Introduce support for text-decoration-skip: ink

third_party/WebKit/Source/core/paint/TextPainter.cpp

Index: third_party/WebKit/Source/core/paint/TextPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/TextPainter.cpp b/third_party/WebKit/Source/core/paint/TextPainter.cpp
index 274b395f30f443bc2f389e92c5abbd614ea0a6f6..77d78da1d921a6c2d66b2262c230c1860912371c 100644
--- a/third_party/WebKit/Source/core/paint/TextPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/TextPainter.cpp
@@ -252,6 +252,35 @@ void TextPainter::paintInternal(unsigned startOffset,
   }
 }
 
+void TextPainter::clipDecorationsStripe(float upper,
+                                        float stripeWidth,
+                                        float dilation) {
+  TextRunPaintInfo textRunPaintInfo(m_run);
+
+  if (!m_run.length())
+    return;
+
+  SkScalar lineBounds[] = {upper, upper + stripeWidth};
+  const int numIntervals = m_graphicsContext.getTextIntercepts(
+      m_font, textRunPaintInfo, lineBounds, nullptr);
+  SkScalar intervals[numIntervals];
+  m_graphicsContext.getTextIntercepts(m_font, textRunPaintInfo, lineBounds,
+                                      intervals);
+
+  for (int i = 0; i < numIntervals; i += 2) {

[eae, 2016/10/13 18:18:54]

Do we want to assert that the number of intervals is even?

[drott, 2016/10/13 18:39:29]

Makes sense, adding an assert.

+    FloatPoint clipOrigin(m_textOrigin);
+    FloatRect clipRect(clipOrigin + FloatPoint(intervals[i], upper),
+                       FloatSize(intervals[i + 1] - intervals[i], stripeWidth));
+    clipRect.inflateX(dilation);
+    clipRect = enclosingIntRect(clipRect);
+    m_graphicsContext.setFillColor(Color(127, 0, 0, 127));

[eae, 2016/10/13 18:18:54]

Hard coded color? This is temporary, right?

[drott, 2016/10/13 18:39:29]

Yep, the whole paintRect can go, and no color setting is needed, this was debug
code.

+    FloatRect paintClipRect(clipRect);
+    paintClipRect.inflateX(clipRect.width() * -0.25);

[eae, 2016/10/13 18:18:54]

Please add a comment explaining the 0.25 value.

+    // m_graphicsContext.fillRect(paintClipRect);
+    m_graphicsContext.clipOut(clipRect);
+  }
+}
+
 void TextPainter::paintEmphasisMarkForCombinedText() {
   ASSERT(m_combinedText);
   TextRun placeholderTextRun(&ideographicFullStopCharacter, 1);