Bug 1730049 - correct dominant-baseline for vertical-rl r=jfkthame

Differential Revision: https://phabricator.services.mozilla.com/D125371

layout/reftests/svg/reftest.list

@@ -490,6 +490,7 @@ fuzzy-if(cocoaWidget&&layersGPUAccelerated,0-1,0-3) random-if(/^Windows\x20NT\x2
 random-if(/^Windows\x20NT\x206\.1/.test(http.oscpu)) == text-layout-07.svg text-layout-07-ref.svg # Bug 1392106
 random-if(/^Windows\x20NT\x206\.1/.test(http.oscpu)) == text-layout-08.svg text-layout-08-ref.svg # Bug 1392106
 random-if(/^Windows\x20NT\x206\.1/.test(http.oscpu)) == text-layout-09.svg pass.svg # Bug 1392106
+random-if(/^Windows\x20NT\x206\.1/.test(http.oscpu)) == text-layout-10.svg pass.svg # Bug 1392106
 random-if(/^Windows\x20NT\x206\.1/.test(http.oscpu)) == text-scale-01.svg text-scale-01-ref.svg # Bug 1392106
 fuzzy-if(skiaContent,0-2,0-1000) random-if(/^Windows\x20NT\x206\.1/.test(http.oscpu)) == text-scale-02.svg text-scale-02-ref.svg # Bug 1392106
 random-if(/^Windows\x20NT\x206\.1/.test(http.oscpu)) == text-scale-03.svg text-scale-03-ref.svg # Bug 1392106

layout/reftests/svg/text-layout-09.svg

@@ -20,9 +20,11 @@
   }
   ]]></style>
   <script>
-  function cover(element) {
+  function cover(id, offset) {
+    let element = document.getElementById(id);
+    element.dy.baseVal[0].value = offset;
     let rect = document.createElementNS("http://www.w3.org/2000/svg", "rect");
-    let bbox = element.getBBox(); 
+    let bbox = element.getBBox();
     rect.x.baseVal.value = bbox.x;
     rect.y.baseVal.value = bbox.y;
     rect.width.baseVal.value = bbox.width;
@@ -37,13 +39,9 @@
     let text = 'h';
     let textMetrics = ctx.measureText(text);
 
-    let hanging = document.getElementById("hanging");
-    hanging.dy.baseVal[0].value = textMetrics.actualBoundingBoxAscent * 1.1;
-    cover(hanging);
+    cover("hanging", textMetrics.actualBoundingBoxAscent * 1.1);
 
-    let mathematical = document.getElementById("mathematical");
-    mathematical.dy.baseVal[0].value = textMetrics.actualBoundingBoxAscent / 2 * 1.4;
-    cover(mathematical);
+    cover("mathematical", textMetrics.actualBoundingBoxAscent / 2 * 1.4);
 
     document.documentElement.removeAttribute('class');
   }

layout/reftests/svg/text-layout-10.svg

@@ -0,0 +1,66 @@
+<svg width="100%" height="100%" xmlns="http://www.w3.org/2000/svg" class="reftest-wait">
+
+  <foreignObject><canvas xmlns="http://www.w3.org/1999/xhtml" id="canvas"/></foreignObject>
+
+  <rect width="100%" height="100%" fill="lime"/>
+
+  <g fill="red">
+    <text dominant-baseline="alphabetic" x="10" y="20">Alphabetic</text>
+    <text dominant-baseline="auto" x="80" y="20">Auto</text>
+    <text dominant-baseline="middle" x="150" y="20">Middle</text>
+    <text dominant-baseline="hanging" x="220" y="20">Hanging</text>
+    <text dominant-baseline="central" x="290" y="20">Central</text>
+    <text dominant-baseline="mathematical" x="360" y="20">Mathematical</text>
+  </g>
+
+  <g fill="lime">
+    <text id="alphabetic" dominant-baseline="text-before-edge" x="10" y="20" dx="0">Alphabetic</text>
+    <text id="auto" dominant-baseline="text-before-edge" x="80" y="20" dx="0">Auto</text>
+    <text id="middle" dominant-baseline="text-before-edge" x="150" y="20" dx="0">Middle</text>
+    <text id="hanging" dominant-baseline="text-before-edge" x="220" y="20" dx="0">Hanging</text>
+    <text id="central" dominant-baseline="text-before-edge" x="290" y="20" dx="0">Central</text>
+    <text id="mathematical" dominant-baseline="text-before-edge" x="360" y="20" dx="0">Mathematical</text>
+  </g>
+
+  <style><![CDATA[
+  text {
+    font: bold 30px Verdana, Helvetica, Arial, sans-serif;
+    writing-mode: vertical-rl;
+  }
+  ]]></style>
+  <script>
+  function cover(id, offset) {
+    let element = document.getElementById(id);
+    element.dx.baseVal[0].value = offset;
+    let rect = document.createElementNS("http://www.w3.org/2000/svg", "rect");
+    let bbox = element.getBBox();
+    rect.x.baseVal.value = bbox.x;
+    rect.y.baseVal.value = bbox.y;
+    rect.width.baseVal.value = bbox.width;
+    rect.height.baseVal.value = bbox.height;
+    element.parentElement.appendChild(rect);
+  }
+  onload = function() {
+    const canvas = document.getElementById('canvas');
+    const ctx = canvas.getContext('2d');
+    ctx.font = 'bold 30px Verdana, Helvetica, Arial, sans-serif';
+
+    let text = 'h';
+    let textMetrics = ctx.measureText(text);
+
+    cover("alphabetic", textMetrics.actualBoundingBoxAscent);
+
+    cover("auto", textMetrics.actualBoundingBoxAscent);
+
+    cover("middle", textMetrics.actualBoundingBoxAscent * 0.7);
+
+    cover("hanging", textMetrics.actualBoundingBoxAscent * 0.2);
+
+    cover("central", textMetrics.actualBoundingBoxAscent);
+
+    cover("mathematical", textMetrics.actualBoundingBoxAscent / 2);
+
+    document.documentElement.removeAttribute('class');
+  }
+  </script>
+</svg>

layout/svg/SVGTextFrame.cpp

@@ -283,24 +283,31 @@ static nscoord GetBaselinePosition(nsTextFrame* aFrame, gfxTextRun* aTextRun,
   gfxTextRun::Metrics metrics =
       aTextRun->MeasureText(gfxFont::LOOSE_INK_EXTENTS, nullptr);
 
+  auto convertIfVerticalRL = [&](gfxFloat dominantBaseline) {
+    return writingMode.IsVerticalRL()
+               ? metrics.mAscent + metrics.mDescent - dominantBaseline
+               : dominantBaseline;
+  };
+
   switch (aDominantBaseline) {
     case StyleDominantBaseline::Hanging:
-      return metrics.mAscent * 0.2;
+      return convertIfVerticalRL(metrics.mAscent * 0.2);
     case StyleDominantBaseline::TextBeforeEdge:
-      return writingMode.IsVerticalRL() ? metrics.mAscent + metrics.mDescent
-                                        : 0;
+      return convertIfVerticalRL(0);
 
-    case StyleDominantBaseline::Auto:
     case StyleDominantBaseline::Alphabetic:
       return writingMode.IsVerticalRL()
-                 ? metrics.mAscent + metrics.mDescent -
-                       aFrame->GetLogicalBaseline(writingMode)
+                 ? metrics.mAscent * 0.5
                  : aFrame->GetLogicalBaseline(writingMode);
 
+    case StyleDominantBaseline::Auto:
+      return convertIfVerticalRL(aFrame->GetLogicalBaseline(writingMode));
+
     case StyleDominantBaseline::Middle:
-      return aFrame->GetLogicalBaseline(writingMode) -
-             SVGContentUtils::GetFontXHeight(aFrame) / 2.0 *
-                 AppUnitsPerCSSPixel() * aFontSizeScaleFactor;
+      return convertIfVerticalRL(aFrame->GetLogicalBaseline(writingMode) -
+                                 SVGContentUtils::GetFontXHeight(aFrame) / 2.0 *
+                                     AppUnitsPerCSSPixel() *
+                                     aFontSizeScaleFactor);
 
     case StyleDominantBaseline::TextAfterEdge:
     case StyleDominantBaseline::Ideographic:
@@ -310,11 +317,11 @@ static nscoord GetBaselinePosition(nsTextFrame* aFrame, gfxTextRun* aTextRun,
     case StyleDominantBaseline::Central:
       return (metrics.mAscent + metrics.mDescent) / 2.0;
     case StyleDominantBaseline::Mathematical:
-      return metrics.mAscent / 2.0;
+      return convertIfVerticalRL(metrics.mAscent / 2.0);
   }
 
   MOZ_ASSERT_UNREACHABLE("unexpected dominant-baseline value");
-  return aFrame->GetLogicalBaseline(writingMode);
+  return convertIfVerticalRL(aFrame->GetLogicalBaseline(writingMode));
 }
 
 /**