blob: 1e5d0ca070b395e7dceb070293c31736178c7878 [file] [log] [blame]
// Copyright (c) 2009 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/base/win/mouse_wheel_util.h"
#include "base/auto_reset.h"
#include "base/win/windowsx_shim.h"
#include "ui/base/view_prop.h"
#include "ui/gfx/win/hwnd_util.h"
namespace ui {
// Property used to indicate the HWND supports having mouse wheel messages
// rerouted to it.
static const char* const kHWNDSupportMouseWheelRerouting =
static bool WindowSupportsRerouteMouseWheel(HWND window) {
while (GetWindowLong(window, GWL_STYLE) & WS_CHILD) {
if (!IsWindow(window))
if (ViewProp::GetValue(window, kHWNDSupportMouseWheelRerouting) != NULL) {
return true;
window = GetParent(window);
return false;
static bool IsCompatibleWithMouseWheelRedirection(HWND window) {
std::wstring class_name = gfx::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 = gfx::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;
ViewProp* SetWindowSupportsRerouteMouseWheel(HWND hwnd) {
return new ViewProp(hwnd, kHWNDSupportMouseWheelRerouting,
bool RerouteMouseWheel(HWND window, WPARAM w_param, LPARAM l_param) {
// 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(l_param), GET_Y_LPARAM(l_param) };
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. Make sure that we
// have marked that window as supporting mouse wheel rerouting.
// Otherwise, we cannot send random WM_MOUSEWHEEL messages to arbitrary
// windows. So just drop the message.
if (!WindowSupportsRerouteMouseWheel(window_under_wheel))
return true;
// If the child window is transparent, then it is not interested in
// receiving wheel events.
if (IsChild(window, window_under_wheel) &&
window_under_wheel, GWL_EXSTYLE) & WS_EX_TRANSPARENT) {
return false;
// window_under_wheel is a Chrome window. If allowed, redirect.
if (IsCompatibleWithMouseWheelRedirection(window_under_wheel)) {
base::AutoReset<bool> auto_reset_recursion_break(&recursion_break, true);
SendMessage(window_under_wheel, WM_MOUSEWHEEL, w_param, l_param);
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;
} // namespace ui