[MacViews] Enable dragging a window by its caption/draggable areas.

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 107896f931f200368571f936db5dd58cc4eebeb7..2360d70cce40f40e7d46a162da51ab302120b5ec 100644
--- a/ui/views/cocoa/bridged_native_widget.mm
+++ b/ui/views/cocoa/bridged_native_widget.mm
@@ -10,6 +10,7 @@
 #include "base/mac/mac_util.h"
 #import "base/mac/sdk_forward_declarations.h"
 #include "base/thread_task_runner_handle.h"
+#include "ui/base/hit_test.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ime/input_method_factory.h"
 #include "ui/base/ui_base_switches_util.h"
@@ -19,6 +20,7 @@
 #import "ui/gfx/mac/nswindow_frame_controls.h"
 #include "ui/gfx/screen.h"
 #import "ui/views/cocoa/cocoa_mouse_capture.h"
+#import "ui/views/cocoa/cocoa_non_client_drag.h"
 #import "ui/views/cocoa/bridged_content_view.h"
 #import "ui/views/cocoa/views_nswindow_delegate.h"
 #import "ui/views/cocoa/widget_owner_nswindow_adapter.h"
@@ -92,6 +94,7 @@ gfx::Size BridgedNativeWidget::GetWindowSizeForClientSize(
 
 BridgedNativeWidget::BridgedNativeWidget(NativeWidgetMac* parent)
     : native_widget_mac_(parent),
+      non_client_drag_(new CocoaNonClientDrag()),

[tapted, 2015/05/20 07:18:15]

My suggestion: ditch the reference counting and in the constructor body just do

  // Ensure the event tap is installed that allows windows to be dragged around
  // using their content area.
  CR_DEFINE_STATIC_LOCAL(CocoaNonClientDrag, non_client_drag, ());
  ALLOW_UNUSED_LOCAL(non_client_drag);

[jackhou1, 2015/05/22 02:49:16]

Moved all code to bridged_native_widget.mm.

       focus_manager_(nullptr),
       widget_type_(Widget::InitParams::TYPE_WINDOW),  // Updated in Init().
       parent_(nullptr),
@@ -522,6 +525,46 @@ void BridgedNativeWidget::OnWindowKeyStatusChangedTo(bool is_key) {
   }
 }
 
+bool BridgedNativeWidget::OnWindowWillReceiveLeftMouseDown(
+    NSPoint location_in_window) {
+  BridgedContentView* content_view = [window_ contentView];

[tapted, 2015/05/20 07:18:15]

nit: can just use bridged_view_. I think this will also need an

if (!bridged_view)
  return false;

since events may be received between NativeWidgetMac::Close() (which clears it)
and ~BridgedNativeWidget (which destroys CocoaNonClientDrag to kill the event
tap).

An alternative could be to make non_client_drag a scoped_ptr, and [re]set it in
SetRootView(..).

[jackhou1, 2015/05/22 02:49:16]

Done.

+  bool was_draggable = [content_view mouseDownCanMoveWindow];
+  gfx::Point point(location_in_window.x,
+                   NSHeight([window_ frame]) - location_in_window.y);

[tapted, 2015/05/20 07:18:17]

is this the right thing to flip in? Normally Widget functions expect coordinates
in the content area -- i.e. 

gfx::Point point = [bridged_view_ flipNSRectToRect:location];

might be what you want

[jackhou1, 2015/05/22 02:49:16]

We want to first flip this to a gfx::Point in the windows coordinates. 

NativeWidgetDelegate::GetNonClientComponent says it's in "client" coordinates,
but aura::WindowDelegate::GetNonClientComponent says it's in window coordinates
and directly calls the former. So I think it's okay to be in window coordinates.

Also BridgedContentView doesn't have flipNSRectToRect because it's not a
BaseView. Should it be?

[tapted, 2015/05/22 04:03:11]

I guess so long as it's not out by the size of the titlebar it should be ok.
'tis now :)

+  bool draggable = native_widget_mac()->GetWidget()->GetNonClientComponent(

[tapted, 2015/05/20 07:18:15]

nit: maybe draggable -> should_move_window (I think it reads better below)

[jackhou1, 2015/05/22 02:49:16]

Done.

+                       point) == HTCAPTION;
+  LOG(INFO) << "OnWindowWillReceiveLeftMouseDown " << location_in_window.x
+            << ", " << location_in_window.y << " " << was_draggable << " "
+            << draggable;
+
+  if (was_draggable) {

[tapted, 2015/05/20 07:18:15]

nit: move to the top of the function? i.e.

if (!bridged_view_)
  return false;

if ([bridged_view_ mouseDownCanMoveWindow]) {
  SetDraggable(false);
  return false;
}

gfx::Point point..
bool should_move_window..
if (!should_move_window)
  return false;

etc.

[jackhou1, 2015/05/22 02:49:16]

Done.

+    // This is a re-post, the movement has already completed, so we can make the

[tapted, 2015/05/20 07:18:16]

completed -> started?

(i.e. I think we are still dragging the window after this)

[jackhou1, 2015/05/22 02:49:16]

Done.

+    // window non-draggable again.
+    [content_view setMouseDownCanMoveWindow:NO];
+    // AppKit will not update it's cache of mouseDownCanMoveWindow unless
+    // something changes.

[tapted, 2015/05/20 07:18:17]

is there a private method we could poke to trigger this?

Otherwise I would make this a private method like

BridgedNativeWidget::SetDraggable(bool)

[jackhou1, 2015/05/22 02:49:16]

[NSThemeFrame _resetDragMargins] does something but it comes out buggier, maybe
it only sometimes updates.

Done.

+    base::scoped_nsobject<NSView> temp_view(
+        [[NSView alloc] initWithFrame:[content_view bounds]]);
+    [content_view addSubview:temp_view];
+    [temp_view removeFromSuperview];
+    return false;
+  }
+
+  if (draggable) {
+    // Make the window draggable, then return true to repost the event.
+    [content_view setMouseDownCanMoveWindow:YES];
+    // AppKit will not update it's cache of mouseDownCanMoveWindow unless
+    // something changes.
+    base::scoped_nsobject<NSView> temp_view(
+        [[NSView alloc] initWithFrame:[content_view bounds]]);
+    [content_view addSubview:temp_view];
+    [temp_view removeFromSuperview];
+    return true;
+  }
+
+  return false;
+}
+
 void BridgedNativeWidget::OnSizeConstraintsChanged() {
   NSWindow* window = ns_window();
   Widget* widget = native_widget_mac()->GetWidget();