[XML Graphics - FOP Wiki] Updated: PageLayout

[fo...@xml.apache.org]

   Date: 2005-03-01T00:54:54
   Editor: 81.221.219.138
   Wiki: XML Graphics - FOP Wiki
   Page: PageLayout
   URL: http://wiki.apache.org/xmlgraphics-fop/PageLayout

   Comment on look-ahead strategies

Change Log:

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@@ -138,7 +138,7 @@
 stretchability/shrinkability on the page. This strategy is used by TeX
 in its vertical list.
 
-The next possible strategy uses look ahead. There is a sliding window
+The next possible strategy uses look ahead [1]. There is a sliding window
 of ''N'' pages. The best page breaks are calculated over all pages in the
 window, but only the page break of the first page is used. Then the
 window is moved forward one page, and the effort is repeated. This
@@ -151,6 +151,17 @@
 A total-fit strategy, as used in paragraph breaking, can only be
 applied to a complete page sequence. This will almost always to
 expensive, both in computing effort and in memory requirements.
+
+----
+
+''[1] JM: One problem I see with a look-ahead approach is the different 
+available IPD value on subsequent pages which would cause too much 
+recalculation of the lines (and table layouts if auto-layout is active). 
+In line-breaking we only have constant boxes while in page-breaking the 
+boxes have different dimensions due to other line breaking decisions 
+being made. Too much look ahead can cause too much wasted effort in 
+complex documents. (See 
+[http://cvs.apache.org/viewcvs.cgi/xml-fop/test/layoutengine/testcases/normal-breaking4.xml normal-breaking4.xml])''
 
 == Layout around a page break ==
 

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