
+ the property. The value is chosen from the inheritance
+ constants defined in <code>Properties</code>.
+ </dd>
+ </dl>
+ </section>
+ <section>
+ <title>Datatype dependent fields</title>
+ <dl>
+ <dt>Enumeration types</dt>
+ <dd>
+ <strong><code>final String[] enums</code></strong><br/>
+ This array contains the <code>NCName</code> text
+ values of the enumeration. In the current
+ implementation, it always contains a null value at
+ <code>enum[0]</code>.<br/> <br/>
- <strong><code>final String[]
- enumValues</code></strong><br/> When the number of
- enumeration values is small,
- <code>enumValues</code> is a reference to the
- <code>enums</code> array.<br/> <br/>
+ <strong><code>final String[]
+ enumValues</code></strong><br/> When the number of
+ enumeration values is small,
+ <code>enumValues</code> is a reference to the
+ <code>enums</code> array.<br/> <br/>
- <strong><code>final HashMap
- enumValues</code></strong><br/> When the number of
- enumeration values is larger,
- <code>enumValues</code> is a
- <code>HashMap</code> statically initialized to
- contain the integer constant values corresponding to
- each text value, indexed by the text
- value.<br/> <br/>
+ <strong><code>final HashMap
+ enumValues</code></strong><br/> When the number of
+ enumeration values is larger,
+ <code>enumValues</code> is a
+ <code>HashMap</code> statically initialized to
+ contain the integer constant values corresponding to
+ each text value, indexed by the text
+ value.<br/> <br/>
- <strong><code>final int</code></strong>
- <em><code>enumeration-constants</code></em><br/> A
- unique integer constant is defined for each of the
- possible enumeration values.<br/> <br/>
- </dd>
- <dt>Many types:
- <code>final</code> <em>datatype</em>
- <code>initialValue</code></dt>
- <dd>
- When the initial datatype does not have an implicit
- initial value (as, for example, does type
- <code>AUTO</code>) the initial value for the property is
- assigned to this field. The type of this field will
- vary according to the <code>initialValueType</code>
- field.
- </dd>
- <dt>AUTO: <code>PropertyValueList auto(property,
- list)></code></dt>
- <dd>
- When <em>AUTO</em> is a legal value type, the
- <code>auto()</code> method must be defined in the property
- class.<br/>
- <em>NOT YET IMPLEMENTED.</em>
- </dd>
- <dt>COMPLEX: <code>PropertyValueList complex(property,
- list)></code></dt>
- <dd>
- <em>COMPLEX</em> is specified as a value type when complex
- conditions apply to the selection of a value type, or
- when lists of values are acceptable. To process and
- validate such a property value assignment, the
- <code>complex()</code> method must be defined in the
- property class.
- </dd>
- </dl>
- </section>
+ <strong><code>final int</code></strong>
+ <em><code>enumeration-constants</code></em><br/> A
+ unique integer constant is defined for each of the
+ possible enumeration values.<br/> <br/>
+ </dd>
+ <dt>Many types:
+ <code>final</code> <em>datatype</em>
+ <code>initialValue</code></dt>
+ <dd>
+ When the initial datatype does not have an implicit
+ initial value (as, for example, does type
+ <code>AUTO</code>) the initial value for the property is
+ assigned to this field. The type of this field will
+ vary according to the <code>initialValueType</code>
+ field.
+ </dd>
+ <dt>AUTO: <code>PropertyValueList auto(property,
+ list)></code></dt>
+ <dd>
+ When <em>AUTO</em> is a legal value type, the
+ <code>auto()</code> method must be defined in the property
+ class.<br/>
+ <em>NOT YET IMPLEMENTED.</em>
+ </dd>
+ <dt>COMPLEX: <code>PropertyValueList complex(property,
+ list)></code></dt>
+ <dd>
+ <em>COMPLEX</em> is specified as a value type when complex
+ conditions apply to the selection of a value type, or
+ when lists of values are acceptable. To process and
+ validate such a property value assignment, the
+ <code>complex()</code> method must be defined in the
+ property class.
+ </dd>
+ </dl>
+ </section>
</section>
<section>
<title>Nested property pseudo-classes</title>
- <p>
- The property pseudo-classes are classes, like
- <code>ColorCommon</code> which contain values, particularly
- <em>enums</em>, which are common to a number of actual
- properties.
- </p>
+ <p>
+ The property pseudo-classes are classes, like
+ <code>ColorCommon</code> which contain values, particularly
+ <em>enums</em>, which are common to a number of actual
+ properties.
+ </p>
</section>
<p>
- <strong>Previous:</strong> <link href= "classes-overview.html"
- >property classes overview.</link>
+ <strong>Previous:</strong> <link href= "classes-overview.html"
+ >property classes overview.</link>
</p>
</section>
- </body>
+ </body>
</document>
1.3 +155 -155 xml-fop/src/documentation/content/xdocs/design/alt.design/spaces.xml
Index: spaces.xml
===================================================================
RCS file: /home/cvs/xml-fop/src/documentation/content/xdocs/design/alt.design/spaces.xml,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- spaces.xml 2 Dec 2002 12:00:11 -0000 1.2
+++ spaces.xml 18 Dec 2002 16:25:24 -0000 1.3
@@ -3,177 +3,177 @@
"http://cvs.apache.org/viewcvs.cgi/*checkout*/xml-forrest/src/resources/schema/dtd/document-v11.dtd">
<document>
- <header>
- <title>Keeps and space-specifiers</title>
+ <header>
+ <title>Keeps and space-specifiers</title>
<authors>
<person name="Peter B. West" email="pbwest@powerup.com.au"/>
</authors>
- </header>
- <body>
+ </header>
+ <body>
<section>
<title>Keeps and space-specifiers in layout galleys</title>
<p>
- The <link href= "galleys.html" >layout galleys</link> and the
- <link href= "galleys.html#layout-tree" >layout tree</link>
- which is the context of this discussion have been discussed
- elsewhere. A <link href="keeps.html">previous document</link>
- discussed data structures which might facilitate the lining of
- blocks necessary to implement keeps. Here we discuss the
- similarities between the keep data structures and those
- required to implement space-specifier resolution.
+ The <link href= "galleys.html" >layout galleys</link> and the
+ <link href= "galleys.html#layout-tree" >layout tree</link>
+ which is the context of this discussion have been discussed
+ elsewhere. A <link href="keeps.html">previous document</link>
+ discussed data structures which might facilitate the lining of
+ blocks necessary to implement keeps. Here we discuss the
+ similarities between the keep data structures and those
+ required to implement space-specifier resolution.
</p>
<section>
<title>Space-specifiers</title>
- <note>
- <strong>4.3 Spaces and Conditionality</strong>
- ... Space-specifiers occurring in sequence may interact with
- each other. The constraint imposed by a sequence of
- space-specifiers is computed by calculating for each
- space-specifier its associated resolved space-specifier in
- accordance with their conditionality and precedence.
- </note>
- <note>
- 4.2.5 Stacking Constraints ... The intention of the
- definitions is to identify areas at any level of the tree
- which have only space between them.
- </note>
- <p>
- The quotations above are pivotal to understanding the
- complex discussion of spaces with which they are associated,
- all of which exists to enable the resolution of adjacent
- <space>s. It may be helpful to think of <em>stacking
- constraints</em> as <em><space>s interaction</em> or
- <em><space>s stacking interaction</em>.
- </p>
+ <note>
+ <strong>4.3 Spaces and Conditionality</strong>
+ ... Space-specifiers occurring in sequence may interact with
+ each other. The constraint imposed by a sequence of
+ space-specifiers is computed by calculating for each
+ space-specifier its associated resolved space-specifier in
+ accordance with their conditionality and precedence.
+ </note>
+ <note>
+ 4.2.5 Stacking Constraints ... The intention of the
+ definitions is to identify areas at any level of the tree
+ which have only space between them.
+ </note>
+ <p>
+ The quotations above are pivotal to understanding the
+ complex discussion of spaces with which they are associated,
+ all of which exists to enable the resolution of adjacent
+ <space>s. It may be helpful to think of <em>stacking
+ constraints</em> as <em><space>s interaction</em> or
+ <em><space>s stacking interaction</em>.
+ </p>
</section>
<section>
<title>Block stacking constraints</title>
- <p>
- In the discussion of block stacking constraints in Section
- 4.2.5, the notion of <em>fence</em> is introduced. For
- block stacking constraints, a fence is defined as either a
- reference-area boundary or a non-zero padding or border
- specification. Fences, however, do not come into play
- when determining the constraint between siblings. (See
- <link href="#Figure1">Figure 1</link>.)
- </p>
- <p><strong>Figure 1</strong></p><anchor id="Figure1"/>
- <figure src="images/design/alt.design/block-stacking-constraints.png"
- alt="block-stacking-constraints.png"/>
- <note>
- Figure 1 assumes a block-progression-direction of top to
- bottom.
- </note>
- <p>
- In <link href="#Figure1">Diagram a)</link>, block A has
- non-zero padding and borders, in addition to non-zero
- spaces. Note, however, that the space-after of A is
- adjacent to the space-before of block P, so borders and
- padding on these siblings have no impact on the interaction
- of their <space>s. The stacking constraint A,P is
- indicated by the red rectangle enclosing the space-after of
- A and the space-before of P.
- </p>
- <p>
- In <link href="#Figure1">Diagram b)</link>, block B is the
- first block child of P. The stacking constraint A,P is as
- before; the stacking constraint P,B is the space-before of
- B, as indicated by the enclosing magenta rectangle. In this
- case, however, the non-zero border of P prevents the
- interaction of the A,P and P,B stacking constraints. There
- is a <em>fence-before</em> P. The fence is notional; it has
- no precise location, as the diagram may lead one to believe.
- </p>
- <p>
- In <link href="#Figure1">Diagram c)</link>, because of the
- zero-width borders and padding on block P, the fence-before
- P is not present, and the adjacent <space>s of blocks
- A, P and B are free to interact. In this case, the stacking
- constraints A,P and P,B are as before, but now there is an
- additional stacking constraint A,B, represented by the light
- brown rectangle enclosing the other two stacking
- constraints.
- </p>
- <p>
- The other form of fence occurs when the parent block is a
- reference area. Diagram b) of <link href="#Figure2">Figure
- 2</link> illustrates this situation. Block C is a
- reference-area, involving a 180 degree change of
- block-progression-direction (BPD). In the diagram, the
- inner edge of block C represents the content rectangle, with
- its changed BPD. The thicker outer edge represents the
- outer boundary of the padding, border and spaces of C.
- </p>
- <p>
- While not every reference-area will change the
- inline-progression-direction (IPD) and BPD of an area, no
- attempt is made to discriminate these cases. A
- reference-area always a fence. The fence comes into play in
- analogous circumstances to non-zero borders or padding.
- Space resolution between a reference area and its siblings
- is not affected.
- </p>
- <p>
- In the case of <link href="#Figure2">Diagram b)</link>,
- these are block stacking constraints B,C and C,A. Within
- the reference-area, bock stacing constraints C,D and E,C are
- unaffected. However, the fence prevents block stacking
- constraints such as B,E or D,A. When there is a change of
- BPD, as <link href="#Figure2">Diagram b)</link> makes
- visually obvious, it is difficult to imagine which blocks
- would have such a constraint, and what the ordering of the
- constraint would be.
- </p>
- <p><strong>Figure 2</strong></p>
- <anchor id="Figure2"/>
- <figure src="images/design/alt.design/block-stacking-keeps.png"
- alt="block-stacking-keeps.png"/>
+ <p>
+ In the discussion of block stacking constraints in Section
+ 4.2.5, the notion of <em>fence</em> is introduced. For
+ block stacking constraints, a fence is defined as either a
+ reference-area boundary or a non-zero padding or border
+ specification. Fences, however, do not come into play
+ when determining the constraint between siblings. (See
+ <link href="#Figure1">Figure 1</link>.)
+ </p>
+ <p><strong>Figure 1</strong></p><anchor id="Figure1"/> <figure
+ src= "images/design/alt.design/block-stacking-constraints.png"
+ alt= "block-stacking-constraints.png"/>
+ <note>
+ Figure 1 assumes a block-progression-direction of top to
+ bottom.
+ </note>
+ <p>
+ In <link href="#Figure1">Diagram a)</link>, block A has
+ non-zero padding and borders, in addition to non-zero
+ spaces. Note, however, that the space-after of A is
+ adjacent to the space-before of block P, so borders and
+ padding on these siblings have no impact on the interaction
+ of their <space>s. The stacking constraint A,P is
+ indicated by the red rectangle enclosing the space-after of
+ A and the space-before of P.
+ </p>
+ <p>
+ In <link href="#Figure1">Diagram b)</link>, block B is the
+ first block child of P. The stacking constraint A,P is as
+ before; the stacking constraint P,B is the space-before of
+ B, as indicated by the enclosing magenta rectangle. In this
+ case, however, the non-zero border of P prevents the
+ interaction of the A,P and P,B stacking constraints. There
+ is a <em>fence-before</em> P. The fence is notional; it has
+ no precise location, as the diagram may lead one to believe.
+ </p>
+ <p>
+ In <link href="#Figure1">Diagram c)</link>, because of the
+ zero-width borders and padding on block P, the fence-before
+ P is not present, and the adjacent <space>s of blocks
+ A, P and B are free to interact. In this case, the stacking
+ constraints A,P and P,B are as before, but now there is an
+ additional stacking constraint A,B, represented by the light
+ brown rectangle enclosing the other two stacking
+ constraints.
+ </p>
+ <p>
+ The other form of fence occurs when the parent block is a
+ reference area. Diagram b) of <link href="#Figure2">Figure
+ 2</link> illustrates this situation. Block C is a
+ reference-area, involving a 180 degree change of
+ block-progression-direction (BPD). In the diagram, the
+ inner edge of block C represents the content rectangle, with
+ its changed BPD. The thicker outer edge represents the
+ outer boundary of the padding, border and spaces of C.
+ </p>
+ <p>
+ While not every reference-area will change the
+ inline-progression-direction (IPD) and BPD of an area, no
+ attempt is made to discriminate these cases. A
+ reference-area always a fence. The fence comes into play in
+ analogous circumstances to non-zero borders or padding.
+ Space resolution between a reference area and its siblings
+ is not affected.
+ </p>
+ <p>
+ In the case of <link href="#Figure2">Diagram b)</link>,
+ these are block stacking constraints B,C and C,A. Within
+ the reference-area, bock stacing constraints C,D and E,C are
+ unaffected. However, the fence prevents block stacking
+ constraints such as B,E or D,A. When there is a change of
+ BPD, as <link href="#Figure2">Diagram b)</link> makes
+ visually obvious, it is difficult to imagine which blocks
+ would have such a constraint, and what the ordering of the
+ constraint would be.
+ </p>
+ <p><strong>Figure 2</strong></p>
+ <anchor id="Figure2"/>
+ <figure src= "images/design/alt.design/block-stacking-keeps.png"
+ alt= "block-stacking-keeps.png"/>
</section>
<section>
<title>Keep relationships between blocks</title>
- <p>
- As complicated as space-specifiers become when
- reference-areas are involved, the keep relationships as
- described in the <link
- href="keeps.html#Figure1">keeps</link> document, are
- unchanged. This is also illustrated in <link
- href="#Figure2">Figure 2</link>. Diagram b) shows the
- relative placement of blocks in the rendered output when a
- 180 degree change of BPD occurs, with blocks D and E
- stacking in the reverse direction to blocks B and C.
- Diagram c) shows what happens when the page is too short to
- accommodate the last block. D is still laid out, but E is
- deferred to the next page.
- </p>
- <p>
- Note that this rendering reality is expressed directly in
- the area (and layout) tree view. Consequently, any keep
- relationships expressed as links threading through the
- layout tree will not need to be modified to account for
- reference-area boundaries, as is the case with similar
- space-specifier edge links. E.g., a keep-with-next
- condition on block B can be resolved along the path of these
- links (B->C->D) into a direct relationship of B->D,
- irrespective of the reference-area boundary.
- </p>
- <p>
- While the same relationships obviously hold when a reference
- area induces no change of BPD, the situation for BPD changes
- perpendicular to the parent's BPD may not be so clear. In
- general, it probably does not make much sense to impose keep
- conditions across such a boundary, but there seems to be
- nothing preventing such conditions. They can be dealt with
- in the same way, i.e., the next leaf block linked in area
- tree order must be the next laid out. If a keep condition
- is in place, an attempt must be made to meet it. A number
- of unusual considerations would apply, e.g. the minimum
- inline-progression-dimension of the first leaf block within
- the reference-area as compared to the minimum IPD of
- subsequent blocks, but <em>prima facie</em>, the essential
- logic of the keeps links remains.
- </p>
+ <p>
+ As complicated as space-specifiers become when
+ reference-areas are involved, the keep relationships as
+ described in the <link
+ href="keeps.html#Figure1">keeps</link> document, are
+ unchanged. This is also illustrated in <link
+ href="#Figure2">Figure 2</link>. Diagram b) shows the
+ relative placement of blocks in the rendered output when a
+ 180 degree change of BPD occurs, with blocks D and E
+ stacking in the reverse direction to blocks B and C.
+ Diagram c) shows what happens when the page is too short to
+ accommodate the last block. D is still laid out, but E is
+ deferred to the next page.
+ </p>
+ <p>
+ Note that this rendering reality is expressed directly in
+ the area (and layout) tree view. Consequently, any keep
+ relationships expressed as links threading through the
+ layout tree will not need to be modified to account for
+ reference-area boundaries, as is the case with similar
+ space-specifier edge links. E.g., a keep-with-next
+ condition on block B can be resolved along the path of these
+ links (B->C->D) into a direct relationship of B->D,
+ irrespective of the reference-area boundary.
+ </p>
+ <p>
+ While the same relationships obviously hold when a reference
+ area induces no change of BPD, the situation for BPD changes
+ perpendicular to the parent's BPD may not be so clear. In
+ general, it probably does not make much sense to impose keep
+ conditions across such a boundary, but there seems to be
+ nothing preventing such conditions. They can be dealt with
+ in the same way, i.e., the next leaf block linked in area
+ tree order must be the next laid out. If a keep condition
+ is in place, an attempt must be made to meet it. A number
+ of unusual considerations would apply, e.g. the minimum
+ inline-progression-dimension of the first leaf block within
+ the reference-area as compared to the minimum IPD of
+ subsequent blocks, but <em>prima facie</em>, the essential
+ logic of the keeps links remains.
+ </p>
</section>
</section>
- </body>
+ </body>
</document>
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