(#129): Fix baseline-shift for simple subscripts/superscripts and absolute offsets

This has two parts:

1. Start a new chunk for a tspan even if it does not have absolute
positions.  This is so that

  <text>
    Foo bar<tspan baseline-shift="sub">subscript</tspan>
  </text>

will actually pick up the span's ComputedValues - note how the tspan
does not have x/y position properties.

2. If the baseline-shift is a length with an absolute unit, add it to
the parent's instead of ignoring it.  As a limitation, we still use
only the parent's baseline-shift if the units are different.

Fixes https://gitlab.gnome.org/GNOME/librsvg/-/issues/129

2 files changed, 71 insertions, 0 deletions

diff --git a/tests/fixtures/reftests/svg1.1/text-align-02-b-ref.png b/tests/fixtures/reftests/svg1.1/text-align-02-b-ref.png
new file mode 100644
index 00000000..b9e67243
--- /dev/null
+++ b/tests/fixtures/reftests/svg1.1/text-align-02-b-ref.png
diff --git a/tests/fixtures/reftests/svg1.1/text-align-02-b.svg b/tests/fixtures/reftests/svg1.1/text-align-02-b.svg
new file mode 100644
index 00000000..d172d84c
--- /dev/null
+++ b/tests/fixtures/reftests/svg1.1/text-align-02-b.svg
@@ -0,0 +1,71 @@
+<svg version="1.1" baseProfile="basic" id="svg-root"
+  width="100%" height="100%" viewBox="0 0 480 360"
+  xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+  <!--======================================================================-->
+  <!--=  SVG 1.1 2nd Edition Test Case                                     =-->
+  <!--======================================================================-->
+  <!--=  Copyright 2009 World Wide Web Consortium, (Massachusetts          =-->
+  <!--=  Institute of Technology, European Research Consortium for         =-->
+  <!--=  Informatics and Mathematics (ERCIM), Keio University).            =-->
+  <!--=  All Rights Reserved.                                              =-->
+  <!--=  See http://www.w3.org/Consortium/Legal/.                          =-->
+  <!--======================================================================-->
+  <d:SVGTestCase xmlns:d="http://www.w3.org/2000/02/svg/testsuite/description/"
+    template-version="1.4" reviewer="SVGWG" author="Jon Ferraiolo" status="accepted"
+    version="$Revision: 1.8 $" testname="$RCSfile: text-align-02-b.svg,v $">
+    <d:testDescription xmlns="http://www.w3.org/1999/xhtml" href="http://www.w3.org/TR/SVG11/text.html#AlignmentProperties">
+      <p>
+        Test the 'baseline-shift' property (horizontal).
+      </p>
+    </d:testDescription>
+    <d:operatorScript xmlns="http://www.w3.org/1999/xhtml">
+      <p>
+        Run the test. No interaction required.
+      </p>
+    </d:operatorScript>
+    <d:passCriteria xmlns="http://www.w3.org/1999/xhtml">
+      <p>
+        This three lines test property 'baseline-shift'.
+        The first line tests 'baseline-shift:7' (i.e., a length for 'baseline-shift').
+        The pink text should be shifted upwards by an amount approximately half of the height of the text.
+        The second line tests 'baseline-shift:-70%' (i.e., a percentage for 'baseline-shift').
+        The pink text should shift downward by about the height of the text.
+        The third line tests the three keywords 'sub', 'super' and 'normal'.
+        The string "sub" should be shifted downwards, the string "super" shifted upwards,
+        and the string "te" (in blue) aligned with the remainder of the text in the line.
+      </p>
+    </d:passCriteria>
+  </d:SVGTestCase>
+  <title id="test-title">$RCSfile: text-align-02-b.svg,v $</title>
+  <defs>
+    <font-face font-family="SVGFreeSansASCII" unicode-range="U+0-7F">
+      <font-face-src>
+        <font-face-uri xlink:href="../resources/SVGFreeSans.svg#ascii"/>
+      </font-face-src>
+    </font-face>
+  </defs>
+  <g id="test-body-content" font-family="SVGFreeSansASCII,sans-serif" font-size="18">
+    <text font-size="34" x="5" y="40">Test 'baseline-shift' (horizontal)</text>
+    <g id="baseline-shift" font-size="30" transform="translate(15,120)">
+      <text y="0">
+        Normal<tspan baseline-shift="7" fill="fuchsia">baseline-shift:7</tspan>text
+      </text>
+      <text y="70">
+        Normal<tspan baseline-shift="-70%" fill="fuchsia">baseline-shift:-70%</tspan>text
+      </text>
+      <text y="140">
+        Normal<tspan baseline-shift="sub" fill="fuchsia">sub</tspan><tspan baseline-shift="super" fill="green">super</tspan><tspan baseline-shift="baseline" fill="blue">te</tspan>xt
+      </text>
+    </g>
+  </g>
+  <g font-family="SVGFreeSansASCII,sans-serif" font-size="32">
+    <text id="revision" x="10" y="340" stroke="none" fill="black">$Revision: 1.8 $</text>
+  </g>
+  <rect id="test-frame" x="1" y="1" width="478" height="358" fill="none" stroke="#000000"/>
+  <!-- comment out this watermark once the test is approved -->
+  <!--<g id="draft-watermark">
+    <rect x="1" y="1" width="478" height="20" fill="red" stroke="black" stroke-width="1"/>
+    <text font-family="SVGFreeSansASCII,sans-serif" font-weight="bold" font-size="20" x="240"
+      text-anchor="middle" y="18" stroke-width="0.5" stroke="black" fill="white">DRAFT</text>
+  </g>-->
+</svg>