Magnifier: Support wrapping the cursor between extended monitors

ash/magnifier/magnification_controller.cc

Index: ash/magnifier/magnification_controller.cc
diff --git a/ash/magnifier/magnification_controller.cc b/ash/magnifier/magnification_controller.cc
index ff2ea926b665153300329b47800ab16596c0e48c..83f47e4546f3e9d28a93b82e838c3593b63606a6 100644
--- a/ash/magnifier/magnification_controller.cc
+++ b/ash/magnifier/magnification_controller.cc
@@ -79,6 +79,12 @@ class MagnificationControllerImpl : virtual public MagnificationController,
                                      bool animate);
   void OnMouseMove(const gfx::Point& location);
 
+  // Switch Magnified RootWindow to |new_root_window|. This does following:
+  //  - Unzoom the current root_window.
+  //  - Zoom the given new root_window |new_root_window|.
+  //  - Switch the target window from current window to |new_root_window|.
+  void SwitchTargetRootWindow(aura::RootWindow* new_root_window);
+
   // Returns if the magnification scale is 1.0 or not (larger then 1.0).
   bool IsMagnified() const;
 
@@ -161,11 +167,12 @@ bool MagnificationControllerImpl::RedrawDIP(const gfx::Point& position_in_dip,
   if (y > max_y)
     y = max_y;
 
-  // Ignores 1 px diffirence because it may be error on calculation.
-  if (std::abs(origin_.x() - x) <= 1 &&
-      std::abs(origin_.y() - y) <= 1 &&
-      scale == scale_)
+  // Does nothing if both the origin and the scale are not changed.
+  if (origin_.x() == x  &&
+      origin_.y() == y &&
+      scale == scale_) {
     return false;
+  }
 
   origin_.set_x(x);
   origin_.set_y(y);
@@ -333,6 +340,18 @@ void MagnificationControllerImpl::OnImplicitAnimationsCompleted() {
   is_on_zooming_ = false;
 }
 
+void MagnificationControllerImpl::SwitchTargetRootWindow(
+    aura::RootWindow* new_root_window) {
+  if (new_root_window == root_window_)
+    return;
+
+  float scale = GetScale();
+
+  SetScale(1.0f, true);
+  root_window_ = new_root_window;
+  SetScale(scale, true);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // MagnificationControllerImpl: MagnificationController implementation
 
@@ -342,11 +361,10 @@ void MagnificationControllerImpl::SetScale(float scale, bool animate) {
 
   ValidateScale(&scale);
 
-  // Try not to change the point which the mouse cursor indicates to.
-  const gfx::Rect window_rect = GetWindowRectDIP(scale);
-  const gfx::Point mouse = gfx::Screen::GetCursorScreenPoint();
-  const gfx::Point origin = gfx::Point(mouse.x() * (1.0f - 1.0f / scale),
-                                       mouse.y() * (1.0f - 1.0f / scale));
+  gfx::Point mouse_in_root = root_window_->GetLastMouseLocationInRoot();
+  const gfx::Point origin =
+      gfx::Point(mouse_in_root.x() * (1.0f - 1.0f / scale),
+                 mouse_in_root.y() * (1.0f - 1.0f / scale));
   Redraw(origin, scale, animate);
 }
 
@@ -403,8 +421,18 @@ bool MagnificationControllerImpl::PreHandleKeyEvent(aura::Window* target,
 
 bool MagnificationControllerImpl::PreHandleMouseEvent(aura::Window* target,
                                                       aura::MouseEvent* event) {
-  if (IsMagnified() && event->type() == ui::ET_MOUSE_MOVED)
-    OnMouseMove(event->root_location());
+  if (IsMagnified() && event->type() == ui::ET_MOUSE_MOVED) {
+    aura::RootWindow* current_root = target->GetRootWindow();
+    gfx::Rect root_bounds = current_root->bounds();
+
+    if (root_bounds.Contains(event->root_location())) {
+      if (current_root != root_window_)
+        SwitchTargetRootWindow(current_root);
+
+      OnMouseMove(event->root_location());
+    }
+  }
+
   return false;
 }