MacViews: Implement Tab Dragging

ui/views/cocoa/bridged_native_widget.mm

Index: ui/views/cocoa/bridged_native_widget.mm
diff --git a/ui/views/cocoa/bridged_native_widget.mm b/ui/views/cocoa/bridged_native_widget.mm
index 1c9560f2e8834aeb19225abd760819145854b361..8d5518c6358f5744c1a58debcb396542482132f4 100644
--- a/ui/views/cocoa/bridged_native_widget.mm
+++ b/ui/views/cocoa/bridged_native_widget.mm
@@ -25,6 +25,7 @@
 #import "ui/gfx/mac/nswindow_frame_controls.h"
 #import "ui/views/cocoa/bridged_content_view.h"
 #import "ui/views/cocoa/cocoa_mouse_capture.h"
+#import "ui/views/cocoa/cocoa_window_move_loop.h"
 #include "ui/views/cocoa/tooltip_manager_mac.h"
 #import "ui/views/cocoa/views_nswindow_delegate.h"
 #import "ui/views/cocoa/widget_owner_nswindow_adapter.h"
@@ -615,6 +616,39 @@ bool BridgedNativeWidget::HasCapture() {
   return mouse_capture_ && mouse_capture_->IsActive();
 }
 
+Widget::MoveLoopResult BridgedNativeWidget::RunMoveLoop(
+      const gfx::Vector2d& drag_offset) {
+  DCHECK(!HasCapture());
+  DCHECK(!window_move_loop_);
+
+  // RunMoveLoop caller is responsible for updating the window to be under the
+  // mouse, but it does this using possibly outdated coordinate from the mouse
+  // event, and mouse is very likely moved beyound that point.
+
+  // Compensate for mouse drift by shifting the initial mouse position we pass
+  // to CocoaWindowMoveLoop, so as it handles incoming move events the window's
+  // top left corner will be |drag_offset| from the current mouse position.
+
+  const gfx::Rect frame = gfx::ScreenRectFromNSRect([window_ frame]);
+  const gfx::Point mouse_in_screen(frame.x() + drag_offset.x(),
+                                   frame.y() + drag_offset.y());
+  window_move_loop_.reset(new CocoaWindowMoveLoop(
+      this, gfx::ScreenPointToNSPoint(mouse_in_screen)));
+
+  return window_move_loop_->Run();
+
+  // |this| may be destroyed during the RunLoop, causing it to exit early.
+  // Even if that doesn't happen, CocoaWindowMoveLoop will clean itself up by
+  // calling EndMoveLoop(). So window_move_loop_ will always be null before the
+  // function returns. But don't DCHECK since |this| might not be valid.
+}
+
+void BridgedNativeWidget::EndMoveLoop() {
+  DCHECK(window_move_loop_);
+  window_move_loop_->End();
+  window_move_loop_.reset();
+}
+
 void BridgedNativeWidget::SetNativeWindowProperty(const char* name,
                                                   void* value) {
   NSString* key = [NSString stringWithUTF8String:name];
@@ -733,6 +767,10 @@ void BridgedNativeWidget::OnSizeChanged() {
     [bridged_view_ updateWindowMask];
 }
 
+void BridgedNativeWidget::OnPositionChanged() {
+  native_widget_mac_->GetWidget()->OnNativeWidgetMove();
+}
+
 void BridgedNativeWidget::OnVisibilityChanged() {
   OnVisibilityChangedTo([window_ isVisible]);
 }