FrameSelection::updateApperance for caret should not cause layout.

Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 254 matching lines @@
 
     VisibleSelection oldSelection = m_selection;
 
     m_selection = s;
     setCaretRectNeedsUpdate();
 
     if (!s.isNone() && !(options & DoNotSetFocus))
         setFocusedNodeIfNeeded();
 
     if (!(options & DoNotUpdateAppearance)) {
-        m_frame->document()->updateLayoutIgnorePendingStylesheets();
-
         // Hits in compositing/overflow/do-not-paint-outline-into-composited-scrolling-contents.html
         DisableCompositingQueryAsserts disabler;
         updateAppearance();

[esprehn, 2014/08/05 01:00:02]

updateAppearance creates a VisiblePosition which is going to cause a layout
inside its constructor. I don't think this patch does anything.

[yoichio, 2014/08/05 05:56:38]

Yes. We call layout to get right caret position in content editable elements 
and decide if we repaint caret to another position.
However, if we call updateAppearance more than once before paint, current
implementation can call layout each time before painting.
This causes bad performance.
In this CL, I want to call at most one layout for textarea for caret painting
regardless of updateAppearance calls.

     }
 
     // Always clear the x position used for vertical arrow navigation.
     // It will be restored by the vertical arrow navigation code if necessary.
     m_xPosForVerticalArrowNavigation = NoXPosForVerticalArrowNavigation();
     selectFrameElementInParentIfFullySelected();
     notifyRendererOfSelectionChange(userTriggered);
     m_frame->editor().respondToChangedSelection(oldSelection, options);
     if (userTriggered == UserTriggered) {
         ScrollAlignment alignment;
@@ skipping 933 matching lines @@
 static bool isNonOrphanedCaret(const VisibleSelection& selection)
 {
     return selection.isCaret() && !selection.start().isOrphan() && !selection.end().isOrphan();
 }
 
 static bool isTextFormControl(const VisibleSelection& selection)
 {
     return enclosingTextFormControl(selection.start());
 }
 
-LayoutRect FrameSelection::localCaretRect()
+void FrameSelection::updateLocalCaretRect()
 {
     if (shouldUpdateCaretRect()) {
-        if (!isNonOrphanedCaret(m_selection))
+        if (!isNonOrphanedCaret(m_selection)) {
             clearCaretRect();
-        else if (isTextFormControl(m_selection))
+        } else if (isTextFormControl(m_selection)) {
+            m_frame->document()->updateLayoutIgnorePendingStylesheets();
             m_absCaretBoundsDirty |= updateCaretRect(m_frame->document(), PositionWithAffinity(m_selection.start().isCandidate() ? m_selection.start() : Position(), m_selection.affinity()));
-        else
+        } else {
             m_absCaretBoundsDirty |= updateCaretRect(m_frame->document(), VisiblePosition(m_selection.start(), m_selection.affinity()));
+        }
     }
-
-    return localCaretRectWithoutUpdate();
 }
 
 IntRect FrameSelection::absoluteCaretBounds()
 {
     recomputeCaretRect();
     return m_absCaretBounds;
 }
 
 bool FrameSelection::recomputeCaretRect()
 {
     if (!shouldUpdateCaretRect())
         return false;
 
     if (!m_frame || !m_frame->document()->view())
         return false;
 
     LayoutRect oldRect = localCaretRectWithoutUpdate();
-    LayoutRect newRect = localCaretRect();
+    updateLocalCaretRect();
+    LayoutRect newRect = localCaretRectWithoutUpdate();
     if (oldRect == newRect && !m_absCaretBoundsDirty)
         return false;
 
     IntRect oldAbsCaretBounds = m_absCaretBounds;
     m_absCaretBounds = absoluteBoundsForLocalRect(m_selection.start().deprecatedNode(), localCaretRectWithoutUpdate());
     m_absCaretBoundsDirty = false;
 
     if (oldAbsCaretBounds == m_absCaretBounds)
         return false;
 
@@ skipping 12 matching lines @@
 void FrameSelection::invalidateCaretRect()
 {
     if (!isCaret())
         return;
 
     CaretBase::invalidateCaretRect(m_selection.start().deprecatedNode(), recomputeCaretRect());
 }
 
 void FrameSelection::paintCaret(GraphicsContext* context, const LayoutPoint& paintOffset, const LayoutRect& clipRect)
 {
-    if (m_selection.isCaret() && m_caretPaint)
+    if (m_selection.isCaret() && m_caretPaint) {
+        updateLocalCaretRect();

[esprehn, 2014/08/05 01:00:02]

Calling updateLayoutIgnorePendingStylesheets from inside paint() is not correct,
this should both crash and would have caused security bugs.

[yoichio, 2014/08/05 05:56:38]

OK. How about calling updateLocalCaretRect in WebViewImpl::beginFrame?
WebViewImpl::beginFrame is called before paint and calls callback functions
inserted by Document::requestAnimationFrame for example.

         CaretBase::paintCaret(m_selection.start().deprecatedNode(), context, paintOffset, clipRect);
+    }
 }
 
 bool FrameSelection::contains(const LayoutPoint& point)
 {
     Document* document = m_frame->document();
 
     // Treat a collapsed selection like no selection.
     if (!isRange())
         return false;
     if (!document->renderView())
@@ skipping 228 matching lines @@
     return m_focused && m_frame->page() && m_frame->page()->focusController().isActive();
 }
 
 inline static bool shouldStopBlinkingDueToTypingCommand(LocalFrame* frame)
 {
     return frame->editor().lastEditCommand() && frame->editor().lastEditCommand()->shouldStopCaretBlinking();
 }
 
 void FrameSelection::updateAppearance()
 {
+    bool isTextForm = isTextFormControl(m_selection);

[esprehn, 2014/08/05 01:00:02]

I don't think we want to special case stuff like this.

[yoichio, 2014/08/05 05:56:38]

Actually, this CL is for improvement benchmark score using textarea:
http://browserbench.org/Speedometer/
Thus I want to create a fast path for HTMLTextFormControlElement.

     // Paint a block cursor instead of a caret in overtype mode unless the caret is at the end of a line (in this case
     // the FrameSelection will paint a blinking caret as usual).
     VisiblePosition forwardPosition;
     if (m_shouldShowBlockCursor && m_selection.isCaret()) {
         forwardPosition = modifyExtendingForward(CharacterGranularity);
         m_caretPaint = forwardPosition.isNull();
     }
 
-    bool caretRectChangedOrCleared = recomputeCaretRect();
+    bool caretRectChangedOrCleared = isTextForm || recomputeCaretRect();
     bool shouldBlink = shouldBlinkCaret() && forwardPosition.isNull();
 
     // If the caret moved, stop the blink timer so we can restart with a
     // black caret in the new location.
     if (caretRectChangedOrCleared || !shouldBlink || shouldStopBlinkingDueToTypingCommand(m_frame)) {
         m_caretBlinkTimer.stop();
         if (!shouldBlink && m_caretPaint) {
             m_caretPaint = false;
             invalidateCaretRect();
         }
@@ skipping 10 matching lines @@
             invalidateCaretRect();
         }
     }
 
     RenderView* view = m_frame->contentRenderer();
     if (!view)
         return;
 
     // Construct a new VisibleSolution, since m_selection is not necessarily valid, and the following steps
     // assume a valid selection. See <https://bugs.webkit.org/show_bug.cgi?id=69563> and <rdar://problem/10232866>.
-    VisibleSelection selection(m_selection.visibleStart(), forwardPosition.isNotNull() ? forwardPosition : m_selection.visibleEnd());
+    VisibleSelection selection;
+    if (isTextForm)
+        selection.setWithoutValidation(m_selection.start(), forwardPosition.isNotNull() ? forwardPosition.deepEquivalent() : m_selection.end());
+    else
+        selection = VisibleSelection(m_selection.visibleStart(), forwardPosition.isNotNull() ? forwardPosition : m_selection.visibleEnd());
 
     if (!selection.isRange()) {
         view->clearSelection();
         return;
     }
 
     // Use the rightmost candidate for the start of the selection, and the leftmost candidate for the end of the selection.
     // Example: foo <a>bar</a>.  Imagine that a line wrap occurs after 'foo', and that 'bar' is selected.   If we pass [foo, 3]
     // as the start of the selection, the selection painting code will think that content on the line containing 'foo' is selected
     // and will fill the gap before 'bar'.
@@ skipping 55 matching lines @@
     ASSERT(caretIsVisible());
     ASSERT(isCaret());
     if (isCaretBlinkingSuspended() && m_caretPaint)
         return;
     m_caretPaint = !m_caretPaint;
     invalidateCaretRect();
 }
 
 void FrameSelection::notifyRendererOfSelectionChange(EUserTriggered userTriggered)
 {
-    m_frame->document()->updateRenderTreeIfNeeded();
-
     if (HTMLTextFormControlElement* textControl = enclosingTextFormControl(start()))
         textControl->selectionChanged(userTriggered == UserTriggered);
 }
 
 // Helper function that tells whether a particular node is an element that has an entire
 // LocalFrame and FrameView, a <frame>, <iframe>, or <object>.
 static bool isFrameElement(const Node* n)
 {
     if (!n)
         return false;
@@ skipping 255 matching lines @@
     sel.showTreeForThis();
 }
 
 void showTree(const blink::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
 }
 
 #endif