Create drag windows on all displays

ash/wm/drag_window_resizer.cc

Index: ash/wm/drag_window_resizer.cc
diff --git a/ash/wm/drag_window_resizer.cc b/ash/wm/drag_window_resizer.cc
index 765dd172959d6eb05cb4c4616f3e1435dcc8a069..0145fbbfae30a631d0374c0dac558bc26f5ca6a0 100644
--- a/ash/wm/drag_window_resizer.cc
+++ b/ash/wm/drag_window_resizer.cc
@@ -24,31 +24,6 @@
 #include "ui/wm/core/window_util.h"
 
 namespace ash {
-namespace {
-
-// The maximum opacity of the drag phantom window.
-const float kMaxOpacity = 0.8f;
-
-// Returns true if Ash has more than one root window.
-bool HasSecondaryRootWindows() {
-  return Shell::GetAllRootWindows().size() > 1;
-}
-
-// When there are more than one root windows, returns all root windows which are
-// not |root_window|. Returns an empty vector if only one root window exists.
-aura::Window::Windows GetOtherRootWindows(aura::Window* root_window) {
-  aura::Window::Windows root_windows = Shell::GetAllRootWindows();
-  aura::Window::Windows other_root_windows;
-  if (root_windows.size() < 2)
-    return other_root_windows;
-  for (size_t i = 0; i < root_windows.size(); ++i) {
-    if (root_windows[i] != root_window)
-      other_root_windows.push_back(root_windows[i]);
-  }
-  return other_root_windows;
-}
-
-}  // namespace
 
 // static
 DragWindowResizer* DragWindowResizer::instance_ = NULL;
@@ -79,14 +54,12 @@ void DragWindowResizer::Drag(const gfx::Point& location, int event_flags) {
 
   last_mouse_location_ = location;
   // Show a phantom window for dragging in another root window.
-  if (HasSecondaryRootWindows()) {
+  if (gfx::Screen::GetScreen()->GetNumDisplays() > 1) {
     gfx::Point location_in_screen = location;
     ::wm::ConvertPointToScreen(GetTarget()->parent(), &location_in_screen);
-    const bool in_original_root =
-        wm::GetRootWindowAt(location_in_screen) == GetTarget()->GetRootWindow();
-    UpdateDragWindow(GetTarget()->bounds(), in_original_root);
+    UpdateDragWindow(GetTarget()->bounds(), location_in_screen);
   } else {
-    drag_window_controllers_.clear();
+    drag_window_controller_.reset();
   }
 }
 
@@ -94,7 +67,7 @@ void DragWindowResizer::CompleteDrag() {
   next_window_resizer_->CompleteDrag();
 
   GetTarget()->layer()->SetOpacity(details().initial_opacity);
-  drag_window_controllers_.clear();
+  drag_window_controller_.reset();
 
   // Check if the destination is another display.
   gfx::Point last_mouse_location_in_screen = last_mouse_location_;
@@ -139,7 +112,7 @@ void DragWindowResizer::CompleteDrag() {
 void DragWindowResizer::RevertDrag() {
   next_window_resizer_->RevertDrag();
 
-  drag_window_controllers_.clear();
+  drag_window_controller_.reset();
   GetTarget()->layer()->SetOpacity(details().initial_opacity);
 }
 
@@ -161,58 +134,29 @@ DragWindowResizer::DragWindowResizer(WindowResizer* next_window_resizer,
   instance_ = this;
 }
 
-void DragWindowResizer::UpdateDragWindow(const gfx::Rect& bounds,
-                                         bool in_original_root) {
+void DragWindowResizer::UpdateDragWindow(
+    const gfx::Rect& bounds_in_parent,
+    const gfx::Point& drag_location_in_screen) {
   if (details().window_component != HTCAPTION || !ShouldAllowMouseWarp())
     return;
 
-  // It's available. Show a phantom window on the display if needed.
-  aura::Window::Windows other_roots =
-      GetOtherRootWindows(GetTarget()->GetRootWindow());
-  size_t drag_window_controller_count = 0;
-  for (size_t i = 0; i < other_roots.size(); ++i) {
-    aura::Window* another_root = other_roots[i];
-    const gfx::Rect root_bounds_in_screen(another_root->GetBoundsInScreen());
-    const gfx::Rect bounds_in_screen =
-      ScreenUtil::ConvertRectToScreen(GetTarget()->parent(), bounds);
-    gfx::Rect bounds_in_another_root =
-        gfx::IntersectRects(root_bounds_in_screen, bounds_in_screen);
-    const float fraction_in_another_window =
-        (bounds_in_another_root.width() * bounds_in_another_root.height()) /
-        static_cast<float>(bounds.width() * bounds.height());
-
-    if (fraction_in_another_window > 0) {
-      if (drag_window_controllers_.size() < ++drag_window_controller_count)
-        drag_window_controllers_.resize(drag_window_controller_count);
-      ScopedVector<DragWindowController>::reference drag_window_controller =
-        drag_window_controllers_.back();
-      if (!drag_window_controller) {
-        drag_window_controller = new DragWindowController(GetTarget());
-        // Always show the drag phantom on the |another_root| window.
-        drag_window_controller->SetDestinationDisplay(
-            gfx::Screen::GetScreen()->GetDisplayNearestWindow(another_root));
-        drag_window_controller->Show();
-      } else {
-        // No animation.
-        drag_window_controller->SetBounds(bounds_in_screen);
-      }
-      const float phantom_opacity =
-          !in_original_root ? 1 : (kMaxOpacity * fraction_in_another_window);
-      const float window_opacity =
-          in_original_root ? 1
-                           : (kMaxOpacity * (1 - fraction_in_another_window));
-      drag_window_controller->SetOpacity(phantom_opacity);
-      GetTarget()->layer()->SetOpacity(window_opacity);
-    } else {
-      GetTarget()->layer()->SetOpacity(1.0f);
-    }
-  }
+  if (!drag_window_controller_)
+    drag_window_controller_.reset(new DragWindowController(GetTarget()));
 
-  // If we have more drag window controllers allocated than needed, release the
-  // excess controllers by shrinking the vector |drag_window_controller_|.
-  DCHECK_GE(drag_window_controllers_.size(), drag_window_controller_count);
-  if (drag_window_controllers_.size() > drag_window_controller_count)
-    drag_window_controllers_.resize(drag_window_controller_count);
+  const gfx::Rect bounds_in_screen =
+      ScreenUtil::ConvertRectToScreen(GetTarget()->parent(), bounds_in_parent);
+
+  gfx::Rect root_bounds_in_screen =
+      GetTarget()->GetRootWindow()->GetBoundsInScreen();
+  float opacity = 1.0f;
+  if (!root_bounds_in_screen.Contains(drag_location_in_screen)) {
+    gfx::Rect visible_bounds = root_bounds_in_screen;
+    visible_bounds.Intersect(bounds_in_screen);
+    opacity = DragWindowController::GetDragWindowOpacity(bounds_in_screen,
+                                                         visible_bounds);
+  }
+  GetTarget()->layer()->SetOpacity(opacity);
+  drag_window_controller_->Update(bounds_in_screen, drag_location_in_screen);
 }
 
 bool DragWindowResizer::ShouldAllowMouseWarp() {