Use DrawingRecorder::canUseCachedDrawing

Source/core/paint/BlockPainter.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 "config.h"
 #include "core/paint/BlockPainter.h"
 
 #include "core/editing/Caret.h"
 #include "core/editing/FrameSelection.h"
 #include "core/frame/LocalFrame.h"
@@ skipping 69 matching lines @@
     // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
     // z-index. We paint after we painted the background/border, so that the scrollbars will
     // sit above the background/border.
     paintOverflowControlsIfNeeded(localPaintInfo, adjustedPaintOffset);
 }
 
 void BlockPainter::paintOverflowControlsIfNeeded(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     PaintPhase phase = paintInfo.phase;
     if (m_renderBlock.hasOverflowClip() && m_renderBlock.style()->visibility() == VISIBLE && (phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) && paintInfo.shouldPaintWithinRoot(&m_renderBlock) && !paintInfo.paintRootBackgroundOnly()) {
-        RenderDrawingRecorder recorder(paintInfo.context, &m_renderBlock, paintInfo.phase, pixelSnappedIntRect(paintOffset, m_renderBlock.visualOverflowRect().size()));
-        ScrollableAreaPainter(*m_renderBlock.layer()->scrollableArea()).paintOverflowControls(paintInfo.context, roundedIntPoint(paintOffset), paintInfo.rect, false /* paintingOverlayControls */);
+        RenderDrawingRecorder recorder(paintInfo.context, m_renderBlock, paintInfo.phase, pixelSnappedIntRect(paintOffset, m_renderBlock.visualOverflowRect().size()));
+        if (!recorder.canUseCachedDrawing())
+            ScrollableAreaPainter(*m_renderBlock.layer()->scrollableArea()).paintOverflowControls(paintInfo.context, roundedIntPoint(paintOffset), paintInfo.rect, false /* paintingOverlayControls */);

[chrishtr, 2014/12/11 20:01:48]

Why are these safe? Unless we are very careful, we have to emit cached display
items in the correct order, or paint order might be messed up.

[Xianzhu, 2014/12/11 20:22:16]

I think we'll emit DrawingDisplayItems/CachedDisplayItems just like before in
the same order, while avoiding unnecessary paint operations on the context.

We have ensured that DrawingRecorders' life-times don't overlap, so we should
never emit DrawingDisplayItems/CachedDisplayItems within the block controlled by
'if (!recorder.canUseCachedDrawing())'.

[chrishtr, 2014/12/12 00:18:08]

Oh right, it's within a block that has a DrawingRecorder. Good point. Nice.

     }
 }
 
 void BlockPainter::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     for (RenderBox* child = m_renderBlock.firstChildBox(); child; child = child->nextSiblingBox())
         paintChild(child, paintInfo, paintOffset);
 }
 
 void BlockPainter::paintChild(RenderBox* child, const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
@@ skipping 69 matching lines @@
     }
 
     if ((paintPhase == PaintPhaseBlockBackground || paintPhase == PaintPhaseChildBlockBackground) && m_renderBlock.style()->visibility() == VISIBLE) {
         if (m_renderBlock.hasBoxDecorationBackground())
             m_renderBlock.paintBoxDecorationBackground(paintInfo, paintOffset);
         if (m_renderBlock.hasColumns() && !paintInfo.paintRootBackgroundOnly())
             paintColumnRules(paintInfo, scrolledOffset);
     }
 
     if (paintPhase == PaintPhaseMask && m_renderBlock.style()->visibility() == VISIBLE) {
-        RenderDrawingRecorder recorder(paintInfo.context, &m_renderBlock, paintPhase, bounds);
-        m_renderBlock.paintMask(paintInfo, paintOffset);
+        RenderDrawingRecorder recorder(paintInfo.context, m_renderBlock, paintPhase, bounds);
+        if (!recorder.canUseCachedDrawing())
+            m_renderBlock.paintMask(paintInfo, paintOffset);
         return;
     }
 
     if (paintPhase == PaintPhaseClippingMask && m_renderBlock.style()->visibility() == VISIBLE) {
-        RenderDrawingRecorder recorder(paintInfo.context, &m_renderBlock, paintPhase, bounds);
-        m_renderBlock.paintClippingMask(paintInfo, paintOffset);
+        RenderDrawingRecorder recorder(paintInfo.context, m_renderBlock, paintPhase, bounds);
+        if (!recorder.canUseCachedDrawing())
+            m_renderBlock.paintClippingMask(paintInfo, paintOffset);
         return;
     }
 
     // We're done. We don't bother painting any children.
     if (paintPhase == PaintPhaseBlockBackground || paintInfo.paintRootBackgroundOnly())
         return;
 
     if (paintPhase != PaintPhaseSelfOutline) {
         if (m_renderBlock.hasColumns())
             paintColumnContents(paintInfo, scrolledOffset);
@@ skipping 19 matching lines @@
         if (!m_renderBlock.style()->outlineStyleIsAuto() || !m_renderBlock.isAnonymousBlockContinuation())
             ObjectPainter(m_renderBlock).paintOutline(paintInfo, LayoutRect(paintOffset, m_renderBlock.size()));
     }
 
     if (paintPhase == PaintPhaseOutline || paintPhase == PaintPhaseChildOutlines)
         paintContinuationOutlines(paintInfo, paintOffset);
 
     // If the caret's node's render object's containing block is this block, and the paint action is PaintPhaseForeground,
     // then paint the caret.
     if (paintPhase == PaintPhaseForeground) {
-        RenderDrawingRecorder recorder(paintInfo.context, &m_renderBlock, paintPhase, bounds);
-        paintCarets(paintInfo, paintOffset);
+        RenderDrawingRecorder recorder(paintInfo.context, m_renderBlock, paintPhase, bounds);
+        if (!recorder.canUseCachedDrawing())
+            paintCarets(paintInfo, paintOffset);
     }
 }
 
 static inline bool caretBrowsingEnabled(const Frame* frame)
 {
     Settings* settings = frame->settings();
     return settings && settings->caretBrowsingEnabled();
 }
 
 static inline bool hasCursorCaret(const FrameSelection& selection, const RenderBlock* block, bool caretBrowsing)
@@ skipping 245 matching lines @@
         RenderBlock* block = flow->containingBlock();
         for ( ; block && block != &m_renderBlock; block = block->containingBlock())
             accumulatedPaintOffset.moveBy(block->location());
         ASSERT(block);
         InlinePainter(*flow).paintOutline(info, accumulatedPaintOffset);
     }
 }
 
 
 } // namespace blink