Separate advance from offset in GlypBuffer

Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp

Index: Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp
diff --git a/Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp b/Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp
index 2fd38bf7a7bd3210200522549f47e7364be4ac10..c776c1f033d3bdb4a56213c842bcca9997c3b10d 100644
--- a/Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp
+++ b/Source/platform/fonts/harfbuzz/FontHarfBuzz.cpp
@@ -157,7 +157,7 @@ void Font::drawGlyphs(GraphicsContext* gc, const SimpleFontData* font,
                 pos[i].set(
                     x + SkIntToScalar(lroundf(translations[i].x())),
                     y + -SkIntToScalar(-lroundf(currentWidth - translations[i].y())));
-                currentWidth += glyphBuffer.advanceAt(from + glyphIndex).width();
+                currentWidth += glyphBuffer.advanceAt(from + glyphIndex);
             }
             horizontalOffset += currentWidth;
             paintGlyphs(gc, font, glyphs, chunkLength, pos, textRect);
@@ -167,35 +167,35 @@ void Font::drawGlyphs(GraphicsContext* gc, const SimpleFontData* font,
         return;
     }
 
-    if (!glyphBuffer.hasVerticalAdvances()) {
+    if (!glyphBuffer.hasOffsets()) {
         SkAutoSTMalloc<64, SkScalar> storage(numGlyphs);
         SkScalar* xpos = storage.get();
-        const FloatSize* adv = glyphBuffer.advances(from);
+        const float* adv = glyphBuffer.advances(from);
         for (unsigned i = 0; i < numGlyphs; i++) {
             xpos[i] = x;
-            x += SkFloatToScalar(adv[i].width());
+            x += SkFloatToScalar(adv[i]);
         }
         const Glyph* glyphs = glyphBuffer.glyphs(from);
         paintGlyphsHorizontal(gc, font, glyphs, numGlyphs, xpos, SkFloatToScalar(y), textRect);
         return;
     }
 
-    // FIXME: text rendering speed:
-    // Android has code in their WebCore fork to special case when the
-    // GlyphBuffer has no advances other than the defaults. In that case the
-    // text drawing can proceed faster. However, it's unclear when those
-    // patches may be upstreamed to WebKit so we always use the slower path
-    // here.
+    ASSERT(glyphBuffer.hasOffsets());
+    const GlyphBufferWithOffsets& glyphBufferWithOffsets =
+        static_cast<const GlyphBufferWithOffsets&>(glyphBuffer);
     SkAutoSTMalloc<32, SkPoint> storage(numGlyphs);
     SkPoint* pos = storage.get();
-    const FloatSize* adv = glyphBuffer.advances(from);
+    const FloatSize* offsets = glyphBufferWithOffsets.offsets(from);
+    const float* advances = glyphBufferWithOffsets.advances(from);
+    SkScalar advanceSoFar = SkFloatToScalar(0);
     for (unsigned i = 0; i < numGlyphs; i++) {
-        pos[i].set(x, y);
-        x += SkFloatToScalar(adv[i].width());
-        y += SkFloatToScalar(adv[i].height());
+        pos[i].set(
+            x + SkFloatToScalar(offsets[i].width()) + advanceSoFar,
+            y + SkFloatToScalar(offsets[i].height()));
+        advanceSoFar += SkFloatToScalar(advances[i]);
     }
 
-    const Glyph* glyphs = glyphBuffer.glyphs(from);
+    const Glyph* glyphs = glyphBufferWithOffsets.glyphs(from);
     paintGlyphs(gc, font, glyphs, numGlyphs, pos, textRect);
 }
 
@@ -231,13 +231,12 @@ float Font::drawComplexText(GraphicsContext* gc, const TextRunPaintInfo& runInfo
     if (!fill && !stroke)
         return 0;
 
-    GlyphBuffer glyphBuffer;
+    GlyphBufferWithOffsets glyphBuffer;
     HarfBuzzShaper shaper(this, runInfo.run);
     shaper.setDrawRange(runInfo.from, runInfo.to);
     if (!shaper.shape(&glyphBuffer) || glyphBuffer.isEmpty())
         return 0;
-    FloatPoint adjustedPoint = shaper.adjustStartPoint(point);
-    return drawGlyphBuffer(gc, runInfo, glyphBuffer, adjustedPoint);
+    return drawGlyphBuffer(gc, runInfo, glyphBuffer, point);
 }
 
 void Font::drawEmphasisMarksForComplexText(GraphicsContext* context, const TextRunPaintInfo& runInfo, const AtomicString& mark, const FloatPoint& point) const
@@ -302,7 +301,6 @@ PassTextBlobPtr Font::buildTextBlob(const GlyphBuffer& glyphBuffer, float initia
 
     // FIXME: Except for setupPaint, this is not specific to FontHarfBuzz.
     // FIXME: Also implement the more general full-positioning path.
-    ASSERT(!glyphBuffer.hasVerticalAdvances());

[jbroman, 2014/09/26 13:02:11]

Mind putting the equivalent assertion back here?

ASSERT(!glyphBuffer.hasOffsets());

This path doesn't currently handle the complex case where there are offsets (and
it would merrily position such runs horizontally, which is wrong). It shouldn't
be reachable in such cases, but it would be nice to keep asserting that.

 
     SkTextBlobBuilder builder;
     SkScalar x = SkFloatToScalar(initialAdvance);
@@ -340,10 +338,10 @@ PassTextBlobPtr Font::buildTextBlob(const GlyphBuffer& glyphBuffer, float initia
         const uint16_t* glyphs = glyphBuffer.glyphs(start);
         std::copy(glyphs, glyphs + count, buffer.glyphs);
 
-        const FloatSize* advances = glyphBuffer.advances(start);
+        const float* advances = glyphBuffer.advances(start);
         for (unsigned j = 0; j < count; j++) {
             buffer.pos[j] = x;
-            x += SkFloatToScalar(advances[j].width());
+            x += SkFloatToScalar(advances[j]);
         }
     }