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..b19efc144f6af962b7e5b0d46b24458e334ad272
--- /dev/null
+++ b/cc/pinch_zoom_scrollbar_geometry.cc
@@ -0,0 +1,93 @@
+// 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 WebKit {
+
+WebScrollbarThemeGeometry* PinchZoomScrollbarGeometry::clone() const {
+  return static_cast<WebScrollbarThemeGeometry*>(new PinchZoomScrollbarGeometry());

[jamesr, 2013/02/26 20:48:46]

Chromium style line wraps at 80 columns, do that here

[wjmaclean, 2013/03/01 15:30:32]

Done.

+}
+
+int PinchZoomScrollbarGeometry::thumbPosition(WebScrollbar* scrollbar) {
+  if (scrollbar->enabled()) {
+    float size = scrollbar->maximum();
+    if (!size)
+      return 1;
+    int value = std::min(std::max(0, scrollbar->value()), scrollbar->maximum());
+    float pos = (trackLength(scrollbar) - thumbLength(scrollbar)) * value / size;
+    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 trackLength = this->trackLength(scrollbar);
+  int length =  proportion * trackLength + 0.5f;
+  length = std::max(length, kTrackWidth);
+  if (length > trackLength)
+    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;
+}
+
+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 thumbPos = thumbPosition(scrollbar);
+  int thickness = scrollbarThickness(scrollbar);
+  if (scrollbar->orientation() == WebScrollbar::Horizontal)
+    return WebRect(track.x + thumbPos, track.y + (track.height - thickness) / 2,
+                   thumbLength(scrollbar), thickness);
+  else
+    return WebRect(track.x + (track.width - thickness) / 2, track.y + thumbPos,
+                   thickness, thumbLength(scrollbar));
+}
+
+int PinchZoomScrollbarGeometry::minimumThumbLength(WebScrollbar* scrollbar) {
+  return scrollbarThickness(scrollbar);
+}
+
+int PinchZoomScrollbarGeometry::scrollbarThickness(WebScrollbar*) {
+  return kTrackWidth;
+}
+
+WebRect PinchZoomScrollbarGeometry::constrainTrackRectToTrackPieces(WebScrollbar*, const WebRect& rect) {
+  return rect;
+}
+
+void PinchZoomScrollbarGeometry::splitTrack(
+  WebScrollbar* scrollbar, const WebRect& track, WebRect& startTrack, WebRect& thumb,
+  WebRect& endTrack) {
+  thumb = thumbRect(scrollbar);
+  startTrack = WebRect();
+  endTrack = WebRect();
+}
+
+} // namespace WebKit