TextBlob: Start caching a text blob per InlineTextBox.

Source/core/rendering/TextPainter.cpp

Index: Source/core/rendering/TextPainter.cpp
diff --git a/Source/core/rendering/TextPainter.cpp b/Source/core/rendering/TextPainter.cpp
index 724bfd40e08cfb73a176ae714b49bde12b390877..43f4a1360668e3a927db20832eabc82b43737e01 100644
--- a/Source/core/rendering/TextPainter.cpp
+++ b/Source/core/rendering/TextPainter.cpp
@@ -47,11 +47,11 @@ void TextPainter::setEmphasisMark(const AtomicString& emphasisMark, TextEmphasis
     }
 }
 
-void TextPainter::paint(int startOffset, int endOffset, int length, const Style& textStyle)
+void TextPainter::paint(int startOffset, int endOffset, int length, const Style& textStyle, TextBlobPtr* textBlobCache)
 {
     GraphicsContextStateSaver stateSaver(*m_graphicsContext, false);
     updateGraphicsContext(textStyle, stateSaver);
-    paintInternal<PaintText>(startOffset, endOffset, length);
+    paintInternal<PaintText>(startOffset, endOffset, length, textBlobCache);
 
     if (!m_emphasisMark.isEmpty()) {
         if (textStyle.emphasisMarkColor != textStyle.fillColor)
@@ -96,25 +96,52 @@ void TextPainter::updateGraphicsContext(GraphicsContext* context, const Style& t
     }
 }
 
+static bool graphicsContextAllowsTextBlobs(GraphicsContext* context)
+{
+    // Text blobs affect the shader coordinate space.
+    // FIXME: Fix this, most likely in Skia.
+    return !context->strokeGradient() && !context->strokePattern() && !context->fillGradient() && !context->fillPattern();
+}
+
 template <TextPainter::PaintInternalStep step>
-void TextPainter::paintInternalRun(TextRunPaintInfo& textRunPaintInfo, int from, int to)
+void TextPainter::paintInternalRun(TextRunPaintInfo& textRunPaintInfo, int from, int to, TextBlobPtr* textBlobCache)
 {
     textRunPaintInfo.from = from;
     textRunPaintInfo.to = to;
-    if (step == PaintEmphasisMark)
+
+    if (step == PaintEmphasisMark) {
         m_graphicsContext->drawEmphasisMarks(m_font, textRunPaintInfo, m_emphasisMark, m_textOrigin + IntSize(0, m_emphasisMarkOffset));
-    else
-        m_graphicsContext->drawText(m_font, textRunPaintInfo, m_textOrigin);
+        return;
+    }
 
+    ASSERT(step == PaintText);
+
+    // We transfer the original ref back and forth with the cache to avoid
+    // thrashing the ref count. Skia will take a ref, so we can't just ref
+    // the blob here and then pass that reference to Skia.

[f(malita), 2014/09/12 13:21:23]

We may be able to attain the same using something like

    TextBlobPtr throwAwayBlob;
    if (!textBlobCache) {
        textBlobCache = &throwAwayBlob;
    }

    if (!*textBlobCache && canUseTextBlobs)
        *textBlobCache = m_font.buildTextBlob(textRunPaintInfo, m_textOrigin,
            m_graphicsContext->couldUseLCDRenderedText());
    if (*textBlobCache && canUseTextBlobs) {
        m_font.drawTextBlob(m_graphicsContext, textBlobCache->get(),
m_textOrigin.data());
    } else {
        m_graphicsContext->drawText(m_font, textRunPaintInfo, m_textOrigin);
    }

WDYT?

[jbroman, 2014/09/13 00:06:42]

Yeah, okay. I'm not sure whether that's clearer or not, but I have no objection.

[jbroman, 2014/09/17 22:25:37]

I've changed to a variation on this theme.

+    TextBlobPtr textBlob = textBlobCache ? textBlobCache->release() : nullptr;
+    bool canUseTextBlobs = RuntimeEnabledFeatures::textBlobEnabled() && graphicsContextAllowsTextBlobs(m_graphicsContext);
+
+    if (!textBlob && canUseTextBlobs)
+        textBlob = m_font.buildTextBlob(textRunPaintInfo, m_textOrigin, m_graphicsContext->couldUseLCDRenderedText());
+
+    if (textBlob && canUseTextBlobs) {
+        m_font.drawTextBlob(m_graphicsContext, textBlob.get(), m_textOrigin.data());
+        if (textBlobCache)
+            *textBlobCache = textBlob.release();
+    } else {
+        m_graphicsContext->drawText(m_font, textRunPaintInfo, m_textOrigin);
+    }
 }
 
 template <TextPainter::PaintInternalStep Step>
-void TextPainter::paintInternal(int startOffset, int endOffset, int truncationPoint)
+void TextPainter::paintInternal(int startOffset, int endOffset, int truncationPoint, TextBlobPtr* textBlobCache)
 {
+    // FIXME: We should be able to use textBlobCache in more cases.
     TextRunPaintInfo textRunPaintInfo(m_run);
     textRunPaintInfo.bounds = m_textBounds;
     if (startOffset <= endOffset) {
-        paintInternalRun<Step>(textRunPaintInfo, startOffset, endOffset);
+        paintInternalRun<Step>(textRunPaintInfo, startOffset, endOffset, textBlobCache);
     } else {
         if (endOffset > 0)
             paintInternalRun<Step>(textRunPaintInfo, 0, endOffset);