Introduce support for text-decoration-skip: ink

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/TextPainter.h"
 
 #include "core/CSSPropertyNames.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutObject.h"
 #include "core/layout/LayoutTextCombine.h"
@@ skipping 234 matching lines @@
     textRunPaintInfo.cachedTextBlob = cachedTextBlob;
     paintInternalRun<Step>(textRunPaintInfo, startOffset, endOffset);
   } else {
     if (endOffset > 0)
       paintInternalRun<Step>(textRunPaintInfo, 0, endOffset);
     if (startOffset < truncationPoint)
       paintInternalRun<Step>(textRunPaintInfo, startOffset, truncationPoint);
   }
 }
 
+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);
   FloatPoint emphasisMarkTextOrigin(m_textBounds.x().toFloat(),
                                     m_textBounds.y().toFloat() +
                                         m_font.getFontMetrics().ascent() +
                                         m_emphasisMarkOffset);
   TextRunPaintInfo textRunPaintInfo(placeholderTextRun);
   textRunPaintInfo.bounds = FloatRect(m_textBounds);
   m_graphicsContext.concatCTM(rotation(m_textBounds, Clockwise));
   m_graphicsContext.drawEmphasisMarks(m_combinedText->originalFont(),
                                       textRunPaintInfo, m_emphasisMark,
                                       emphasisMarkTextOrigin);
   m_graphicsContext.concatCTM(rotation(m_textBounds, Counterclockwise));
 }
 
 }  // namespace blink