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

cc/pinch_zoom_scrollbar_geometry.cc

Index: cc/pinch_zoom_scrollbar_geometry.cc
diff --git a/cc/pinch_zoom_scrollbar_geometry.cc b/cc/pinch_zoom_scrollbar_geometry.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b7555506c4c0164f43a28614176c49c95db4eed3
--- /dev/null
+++ b/cc/pinch_zoom_scrollbar_geometry.cc
@@ -0,0 +1,126 @@
+// 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_geometry.h"
+
+#include "third_party/WebKit/Source/Platform/chromium/public/WebScrollbar.h"
+
+namespace cc {
+
+const int PinchZoomScrollbarGeometry::kTrackWidth = 10;
+
+WebScrollbarThemeGeometry* PinchZoomScrollbarGeometry::clone() const {
+  return static_cast<WebScrollbarThemeGeometry*>(
+    new PinchZoomScrollbarGeometry());
+}
+
+int PinchZoomScrollbarGeometry::thumbPosition(WebScrollbar* scrollbar) {
+  if (scrollbar->enabled()) {
+    float max_value = scrollbar->maximum();
+    if (!max_value)
+      return 1;
+    int value = std::min(std::max(0, scrollbar->value()), scrollbar->maximum());
+    float pos = (trackLength(scrollbar) - thumbLength(scrollbar)) *
+                value / max_value;
+    return static_cast<int>(floorf((pos > 0 && pos < 1) ? 1 : pos));
+  }
+  return 0;
+}
+
+int PinchZoomScrollbarGeometry::thumbLength(WebScrollbar* scrollbar) {
+  if (!scrollbar->enabled())
+    return 0;
+
+  float size = std::max(scrollbar->size().width, scrollbar->size().height);
+  float proportion = size / scrollbar->totalSize();
+  int track_length = this->trackLength(scrollbar);
+  int length =  proportion * track_length + 0.5f;
+  length = std::max(length, kTrackWidth);
+  if (length > track_length)
+    length = 0;
+  return length;
+}
+
+int PinchZoomScrollbarGeometry::trackPosition(WebScrollbar*) {
+  return 0;
+}
+
+int PinchZoomScrollbarGeometry::trackLength(WebScrollbar* scrollbar) {
+  WebRect track = trackRect(scrollbar);
+  if (scrollbar->orientation() == WebScrollbar::Horizontal)
+    return track.width;
+  else
+    return track.height;
+}
+
+bool PinchZoomScrollbarGeometry::hasButtons(WebScrollbar*) {
+  return false;
+}
+
+bool PinchZoomScrollbarGeometry::hasThumb(WebScrollbar*) {
+  return true;
+}
+
+WebRect PinchZoomScrollbarGeometry::trackRect(WebScrollbar* scrollbar) {
+  int thickness = scrollbarThickness(scrollbar);
+  if (scrollbar->orientation() == WebScrollbar::Horizontal) {
+    return WebRect(scrollbar->location().x, scrollbar->location().y,
+                   scrollbar->size().width, thickness);
+  } else {
+    return WebRect(scrollbar->location().x, scrollbar->location().y,
+                   thickness, scrollbar->size().height);
+  }
+}
+
+WebRect PinchZoomScrollbarGeometry::thumbRect(WebScrollbar* scrollbar) {
+  WebRect track = trackRect(scrollbar);
+  int thumb_pos = thumbPosition(scrollbar);
+  int thickness = scrollbarThickness(scrollbar);
+  if (scrollbar->orientation() == WebScrollbar::Horizontal) {
+    return WebRect(track.x + thumb_pos, track.y + (track.height - thickness) /
+        2, thumbLength(scrollbar), thickness);
+  } else {
+    return WebRect(track.x + (track.width - thickness) / 2, track.y + thumb_pos,
+                   thickness, thumbLength(scrollbar));
+  }
+}
+
+int PinchZoomScrollbarGeometry::minimumThumbLength(WebScrollbar* scrollbar) {
+  return scrollbarThickness(scrollbar);
+}
+
+int PinchZoomScrollbarGeometry::scrollbarThickness(WebScrollbar*) {
+  return kTrackWidth;
+}
+
+WebRect PinchZoomScrollbarGeometry::backButtonStartRect(WebScrollbar*) {
+  return WebRect();
+}
+
+WebRect PinchZoomScrollbarGeometry::backButtonEndRect(WebScrollbar*) {
+  return WebRect();
+}
+
+WebRect PinchZoomScrollbarGeometry::forwardButtonStartRect(WebScrollbar*) {
+  return WebRect();
+}
+
+WebRect PinchZoomScrollbarGeometry::forwardButtonEndRect(WebScrollbar*) {
+  return WebRect();
+}
+
+WebRect PinchZoomScrollbarGeometry::constrainTrackRectToTrackPieces(
+    WebScrollbar*, const WebRect& rect) {
+  return rect;
+}
+
+void PinchZoomScrollbarGeometry::splitTrack(
+    WebScrollbar* scrollbar, const WebRect& track, WebRect& start_track,
+    WebRect& thumb, WebRect& end_track) {
+  thumb = thumbRect(scrollbar);
+  start_track = WebRect();
+  end_track = WebRect();
+}
+
+} // namespace cc