Fix tab drag and drop with hi-dpi.

ui/views/widget/desktop_aura/x11_topmost_window_finder.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/widget/desktop_aura/x11_topmost_window_finder.h"
 
 #include <X11/Xutil.h>
 
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/window.h"
+#include "ui/gfx/screen.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h"
 
 namespace views {
 
+float GetDeviceScaleFactor() {
+  gfx::Display display = gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
+  return display.device_scale_factor();
+}
+
+gfx::Point ScreenToDIPPoint(const gfx::Point& pixel_point) {
+  return ToFlooredPoint(ScalePoint(pixel_point, 1.0f / GetDeviceScaleFactor()));
+}
+
+gfx::Point DIPToScreenPoint(const gfx::Point& dip_point) {
+  return ToFlooredPoint(gfx::ScalePoint(dip_point, GetDeviceScaleFactor()));
+}
+
 X11TopmostWindowFinder::X11TopmostWindowFinder() : toplevel_(None) {
 }
 
 X11TopmostWindowFinder::~X11TopmostWindowFinder() {
 }
 
 aura::Window* X11TopmostWindowFinder::FindLocalProcessWindowAt(
     const gfx::Point& screen_loc,
     const std::set<aura::Window*>& ignore) {
-  screen_loc_ = screen_loc;
+  screen_loc_ = DIPToScreenPoint(screen_loc);
   ignore_ = ignore;
 
   std::vector<aura::Window*> local_process_windows =
       DesktopWindowTreeHostX11::GetAllOpenWindows();
   bool found_local_process_window = false;
   for (size_t i = 0; i < local_process_windows.size(); ++i) {
     if (ShouldStopIteratingAtLocalProcessWindow(local_process_windows[i])) {
       found_local_process_window = true;
       break;
     }
   }
   if (!found_local_process_window)
     return NULL;
 
   ui::EnumerateTopLevelWindows(this);
   return DesktopWindowTreeHostX11::GetContentWindowForXID(toplevel_);
 }
 
 XID X11TopmostWindowFinder::FindWindowAt(const gfx::Point& screen_loc) {
-  screen_loc_ = screen_loc;
+  screen_loc_ = DIPToScreenPoint(screen_loc);

[sadrul, 2015/03/17 15:56:06]

From some of the callsites, the |screen_loc| looks like it should already be in
pixels?

[stapelberg, 2015/03/19 08:25:44]

You’re right. Reverted that part of the change.

   ui::EnumerateTopLevelWindows(this);
   return toplevel_;
 }
 
 bool X11TopmostWindowFinder::ShouldStopIterating(XID xid) {
   if (!ui::IsWindowVisible(xid))
     return false;
 
   aura::Window* window =
       views::DesktopWindowTreeHostX11::GetContentWindowForXID(xid);
@@ skipping 33 matching lines @@
     return true;
 
   aura::client::ScreenPositionClient* screen_position_client =
       aura::client::GetScreenPositionClient(window->GetRootWindow());
   gfx::Point window_loc(screen_loc_);
   screen_position_client->ConvertPointFromScreen(window, &window_loc);
   return XPointInRegion(shape, window_loc.x(), window_loc.y()) == True;
 }
 
 }  // namespace views