tor-browser

commit 2d8fef47e55b10b5ecd2cc151a72c9d632b43773
parent 271b5ba4ac199f3b2981fc9f0a62bc4ba9da31d5
Author: longsonr <longsonr@gmail.com>
Date:   Tue, 25 Nov 2025 12:05:28 +0000

Bug 2000458 - getExtentOfChar should take dominant-baseline into account r=jwatt

Differential Revision: https://phabricator.services.mozilla.com/D273725

Diffstat:
M
layout/svg/SVGTextFrame.cpp
 | 
17
++++++++++++++---
M
testing/web-platform/tests/svg/text/scripted/getextentofchar.html
 | 
10
+++++++++-

2 files changed, 23 insertions(+), 4 deletions(-)
diff --git a/layout/svg/SVGTextFrame.cpp b/layout/svg/SVGTextFrame.cpp
@@ -259,7 +259,8 @@ static bool IsGlyphPositioningAttribute(nsAtom* aAttribute) {
  * @param aTextRun The text run of aFrame.
  * @param aDominantBaseline The dominant-baseline value to use.
  */
-static nscoord GetBaselinePosition(nsTextFrame* aFrame, gfxTextRun* aTextRun,
+static nscoord GetBaselinePosition(nsTextFrame* aFrame,
+                                   const gfxTextRun* aTextRun,
                                    StyleDominantBaseline aDominantBaseline,
                                    float aFontSizeScaleFactor) {
   WritingMode writingMode = aFrame->GetWritingMode();
@@ -2080,6 +2081,13 @@ class MOZ_STACK_CLASS CharIterator {
   bool IsAfterSubtree() const { return mFrameIterator.IsAfterSubtree(); }
 
   /**
+   * Returns the iterator's computed dominant-baseline value.
+   */
+  StyleDominantBaseline DominantBaseline() const {
+    return mFrameIterator.DominantBaseline();
+  }
+
+  /**
    * Returns whether the current character is a skipped character.
    */
   bool IsOriginalCharSkipped() const {
@@ -4028,15 +4036,18 @@ already_AddRefed<SVGRect> SVGTextFrame::GetExtentOfChar(nsIContent* aContent,
   m.PreRotate(mPositions[startIndex].mAngle);
   m.PreScale(1 / mFontSizeScaleFactor, 1 / mFontSizeScaleFactor);
 
+  nscoord baseline = GetBaselinePosition(
+      textFrame, textRun, it.DominantBaseline(), mFontSizeScaleFactor);
+
   gfxRect glyphRect;
   if (textRun->IsVertical()) {
     glyphRect = gfxRect(
-        -presContext->AppUnitsToGfxUnits(descent) * cssPxPerDevPx, x,
+        -presContext->AppUnitsToGfxUnits(baseline) * cssPxPerDevPx, x,
         presContext->AppUnitsToGfxUnits(ascent + descent) * cssPxPerDevPx,
         advance);
   } else {
     glyphRect = gfxRect(
-        x, -presContext->AppUnitsToGfxUnits(ascent) * cssPxPerDevPx, advance,
+        x, -presContext->AppUnitsToGfxUnits(baseline) * cssPxPerDevPx, advance,
         presContext->AppUnitsToGfxUnits(ascent + descent) * cssPxPerDevPx);
   }
 
diff --git a/testing/web-platform/tests/svg/text/scripted/getextentofchar.html b/testing/web-platform/tests/svg/text/scripted/getextentofchar.html
@@ -5,8 +5,9 @@
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 
-<svg width="800" height="600">
+<svg width="800" height="200">
 <text><tspan id="tspan1" x="50 150 100" y="100">abc</tspan></text>
+<text dominant-baseline="hanging"><tspan id="tspan2" x="50" y="150">abc</tspan></text>
 </svg>
 
 <script>
@@ -17,4 +18,11 @@ test(() => {
   assert_equals(element.getExtentOfChar(1).x, 150);
   assert_equals(element.getExtentOfChar(2).x, 100);
 }, 'Multiple chunks in a tspan');
+
+test(() => {
+  const element = document.querySelector('#tspan2');
+  assert_equals(element.getNumberOfChars(), 3);
+  assert_equals(element.getExtentOfChar(0).x, 50);
+  assert_approx_equals(element.getExtentOfChar(0).y, 147.5, 1);
+}, 'With dominant-baseline');
 </script>