viewBox: distorted text?

[sp...@chezphil.org]

Hi FOP people,

A recent message indicated that viewBox on SVG should now work, so
I've taken out the kludgey work-around that I previously used to cope
with not having this. And yes it does - nearly - work.  But it looks
to me as if there's some sort of strange rounding going on in the
coordinates.  I don't get this when I render the same SVG source to
bitmaps using Batik's rasteriser, or when I run FOP with -awt, so I
reckon the problem is in the PDF code.

There's an example below.  This shows the same SVG fragment four
times.  It contains a single svg:text item.  The first time, this is
unmodified and comes out distorted: it looks like some coordinates
have been slightly displaced or rounded.  [If it's not distorted for
you, please let me know!]

Assuming that this was something getting rounded to an integer when it
shouldn't be I scaled the viewbox by 10 and put a
transform="scale(10)" around the contents.  This is the second
example, and it looks fine.  Scaling by 100 in the third example also
works.  But when I scale by 1000, in the fourth example, the image is
reduced to a single point!  Unfortunately there isn't a single scale
factor that works for all of my SVG source files.

Any ideas what's up?  I'm using FOP 0.20.2, using the Sun JRE version
1.3.1, and I get similar results on Solaris and Windows.  The shapes
of the distorted characters differ on the different platforms,
presumably because the fonts are different.

Here's the code:

<?xml version="1.0" encoding="UTF-8"?>
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format">
  <fo:layout-master-set>
    <fo:simple-page-master margin-right="25mm" margin-left="25mm"
                           margin-bottom="20mm" margin-top="15mm"
                           page-height="297mm" page-width="210mm"
                           master-name="a4">
      <fo:region-before extent="10mm"/>
      <fo:region-after extent="10mm"/>
      <fo:region-body margin-bottom="15mm" margin-top="15mm"/>
    </fo:simple-page-master>
  </fo:layout-master-set>
  <fo:page-sequence master-name="a4">
    <fo:flow flow-name="xsl-region-body">

    <fo:block>
      <fo:instream-foreign-object>
        <svg:svg xmlns:svg="http://www.w3.org/2000/svg"
                 fill="none" width="5cm" height="1cm"
                 viewBox="0 0 5.0 1.0"
                 preserveAspectRatio="xMidYMid meet"
                 contentScriptType="text/ecmascript"
                 contentStyleType="text/css">
            <svg:text fill="#000000" text-anchor="start" font-size="0.3"
                      x="0.1" y="0.2">x1: Hello World</svg:text>
        </svg:svg>
      </fo:instream-foreign-object>
    </fo:block>

    <fo:block>
      <fo:instream-foreign-object>
        <svg:svg xmlns:svg="http://www.w3.org/2000/svg"
                 fill="none" width="5cm" height="1cm"
                 viewBox="0 0 50.0 10.0"
                 preserveAspectRatio="xMidYMid meet"
                 contentScriptType="text/ecmascript"
                 contentStyleType="text/css">
          <svg:g transform="scale(10.0)">
            <svg:text fill="#000000" text-anchor="start" font-size="0.3"
                      x="0.1" y="0.2">x10: Hello World</svg:text>
          </svg:g>
        </svg:svg>
      </fo:instream-foreign-object>
    </fo:block>

    <fo:block>
      <fo:instream-foreign-object>
        <svg:svg xmlns:svg="http://www.w3.org/2000/svg"
                 fill="none" width="5cm" height="1cm"
                 viewBox="0 0 500 100"
                 preserveAspectRatio="xMidYMid meet"
                 contentScriptType="text/ecmascript"
                 contentStyleType="text/css">
          <svg:g transform="scale(100)">
            <svg:text fill="#000000" text-anchor="start" font-size="0.3"
                      x="0.1" y="0.2">x100: Hello World</svg:text>
          </svg:g>
        </svg:svg>
      </fo:instream-foreign-object>
    </fo:block>

      <fo:instream-foreign-object>
        <svg:svg xmlns:svg="http://www.w3.org/2000/svg"
                 fill="none" width="5cm" height="1cm"
                 viewBox="0 0 5000 1000"
                 preserveAspectRatio="xMidYMid meet"
                 contentScriptType="text/ecmascript"
                 contentStyleType="text/css">
          <svg:g transform="scale(1000)">
            <svg:text fill="#000000" text-anchor="start" font-size="0.3"
                      x="0.1" y="0.2">x1000: Hello World</svg:text>
          </svg:g>
        </svg:svg>
      </fo:instream-foreign-object>

    </fo:flow>
  </fo:page-sequence>
</fo:root>


Thanks for your attention.

--Phil.


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