Don't track mouse events in HWNDMessageHandler when they are forwarded by the LegacyRenderWidgetHost

content/browser/renderer_host/legacy_render_widget_host_win.cc

 // Copyright (c) 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 "content/browser/renderer_host/legacy_render_widget_host_win.h"
 
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/win/windows_version.h"
+#include "base/win/win_util.h"
 #include "content/browser/accessibility/browser_accessibility_manager_win.h"
 #include "content/browser/accessibility/browser_accessibility_win.h"
 #include "content/public/common/content_switches.h"
 #include "ui/base/touch/touch_enabled.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace content {
 
 LegacyRenderWidgetHostHWND::~LegacyRenderWidgetHostHWND() {
   ::DestroyWindow(hwnd());
 }
 
 // static
 scoped_ptr<LegacyRenderWidgetHostHWND> LegacyRenderWidgetHostHWND::Create(
     HWND parent) {
+  if (CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableLegacyIntermediateWindow))
+    return scoped_ptr<LegacyRenderWidgetHostHWND>();
+
   scoped_ptr<LegacyRenderWidgetHostHWND> legacy_window_instance;
   legacy_window_instance.reset(new LegacyRenderWidgetHostHWND(parent));
   // If we failed to create the child, or if the switch to disable the legacy
   // window is passed in, then return NULL.
-  if (!::IsWindow(legacy_window_instance->hwnd()) ||
-      CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kDisableLegacyIntermediateWindow))
+  if (!::IsWindow(legacy_window_instance->hwnd()))
     return scoped_ptr<LegacyRenderWidgetHostHWND>();
 
   legacy_window_instance->Init();
   return legacy_window_instance.Pass();
 }
 
 void LegacyRenderWidgetHostHWND::UpdateParent(HWND parent) {
   ::SetParent(hwnd(), parent);
   // If the new parent is the desktop Window, then we disable the child window
   // to ensure that it does not receive any input events. It should not because
@@ skipping 81 matching lines @@
                                                     WPARAM w_param,
                                                     LPARAM l_param,
                                                     BOOL& handled) {
   return ::SendMessage(GetParent(), message, w_param, l_param);
 }
 
 LRESULT LegacyRenderWidgetHostHWND::OnMouseRange(UINT message,
                                                  WPARAM w_param,
                                                  LPARAM l_param,
                                                  BOOL& handled) {
-  POINT mouse_coords;
-  mouse_coords.x = GET_X_LPARAM(l_param);
-  mouse_coords.y = GET_Y_LPARAM(l_param);
-  ::MapWindowPoints(hwnd(), GetParent(), &mouse_coords, 1);
-  return ::SendMessage(GetParent(), message, w_param,
-                       MAKELPARAM(mouse_coords.x, mouse_coords.y));
+  // Mark the WM_MOUSEMOVE message with a special flag 0xbeef in the high word

[sky, 2014/02/12 22:51:29]

nit nuke 0xbeef, since you really mean SPECIAL_MOUSEMOVED_NOT_TO_B...

[ananta, 2014/02/12 23:17:08]

Done.

+  // of the WPARAM.
+  // The parent window has code to track mouse events, i.e to detect if the
+  // cursor left the bounds of the parent window. Technically entering a child
+  // window indicates that the cursor left the parent window.
+  // To ensure that the parent does not turn on tracking for the WM_MOUSEMOVE
+  // messages sent from us, we flag this in the WPARAM.
+  if (message == WM_MOUSEMOVE)
+    w_param = MAKEWPARAM(LOWORD(w_param), SPECIAL_MOUSEMOVE_NOT_TO_BE_TRACKED);
+
+  // The offsets in mouse wheel messages are in screen coordinates. We should
+  // not be converting them to parent coordinates.
+  if (message != WM_MOUSEWHEEL && message != WM_MOUSEHWHEEL) {
+    POINT mouse_coords;
+    mouse_coords.x = GET_X_LPARAM(l_param);
+    mouse_coords.y = GET_Y_LPARAM(l_param);
+    ::MapWindowPoints(hwnd(), GetParent(), &mouse_coords, 1);
+    l_param = MAKELPARAM(mouse_coords.x, mouse_coords.y);
+  }
+  return ::SendMessage(GetParent(), message, w_param, l_param);
 }
 
 LRESULT LegacyRenderWidgetHostHWND::OnMouseActivate(UINT message,
                                                     WPARAM w_param,
                                                     LPARAM l_param) {
   // Don't pass this to DefWindowProc. That results in the WM_MOUSEACTIVATE
   // message going all the way to the parent which then messes up state
   // related to focused views, etc. This is because it treats this as if
   // it lost activation.
   // Our dummy window should not interfere with focus and activation in
@@ skipping 26 matching lines @@
   return 0;
 }
 
 LRESULT LegacyRenderWidgetHostHWND::OnSetCursor(UINT message,
                                                 WPARAM w_param,
                                                 LPARAM l_param) {
   return 0;
 }
 
 }  // namespace content