Paint state transition for overlay 9 patch scrollbars

ui/native_theme/native_theme_aura.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/native_theme/native_theme_aura.h"
 
 #include <limits>
 
 #include "base/logging.h"
 #include "grit/ui_resources.h"
@@ skipping 190 matching lines @@
   if (part == NativeTheme::kScrollbarVerticalThumb)
     thumb_rect.Inset(2, extra_padding, 2, extra_padding);
   else
     thumb_rect.Inset(extra_padding, 2, extra_padding, 2);
   PaintPainter(GetOrCreatePainter(
                    kScrollbarThumbImages, state, scrollbar_thumb_painters_),
                sk_canvas,
                thumb_rect);
 }
 
+void NativeThemeAura::PaintScrollbarThumbStateTransition(
+    SkCanvas* canvas,
+    State startState,
+    State endState,
+    double progress,
+    const gfx::Rect& rect) const {
+  // Only Overlay scrollbars should have state transition animation.
+  DCHECK(IsOverlayScrollbarEnabled());
+  if (!scrollbar_overlay_thumb_painter_) {
+    scrollbar_overlay_thumb_painter_ =
+        CreateDualPainter(kScrollbarOverlayThumbFillImages,
+                          kScrollbarOverlayThumbFillAlphas,
+                          kScrollbarOverlayThumbStrokeImages,
+                          kScrollbarOverlayThumbStrokeAlphas);
+  }
+
+  PaintDualPainterTransition(scrollbar_overlay_thumb_painter_.get(),
+                             canvas,
+                             rect,
+                             startState,
+                             endState,
+                             progress);
+}
+
 void NativeThemeAura::PaintScrollbarCorner(SkCanvas* canvas,
                                            State state,
                                            const gfx::Rect& rect) const {
   // Overlay Scrollbar should never paint a scrollbar corner.
   DCHECK(!IsOverlayScrollbarEnabled());
   SkPaint paint;
   paint.setColor(SkColorSetRGB(0xF1, 0xF1, 0xF1));
   paint.setStyle(SkPaint::kFill_Style);
   paint.setXfermodeMode(SkXfermode::kSrc_Mode);
   canvas->drawIRect(RectToSkIRect(rect), paint);
@@ skipping 41 matching lines @@
     const gfx::Rect& rect,
     State state) const {
   DCHECK(dual_painter);
   scoped_ptr<gfx::Canvas> canvas(CreateCanvas(sk_canvas));
   dual_painter->fill_painter->Paint(
       canvas.get(), rect, dual_painter->fill_alphas[state]);
   dual_painter->stroke_painter->Paint(
       canvas.get(), rect, dual_painter->stroke_alphas[state]);
 }
 
+void NativeThemeAura::PaintDualPainterTransition(
+    NativeThemeAura::DualPainter* dual_painter,
+    SkCanvas* sk_canvas,
+    const gfx::Rect& rect,
+    State startState,
+    State endState,
+    double progress) const {
+  DCHECK(dual_painter);
+  scoped_ptr<gfx::Canvas> canvas(CreateCanvas(sk_canvas));
+  uint8 fill_alpha = dual_painter->fill_alphas[startState] +
+                     (dual_painter->fill_alphas[endState] -
+                      dual_painter->fill_alphas[startState]) *
+                         progress;
+  uint8 stroke_alpha = dual_painter->stroke_alphas[startState] +
+                       (dual_painter->stroke_alphas[endState] -
+                        dual_painter->stroke_alphas[startState]) *
+                           progress;
+
+  dual_painter->fill_painter->Paint(canvas.get(), rect, fill_alpha);
+  dual_painter->stroke_painter->Paint(canvas.get(), rect, stroke_alpha);
+}
+
 NativeThemeAura::DualPainter::DualPainter(
     scoped_ptr<NineImagePainter> fill_painter,
     const uint8 fill_alphas[kMaxState],
     scoped_ptr<NineImagePainter> stroke_painter,
     const uint8 stroke_alphas[kMaxState])
     : fill_painter(fill_painter.Pass()),
       fill_alphas(fill_alphas),
       stroke_painter(stroke_painter.Pass()),
       stroke_alphas(stroke_alphas) {}
 
 NativeThemeAura::DualPainter::~DualPainter() {}
 
 }  // namespace ui