Add support for taking partial screenshot using touch

ash/wm/partial_screenshot_view.cc

Index: ash/wm/partial_screenshot_view.cc
diff --git a/ash/wm/partial_screenshot_view.cc b/ash/wm/partial_screenshot_view.cc
index 03116e7cf941e30e3b8ef3ecbbbec902a3895c12..03f4d828f04bcd92f5a56b62512c51fc4f58b408 100644
--- a/ash/wm/partial_screenshot_view.cc
+++ b/ash/wm/partial_screenshot_view.cc
@@ -140,6 +140,31 @@ gfx::Rect PartialScreenshotView::GetScreenshotRect() const {
   return gfx::Rect(left, top, width, height);
 }
 
+void PartialScreenshotView::OnSelectionStarted(const gfx::Point& position) {
+  start_position_ = position;
+}
+
+void PartialScreenshotView::OnSelectionChanged(const gfx::Point& position) {
+  current_position_ = position;

[sky, 2013/03/25 23:42:29]

Can this early out if is_dragging_ and current_position_ == position?

[Yufeng Shen (Slow to review), 2013/03/26 01:24:03]

Done.

+  SchedulePaint();
+  is_dragging_ = true;
+}
+
+void PartialScreenshotView::OnSelectionFinished() {
+  overlay_delegate_->Cancel();
+  if (!is_dragging_)
+    return;
+
+  is_dragging_ = false;
+  if (screenshot_delegate_) {
+    aura::RootWindow *root_window =
+        GetWidget()->GetNativeWindow()->GetRootWindow();
+    screenshot_delegate_->HandleTakePartialScreenshot(
+        root_window,
+        gfx::IntersectRects(root_window->bounds(), GetScreenshotRect()));
+  }
+}
+
 gfx::NativeCursor PartialScreenshotView::GetCursor(
     const ui::MouseEvent& event) {
   // Always use "crosshair" cursor.
@@ -167,14 +192,12 @@ bool PartialScreenshotView::OnMousePressed(const ui::MouseEvent& event) {
       Shell::GetInstance()->mouse_cursor_filter();
   mouse_cursor_filter->set_mouse_warp_mode(
       internal::MouseCursorEventFilter::WARP_NONE);
-  start_position_ = event.location();
+  OnSelectionStarted(event.location());
   return true;
 }
 
 bool PartialScreenshotView::OnMouseDragged(const ui::MouseEvent& event) {
-  current_position_ = event.location();
-  SchedulePaint();
-  is_dragging_ = true;
+  OnSelectionChanged(event.location());
   return true;
 }
 
@@ -184,18 +207,27 @@ bool PartialScreenshotView::OnMouseWheel(const ui::MouseWheelEvent& event) {
 }
 
 void PartialScreenshotView::OnMouseReleased(const ui::MouseEvent& event) {
-  overlay_delegate_->Cancel();
-  if (!is_dragging_)
-    return;
+  OnSelectionFinished();

[sky, 2013/03/25 23:42:29]

What about if capture is lost?

[Yufeng Shen (Slow to review), 2013/03/26 01:24:03]

Added OnMouseCaptureLost() which basically cancels the screenshot.

+}
 
-  is_dragging_ = false;
-  if (screenshot_delegate_) {
-    aura::RootWindow *root_window =
-        GetWidget()->GetNativeWindow()->GetRootWindow();
-    screenshot_delegate_->HandleTakePartialScreenshot(
-        root_window,
-        gfx::IntersectRects(root_window->bounds(), GetScreenshotRect()));
+void PartialScreenshotView::OnGestureEvent(ui::GestureEvent* event) {
+  gfx::Point position = event->location();

[sky, 2013/03/25 23:42:29]

const gfx::Point&, although you only use this in two branches, maybe move it to
where needed (meaning 217 and 220).

[Yufeng Shen (Slow to review), 2013/03/26 01:24:03]

Done.

+  switch(event->type()) {
+    case ui::ET_GESTURE_TAP_DOWN:
+      OnSelectionStarted(position);
+      break;
+    case ui::ET_GESTURE_SCROLL_UPDATE:
+      OnSelectionChanged(position);
+      break;
+    case ui::ET_GESTURE_SCROLL_END:
+    case ui::ET_SCROLL_FLING_START:
+      OnSelectionFinished();
+      break;
+    default:
+      break;
   }
+
+  event->SetHandled();
 }
 
 }  // namespace ash