ui: Cache the output of View::OnPaint when the View isn't invalid.

ui/views/view.cc

 // Copyright (c) 2012 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.
 
 #define _USE_MATH_DEFINES // For VC++ to get M_PI. This has to be first.
 
 #include "ui/views/view.h"
 
 #include <algorithm>
 #include <cmath>
@@ skipping 730 matching lines @@
   gfx::Vector2d offset_to_parent;
   if (!layer()) {
     // If the View has a layer() then it is a paint root. Otherwise, we need to
     // add the offset from the parent into the total offset from the paint root.
     DCHECK_IMPLIES(!parent(), bounds().origin() == gfx::Point());
     offset_to_parent = GetMirroredPosition().OffsetFromOrigin();
   }
   ui::PaintContext context =
       parent_context.CloneWithPaintOffset(offset_to_parent);
 
-  if (context.CanCheckInvalidated()) {
+  bool is_invalidated = true;
+  if (context.CanCheckInvalid()) {
 #if DCHECK_IS_ON()
     gfx::Vector2d offset;
     context.Visited(this);
     View* view = this;
     while (view->parent() && !view->layer()) {
       DCHECK(view->GetTransform().IsIdentity());
       offset += view->GetMirroredPosition().OffsetFromOrigin();
       view = view->parent();
     }
     // The offset in the PaintContext should be the offset up to the paint root,
     // which we compute and verify here.
     DCHECK_EQ(context.PaintOffset().x(), offset.x());
     DCHECK_EQ(context.PaintOffset().y(), offset.y());
     // The above loop will stop when |view| is the paint root, which should be
     // the root of the current paint walk, as verified by storing the root in
     // the PaintContext.
     DCHECK_EQ(context.RootVisited(), view);
 #endif
 
     // If the View wasn't invalidated, don't waste time painting it, the output
     // would be culled.
-    if (!context.IsRectInvalidated(GetLocalBounds()))
-      return;
+    is_invalidated = context.IsRectInvalid(GetLocalBounds());
   }
 
+  if (!is_invalidated && context.ShouldEarlyOutOfPaintingWhenValid())
+    return;
+
   TRACE_EVENT1("views", "View::Paint", "class", GetClassName());
 
   // If the view is backed by a layer, it should paint with itself as the origin
   // rather than relative to its parent.
   scoped_ptr<ui::ClipTransformRecorder> clip_transform_recorder;
   if (!layer()) {
     clip_transform_recorder.reset(new ui::ClipTransformRecorder(context));
 
     // Set the clip rect to the bounds of this View. Note that the X (or left)
     // position we pass to ClipRect takes into consideration whether or not the
     // View uses a right-to-left layout so that we paint the View in its
     // mirrored position if need be.
     gfx::Rect clip_rect_in_parent = bounds();
     clip_rect_in_parent.Inset(clip_insets_);
     if (parent_)
       clip_rect_in_parent.set_x(
           parent_->GetMirroredXForRect(clip_rect_in_parent));
     clip_transform_recorder->ClipRect(clip_rect_in_parent);
 
     // Translate the graphics such that 0,0 corresponds to where
     // this View is located relative to its parent.
     gfx::Transform transform_from_parent;
     gfx::Vector2d offset_from_parent = GetMirroredPosition().OffsetFromOrigin();
     transform_from_parent.Translate(offset_from_parent.x(),
                                     offset_from_parent.y());
     transform_from_parent.PreconcatTransform(GetTransform());
     clip_transform_recorder->Transform(transform_from_parent);
   }
 
-  {
-    ui::PaintRecorder recorder(context);
+  if (is_invalidated || !paint_cache_.UseCache(context)) {
+    ui::PaintRecorder recorder(context, &paint_cache_);
     gfx::Canvas* canvas = recorder.canvas();
     gfx::ScopedCanvas scoped_canvas(canvas);
 
     // If the View we are about to paint requested the canvas to be flipped, we
     // should change the transform appropriately.
     // The canvas mirroring is undone once the View is done painting so that we
     // don't pass the canvas with the mirrored transform to Views that didn't
     // request the canvas to be flipped.
     if (FlipCanvasOnPaintForRTLUI()) {
       canvas->Translate(gfx::Vector2d(width(), 0));
@@ skipping 1551 matching lines @@
   // Message the RootView to do the drag and drop. That way if we're removed
   // the RootView can detect it and avoid calling us back.
   gfx::Point widget_location(event.location());
   ConvertPointToWidget(this, &widget_location);
   widget->RunShellDrag(this, data, widget_location, drag_operations, source);
   // WARNING: we may have been deleted.
   return true;
 }
 
 }  // namespace views