Introduces a new scrollbar for message_center.

ui/views/controls/scrollbar/overlay_scroll_bar.cc

Index: ui/views/controls/scrollbar/overlay_scroll_bar.cc
diff --git a/ui/views/controls/scrollbar/overlay_scroll_bar.cc b/ui/views/controls/scrollbar/overlay_scroll_bar.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ef05acc559f99a700ef866a7d41c520b6cc6776b
--- /dev/null
+++ b/ui/views/controls/scrollbar/overlay_scroll_bar.cc
@@ -0,0 +1,148 @@
+// 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 "ui/views/controls/scrollbar/overlay_scroll_bar.h"
+
+#include "third_party/skia/include/core/SkColor.h"
+#include "third_party/skia/include/core/SkXfermode.h"
+#include "ui/gfx/canvas.h"
+#include "ui/views/background.h"
+#include "ui/views/border.h"
+#include "ui/views/controls/scrollbar/base_scroll_bar_thumb.h"
+
+namespace views {
+namespace {
+
+const int kScrollbarWidth = 10;
+const int kThumbInsetInside = 3;
+const int kThumbInsetFromEdge = 1;
+const int kThumbCornerRadius = 2;
+const int kThumbMinimumSize = kScrollbarWidth;
+const int kThumbHoverAlpha = 128;
+const int kThumbDefaultAlpha = 64;
+
+class OverlayScrollBarThumb : public BaseScrollBarThumb,
+                              public ui::AnimationDelegate {
+ public:
+  explicit OverlayScrollBarThumb(BaseScrollBar* scroll_bar);
+  virtual ~OverlayScrollBarThumb();
+
+ protected:
+  // View overrides:
+  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
+
+  // ui::AnimationDelegate overrides:
+  virtual void AnimationProgressed(const ui::Animation* animation) OVERRIDE;
+
+ private:
+  double animation_opacity_;
+  DISALLOW_COPY_AND_ASSIGN(OverlayScrollBarThumb);
+};
+
+OverlayScrollBarThumb::OverlayScrollBarThumb(BaseScrollBar* scroll_bar)
+    : BaseScrollBarThumb(scroll_bar),
+      animation_opacity_(0.0) {
+  if (get_use_acceleration_when_possible()) {
+    // This is necessary, otherwise the thumb will be rendered below the views
+    // if those views paint to their own layers.
+    SetPaintToLayer(true);
+    SetFillsBoundsOpaquely(false);
+  }
+}
+
+OverlayScrollBarThumb::~OverlayScrollBarThumb() {
+}
+
+gfx::Size OverlayScrollBarThumb::GetPreferredSize() {
+  return gfx::Size(kThumbMinimumSize, kThumbMinimumSize);
+}
+
+void OverlayScrollBarThumb::OnPaint(gfx::Canvas* canvas) {
+  gfx::Rect local_bounds(GetLocalBounds());
+  SkPaint paint;
+  int alpha = (GetState() == CustomButton::STATE_HOVERED ||
+               GetState() == CustomButton::STATE_PRESSED) ?
+      kThumbHoverAlpha : kThumbDefaultAlpha;
+  alpha *= animation_opacity_;
+  paint.setStyle(SkPaint::kFill_Style);
+  paint.setColor(SkColorSetARGB(alpha, 0, 0, 0));
+  canvas->DrawRoundRect(local_bounds, kThumbCornerRadius, paint);
+}
+
+void OverlayScrollBarThumb::AnimationProgressed(
+    const ui::Animation* animation) {
+  animation_opacity_ = animation->GetCurrentValue();
+  SchedulePaint();
+}
+
+}  // namespace
+
+OverlayScrollBar::OverlayScrollBar(bool horizontal)
+    : BaseScrollBar(horizontal, new OverlayScrollBarThumb(this)),
+      animation_(static_cast<OverlayScrollBarThumb*>(GetThumb())) {
+  set_notify_enter_exit_on_child(true);
+}
+
+OverlayScrollBar::~OverlayScrollBar() {
+}
+
+gfx::Rect OverlayScrollBar::GetTrackBounds() const {
+  gfx::Rect local_bounds(GetLocalBounds());
+  if (IsHorizontal()) {
+    local_bounds.Inset(kThumbInsetFromEdge, kThumbInsetInside,
+                       kThumbInsetFromEdge, kThumbInsetFromEdge);
+  } else {
+    local_bounds.Inset(kThumbInsetInside, kThumbInsetFromEdge,
+                       kThumbInsetFromEdge, kThumbInsetFromEdge);
+  }
+  gfx::Size track_size = local_bounds.size();
+  track_size.SetToMax(GetThumb()->size());
+  local_bounds.set_size(track_size);
+  return local_bounds;
+}
+
+int OverlayScrollBar::GetLayoutSize() const {
+  return 0;
+}
+
+int OverlayScrollBar::GetContentOverlapSize() const {
+  return kScrollbarWidth;
+}
+
+void OverlayScrollBar::OnMouseEnteredScrollView(const ui::MouseEvent& event) {
+  if (GetThumb()->layer())
+    animation_.Show();
+  else
+    GetThumb()->SetVisible(true);
+}
+
+void OverlayScrollBar::OnMouseExitedScrollView(const ui::MouseEvent& event) {
+  if (GetThumb()->layer())
+    animation_.Hide();
+  else
+    GetThumb()->SetVisible(false);
+}
+
+gfx::Size OverlayScrollBar::GetPreferredSize() {
+  return gfx::Size();
+}
+
+void OverlayScrollBar::Layout() {
+  gfx::Rect thumb_bounds = GetTrackBounds();
+  BaseScrollBarThumb* thumb = GetThumb();
+  if (IsHorizontal()) {
+    thumb_bounds.set_x(thumb->x());
+    thumb_bounds.set_width(thumb->width());
+  } else {
+    thumb_bounds.set_y(thumb->y());
+    thumb_bounds.set_height(thumb->height());
+  }
+  thumb->SetBoundsRect(thumb_bounds);
+}
+
+void OverlayScrollBar::OnPaint(gfx::Canvas* canvas) {
+}
+
+}  // namespace views