Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/pinch_zoom_scrollbar.cc

Index: cc/pinch_zoom_scrollbar.cc
diff --git a/cc/pinch_zoom_scrollbar.cc b/cc/pinch_zoom_scrollbar.cc
new file mode 100644
index 0000000000000000000000000000000000000000..273e5d050b7e81155a8d59af6fef66dc9662840d
--- /dev/null
+++ b/cc/pinch_zoom_scrollbar.cc
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+// Copyright 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 "cc/pinch_zoom_scrollbar.h"
+
+#include "cc/layer.h"
+#include "cc/layer_tree_host.h"
+#include "cc/pinch_zoom_scrollbar_geometry.h"
+
+namespace cc {
+
+const float PinchZoomScrollbar::kDefaultOpacity = 0.5;
+const float PinchZoomScrollbar::kFadeDurationInSeconds = 0.5;
+
+PinchZoomScrollbar::PinchZoomScrollbar(
+    WebKit::WebScrollbar::Orientation orientation, LayerTreeHost* owner)
+  : orientation_(orientation),
+    owner_(owner) {
+  DCHECK(owner_);
+}
+
+
+bool PinchZoomScrollbar::isOverlay() const { return true; }
+
+int PinchZoomScrollbar::value() const {
+  const Layer* root_scroll_layer = owner_->rootScrollLayer();
+  if (!root_scroll_layer)
+    return 0;
+
+  if (orientation_ == WebKit::WebScrollbar::Horizontal)
+    return root_scroll_layer->scrollOffset().x();
+  else
+    return root_scroll_layer->scrollOffset().y();
+}
+
+WebKit::WebPoint PinchZoomScrollbar::location() const {
+  return WebKit::WebPoint();
+}
+
+WebKit::WebSize PinchZoomScrollbar::size() const {
+  gfx::Size viewport_size = owner_->layoutViewportSize();
+  gfx::Size size;
+  int track_width = PinchZoomScrollbarGeometry::kTrackWidth;
+  if (orientation_ == WebKit::WebScrollbar::Horizontal)
+    size = gfx::Size(viewport_size.width() - track_width, track_width);
+  else
+    size = gfx::Size(track_width, viewport_size.height() - track_width);
+  return WebKit::WebSize(size);
+}
+
+bool PinchZoomScrollbar::enabled() const {
+    return true;
+}
+
+int PinchZoomScrollbar::maximum() const {
+  gfx::Size size = owner_->layoutViewportSize();
+  const Layer* root_scroll_layer = owner_->rootScrollLayer();
+  if (!root_scroll_layer)
+    return 0;
+
+  if (orientation_ == WebKit::WebScrollbar::Horizontal)
+    return root_scroll_layer->contentBounds().width() - size.width();
+  else
+    return root_scroll_layer->contentBounds().height() - size.height();
+}
+
+int PinchZoomScrollbar::totalSize() const {
+  const Layer* root_scroll_layer = owner_->rootScrollLayer();
+  gfx::Size size;
+  if (root_scroll_layer)
+    size = root_scroll_layer->contentBounds();
+  else
+    size = owner_->layoutViewportSize();

[enne (OOO), 2013/03/07 23:41:17]

This if statement doesn't make any sense.  You can't mix contentBounds and
layoutViewportSize.  Perhaps the totalSize should be zero if there's no root
scroll layer?

[wjmaclean, 2013/03/08 15:28:57]

Done.

+
+  if (orientation_ == WebKit::WebScrollbar::Horizontal)
+    return size.width();
+  else
+    return size.height();
+}
+
+bool PinchZoomScrollbar::isScrollViewScrollbar() const {
+    return false;
+}
+
+bool PinchZoomScrollbar::isScrollableAreaActive() const {
+    return true;
+}
+
+WebKit::WebScrollbar::ScrollbarControlSize PinchZoomScrollbar::controlSize() const {
+    return WebKit::WebScrollbar::SmallScrollbar;
+}
+
+WebKit::WebScrollbar::ScrollbarPart PinchZoomScrollbar::pressedPart() const {
+    return WebKit::WebScrollbar::NoPart;
+}
+
+WebKit::WebScrollbar::ScrollbarPart PinchZoomScrollbar::hoveredPart() const {
+    return WebKit::WebScrollbar::NoPart;
+}
+
+WebKit::WebScrollbar::ScrollbarOverlayStyle PinchZoomScrollbar::scrollbarOverlayStyle() const {
+    return WebKit::WebScrollbar::ScrollbarOverlayStyleDefault;
+}
+bool PinchZoomScrollbar::isCustomScrollbar() const {
+    return false;
+}
+
+WebKit::WebScrollbar::Orientation PinchZoomScrollbar::orientation() const {
+    return orientation_;
+}
+
+}  // namespace cc