gesture nav: Change how the shadows are painted.

Instead of creating a new parent aura::Window just for drawing the shadow,
and then duplicating that code for the overscroll window, create a single
layer for drawing the shadow (ShadowLayerDelegate) and use it for both
purposes. This cleans up a few pieces of code, and makes it possible to
use this same shadow code in a future CL.

BUG=226133, 196607
R=jam@chromium.org, sky@chromium.org

Review URL: https://codereview.chromium.org/14856007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@197986 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 107 insertions, 0 deletions

diff --git a/content/browser/web_contents/aura/shadow_layer_delegate.cc b/content/browser/web_contents/aura/shadow_layer_delegate.cc
new file mode 100644
index 0000000..8ff270b
--- /dev/null
+++ b/content/browser/web_contents/aura/shadow_layer_delegate.cc
@@ -0,0 +1,61 @@
+// Copyright (c) 2013 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 "content/browser/web_contents/aura/shadow_layer_delegate.h"
+
+#include "base/bind.h"
+#include "third_party/skia/include/effects/SkGradientShader.h"
+#include "ui/aura/window.h"
+#include "ui/compositor/layer.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/skia_util.h"
+
+namespace {
+
+const SkColor kShadowLightColor = SkColorSetARGB(0x0, 0, 0, 0);
+const SkColor kShadowDarkColor = SkColorSetARGB(0x70, 0, 0, 0);
+const int kShadowThick = 7;
+
+}  // namespace
+
+namespace content {
+
+ShadowLayerDelegate::ShadowLayerDelegate(aura::Window* window)
+    : layer_(new ui::Layer(ui::LAYER_TEXTURED)) {
+  layer_->set_delegate(this);
+  layer_->SetBounds(gfx::Rect(-kShadowThick, 0, kShadowThick,
+                              window->bounds().height()));
+  layer_->SetFillsBoundsOpaquely(false);
+  window->layer()->Add(layer_.get());
+}
+
+ShadowLayerDelegate::~ShadowLayerDelegate() {
+}
+
+void ShadowLayerDelegate::OnPaintLayer(gfx::Canvas* canvas) {
+  SkPoint points[2];
+  const SkColor kShadowColors[2] = { kShadowLightColor, kShadowDarkColor };
+
+  points[0].iset(0, 0);
+  points[1].iset(kShadowThick, 0);
+
+  skia::RefPtr<SkShader> shader = skia::AdoptRef(
+      SkGradientShader::CreateLinear(points, kShadowColors, NULL,
+          arraysize(points), SkShader::kRepeat_TileMode, NULL));
+
+  gfx::Rect paint_rect = gfx::Rect(0, 0, kShadowThick,
+                                   layer_->bounds().height());
+  SkPaint paint;
+  paint.setShader(shader.get());
+  canvas->sk_canvas()->drawRect(gfx::RectToSkRect(paint_rect), paint);
+}
+
+void ShadowLayerDelegate::OnDeviceScaleFactorChanged(float scale_factor) {
+}
+
+base::Closure ShadowLayerDelegate::PrepareForLayerBoundsChange() {
+  return base::Bind(&base::DoNothing);
+}
+
+}  // namespace content
diff --git a/content/browser/web_contents/aura/shadow_layer_delegate.h b/content/browser/web_contents/aura/shadow_layer_delegate.h
new file mode 100644
index 0000000..25c2fb4
--- /dev/null
+++ b/content/browser/web_contents/aura/shadow_layer_delegate.h
@@ -0,0 +1,46 @@
+// Copyright (c) 2013 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.
+
+#ifndef CONTENT_BROWSER_WEB_CONTENTS_AURA_SHADOW_LAYER_DELEGATE_H_
+#define CONTENT_BROWSER_WEB_CONTENTS_AURA_SHADOW_LAYER_DELEGATE_H_
+
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/compositor/layer_delegate.h"
+
+namespace aura {
+class Window;
+}
+
+namespace ui {
+class Layer;
+}
+
+namespace content {
+
+// ShadowLayerDelegate takes care of drawing a shadow on the left edge of a
+// window.
+class ShadowLayerDelegate : public ui::LayerDelegate {
+ public:
+  explicit ShadowLayerDelegate(aura::Window* shadow_for);
+  virtual ~ShadowLayerDelegate();
+
+  // Returns the layer for the shadow. Note that the ShadowLayerDelegate owns
+  // the layer, and the layer is destroyed when the delegate is destroyed.
+  ui::Layer* layer() { return layer_.get(); }
+
+ private:
+  // Overridden from ui::LayerDelegate:
+  virtual void OnPaintLayer(gfx::Canvas* canvas) OVERRIDE;
+  virtual void OnDeviceScaleFactorChanged(float device_scale_factor) OVERRIDE;
+  virtual base::Closure PrepareForLayerBoundsChange() OVERRIDE;
+
+  scoped_ptr<ui::Layer> layer_;
+
+  DISALLOW_COPY_AND_ASSIGN(ShadowLayerDelegate);
+};
+
+}  // namespace content
+
+#endif  //  CONTENT_BROWSER_WEB_CONTENTS_AURA_SHADOW_LAYER_DELEGATE_H_