Makes ImageView do a bit more checking before assuming images equal

ui/views/controls/image_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.
 
 #include "ui/views/controls/image_view.h"
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "ui/base/accessibility/accessible_view_state.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/insets.h"
 
 namespace views {
 
 ImageView::ImageView()
     : image_size_set_(false),
       horiz_alignment_(CENTER),
       vert_alignment_(CENTER),
-      interactive_(true) {
+      interactive_(true),
+      last_paint_scale_(0.f),
+      last_painted_image_(NULL) {
 }
 
 ImageView::~ImageView() {
 }
 
 void ImageView::SetImage(const gfx::ImageSkia& img) {
-  if (image_.BackedBySameObjectAs(img))
+  if (IsImageEqual(img))

[pkotwicz, 2013/11/15 20:57:09]

Can you please add a comment (in the code) as to why IsImageEqual() works the
way it does. (Which bug / suboptimality IsImageEqual() is working around)

[sky, 2013/11/15 22:19:13]

I placed the comment in IsImageEqual.

     return;
 
+  last_painted_image_ = NULL;
   gfx::Size pref_size(GetPreferredSize());
   image_ = img;
   if (pref_size != GetPreferredSize())
     PreferredSizeChanged();
   SchedulePaint();
 }
 
 void ImageView::SetImage(const gfx::ImageSkia* image_skia) {
   if (image_skia) {
     SetImage(*image_skia);
@@ skipping 35 matching lines @@
   if (image_size_set_) {
     gfx::Size image_size;
     GetImageSize(&image_size);
     image_size.Enlarge(insets.width(), insets.height());
     return image_size;
   }
   return gfx::Size(image_.width() + insets.width(),
                    image_.height() + insets.height());
 }
 
+bool ImageView::IsImageEqual(const gfx::ImageSkia& img) const {
+  return image_.BackedBySameObjectAs(img) &&
+      last_paint_scale_ != 0.0f &&
+      last_painted_image_ ==
+      img.GetRepresentation(last_paint_scale_).sk_bitmap().getPixels();
+}
+
 gfx::Point ImageView::ComputeImageOrigin(const gfx::Size& image_size) const {
   gfx::Insets insets = GetInsets();
 
   int x;
   // In order to properly handle alignment of images in RTL locales, we need
   // to flip the meaning of trailing and leading. For example, if the
   // horizontal alignment is set to trailing, then we'll use left alignment for
   // the image instead of right alignment if the UI layout is RTL.
   Alignment actual_horiz_alignment = horiz_alignment_;
   if (base::i18n::IsRTL() && (horiz_alignment_ != CENTER))
@@ skipping 12 matching lines @@
     case CENTER:   y = (height() - image_size.height()) / 2;             break;
     default:       NOTREACHED(); y = 0;                                  break;
   }
 
   return gfx::Point(x, y);
 }
 
 void ImageView::OnPaint(gfx::Canvas* canvas) {
   View::OnPaint(canvas);
 
+  last_paint_scale_ = canvas->image_scale();
+  last_painted_image_ = NULL;
+
   if (image_.isNull())
     return;
 
   gfx::Rect image_bounds(GetImageBounds());
   if (image_bounds.IsEmpty())
     return;
 
   if (image_bounds.size() != gfx::Size(image_.width(), image_.height())) {
     // Resize case
     SkPaint paint;
     paint.setFilterBitmap(true);
     canvas->DrawImageInt(image_, 0, 0, image_.width(), image_.height(),
         image_bounds.x(), image_bounds.y(), image_bounds.width(),
         image_bounds.height(), true, paint);
   } else {
     canvas->DrawImageInt(image_, image_bounds.x(), image_bounds.y());
   }
+  last_painted_image_ =
+      image_.GetRepresentation(last_paint_scale_).sk_bitmap().getPixels();
 }
 
 void ImageView::GetAccessibleState(ui::AccessibleViewState* state) {
   state->role = ui::AccessibilityTypes::ROLE_GRAPHIC;
   state->name = tooltip_text_;
 }
 
 void ImageView::SetHorizontalAlignment(Alignment ha) {
   if (ha != horiz_alignment_) {
     horiz_alignment_ = ha;
@@ skipping 30 matching lines @@
 
   *tooltip = GetTooltipText();
   return true;
 }
 
 bool ImageView::HitTestRect(const gfx::Rect& rect) const {
   return interactive_ ? View::HitTestRect(rect) : false;
 }
 
 }  // namespace views