Moving the mouse-wheel processing code out of the FocusManager

chrome/views/focus/focus_manager.cc

 // Copyright (c) 2006-2008 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 <algorithm>
 
 #include "base/histogram.h"
 #include "base/logging.h"
 #include "base/win_util.h"
 #include "chrome/browser/renderer_host/render_widget_host_view_win.h"
@@ skipping 25 matching lines @@
 // Subclassing twice is not a problem if no one is subclassing the HWND between
 // the 2 subclassings (the 2nd subclassing is ignored since the WinProc is the
 // same as the current one).  However if some other app goes and subclasses the
 // HWND between the 2 subclassings, we will end up subclassing twice.
 // This flag lets us test that whether we have or not subclassed yet.
 static const wchar_t* const kFocusSubclassInstalled =
     L"__FOCUS_SUBCLASS_INSTALLED__";
 
 namespace views {
 
-static bool IsCompatibleWithMouseWheelRedirection(HWND window) {
-  std::wstring class_name = win_util::GetClassName(window);
-  // Mousewheel redirection to comboboxes is a surprising and
-  // undesireable user behavior.
-  return !(class_name == L"ComboBox" ||
-           class_name == L"ComboBoxEx32");
-}
-
-static bool CanRedirectMouseWheelFrom(HWND window) {
-  std::wstring class_name = win_util::GetClassName(window);
-
-  // Older Thinkpad mouse wheel drivers create a window under mouse wheel
-  // pointer. Detect if we are dealing with this window. In this case we
-  // don't need to do anything as the Thinkpad mouse driver will send
-  // mouse wheel messages to the right window.
-  if ((class_name == L"Syn Visual Class") ||
-     (class_name == L"SynTrackCursorWindowClass"))
-    return false;
-
-  return true;
-}
-
-bool IsPluginWindow(HWND window) {
-  HWND current_window = window;
-  while (GetWindowLong(current_window, GWL_STYLE) & WS_CHILD) {
-    current_window = GetParent(current_window);
-    if (!IsWindow(current_window))
-      break;
-
-    std::wstring class_name = win_util::GetClassName(current_window);
-    if (class_name == kRenderWidgetHostHWNDClass)
-      return true;
-  }
-
-  return false;
-}
-
-// Forwards mouse wheel messages to the window under it.
-// Windows sends mouse wheel messages to the currently active window.
-// This causes a window to scroll even if it is not currently under the
-// mouse wheel. The following code gives mouse wheel messages to the
-// window under the mouse wheel in order to scroll that window. This
-// is arguably a better user experience.  The returns value says whether
-// the mouse wheel message was successfully redirected.
-static bool RerouteMouseWheel(HWND window, WPARAM wParam, LPARAM lParam) {
-  // Since this is called from a subclass for every window, we can get
-  // here recursively. This will happen if, for example, a control
-  // reflects wheel scroll messages to its parent. Bail out if we got
-  // here recursively.
-  static bool recursion_break = false;
-  if (recursion_break)
-    return false;
-  // Check if this window's class has a bad interaction with rerouting.
-  if (!IsCompatibleWithMouseWheelRedirection(window))
-    return false;
-
-  DWORD current_process = GetCurrentProcessId();
-  POINT wheel_location = { GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) };
-  HWND window_under_wheel = WindowFromPoint(wheel_location);
-
-  if (!CanRedirectMouseWheelFrom(window_under_wheel))
-    return false;
-
-  // Find the lowest Chrome window in the hierarchy that can be the
-  // target of mouse wheel redirection.
-  while (window != window_under_wheel) {
-    // If window_under_wheel is not a valid Chrome window, then return
-    // true to suppress further processing of the message.
-    if (!::IsWindow(window_under_wheel))
-      return true;
-    DWORD wheel_window_process = 0;
-    GetWindowThreadProcessId(window_under_wheel, &wheel_window_process);
-    if (current_process != wheel_window_process) {
-      if (IsChild(window, window_under_wheel)) {
-        // If this message is reflected from a child window in a different
-        // process (happens with out of process windowed plugins) then
-        // we don't want to reroute the wheel message.
-        return false;
-      } else {
-        // The wheel is scrolling over an unrelated window. If that window
-        // is a plugin window in a different chrome then we can send it a
-        // WM_MOUSEWHEEL. Otherwise, we cannot send random WM_MOUSEWHEEL
-        // messages to arbitrary windows. So just drop the message.
-        if (!IsPluginWindow(window_under_wheel))
-          return true;
-      }
-    }
-
-    // window_under_wheel is a Chrome window.  If allowed, redirect.
-    if (IsCompatibleWithMouseWheelRedirection(window_under_wheel)) {
-      recursion_break = true;
-      SendMessage(window_under_wheel, WM_MOUSEWHEEL, wParam, lParam);
-      recursion_break = false;
-      return true;
-    }
-    // If redirection is disallowed, try the parent.
-    window_under_wheel = GetAncestor(window_under_wheel, GA_PARENT);
-  }
-  // If we traversed back to the starting point, we should process
-  // this message normally; return false.
-  return false;
-}
-
 // Callback installed via InstallFocusSubclass.
 static LRESULT CALLBACK FocusWindowCallback(HWND window, UINT message,
                                             WPARAM wParam, LPARAM lParam) {
   if (!::IsWindow(window)) {
     // QEMU has reported crashes when calling GetProp (this seems to happen for
     // some weird messages, not sure what they are).
     // Here we are just trying to avoid the crasher.
     NOTREACHED();
     return 0;
   }
@@ skipping 21 matching lines @@
         // FocusManager::OnActivate attempts to restore the focused view, it
         // needs to be called last so the focus it is setting does not get
         // overridden.
         LRESULT result = CallWindowProc(original_handler, window, WM_ACTIVATE,
                                         wParam, lParam);
         if (!focus_manager->OnPostActivate(window,
                                            LOWORD(wParam), HIWORD(wParam)))
           return 0;
         return result;
       }
-      case WM_MOUSEWHEEL:
-        if (RerouteMouseWheel(window, wParam, lParam))
-          return 0;
-        break;
       case WM_IME_CHAR:
         // Issue 7707: A rich-edit control may crash when it receives a
         // WM_IME_CHAR message while it is processing a WM_IME_COMPOSITION
         // message. Since view controls don't need WM_IME_CHAR messages,
         // we prevent WM_IME_CHAR messages from being dispatched to view
         // controls via the CallWindowProc() call.
         return 0;
       default:
         break;
     }
@@ skipping 638 matching lines @@
       std::find(focus_change_listeners_.begin(), focus_change_listeners_.end(),
                 listener);
   if (place == focus_change_listeners_.end()) {
     NOTREACHED() << "Removing a listener that isn't registered.";
     return;
   }
   focus_change_listeners_.erase(place);
 }
 
 }  // namespace views