1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "ui/base/win/mouse_wheel_util.h"
6
7 #include <windowsx.h>
8
9 #include "base/auto_reset.h"
10 #include "ui/base/view_prop.h"
11 #include "ui/gfx/win/hwnd_util.h"
12
13 namespace ui {
14
15 // Property used to indicate the HWND supports having mouse wheel messages
16 // rerouted to it.
17 static const char* const kHWNDSupportMouseWheelRerouting =
18 "__HWND_MW_REROUTE_OK";
19
WindowSupportsRerouteMouseWheel(HWND window)20 static bool WindowSupportsRerouteMouseWheel(HWND window) {
21 while (GetWindowLong(window, GWL_STYLE) & WS_CHILD) {
22 if (!IsWindow(window))
23 break;
24
25 if (ViewProp::GetValue(window, kHWNDSupportMouseWheelRerouting) != NULL) {
26 return true;
27 }
28 window = GetParent(window);
29 }
30 return false;
31 }
32
IsCompatibleWithMouseWheelRedirection(HWND window)33 static bool IsCompatibleWithMouseWheelRedirection(HWND window) {
34 std::wstring class_name = gfx::GetClassName(window);
35 // Mousewheel redirection to comboboxes is a surprising and
36 // undesireable user behavior.
37 return !(class_name == L"ComboBox" ||
38 class_name == L"ComboBoxEx32");
39 }
40
CanRedirectMouseWheelFrom(HWND window)41 static bool CanRedirectMouseWheelFrom(HWND window) {
42 std::wstring class_name = gfx::GetClassName(window);
43
44 // Older Thinkpad mouse wheel drivers create a window under mouse wheel
45 // pointer. Detect if we are dealing with this window. In this case we
46 // don't need to do anything as the Thinkpad mouse driver will send
47 // mouse wheel messages to the right window.
48 if ((class_name == L"Syn Visual Class") ||
49 (class_name == L"SynTrackCursorWindowClass"))
50 return false;
51
52 return true;
53 }
54
SetWindowSupportsRerouteMouseWheel(HWND hwnd)55 ViewProp* SetWindowSupportsRerouteMouseWheel(HWND hwnd) {
56 return new ViewProp(hwnd, kHWNDSupportMouseWheelRerouting,
57 reinterpret_cast<HANDLE>(true));
58 }
59
RerouteMouseWheel(HWND window,WPARAM w_param,LPARAM l_param)60 bool RerouteMouseWheel(HWND window, WPARAM w_param, LPARAM l_param) {
61 // Since this is called from a subclass for every window, we can get
62 // here recursively. This will happen if, for example, a control
63 // reflects wheel scroll messages to its parent. Bail out if we got
64 // here recursively.
65 static bool recursion_break = false;
66 if (recursion_break)
67 return false;
68 // Check if this window's class has a bad interaction with rerouting.
69 if (!IsCompatibleWithMouseWheelRedirection(window))
70 return false;
71
72 DWORD current_process = GetCurrentProcessId();
73 POINT wheel_location = { GET_X_LPARAM(l_param), GET_Y_LPARAM(l_param) };
74 HWND window_under_wheel = WindowFromPoint(wheel_location);
75
76 if (!CanRedirectMouseWheelFrom(window_under_wheel))
77 return false;
78
79 // Find the lowest Chrome window in the hierarchy that can be the
80 // target of mouse wheel redirection.
81 while (window != window_under_wheel) {
82 // If window_under_wheel is not a valid Chrome window, then return true to
83 // suppress further processing of the message.
84 if (!::IsWindow(window_under_wheel))
85 return true;
86 DWORD wheel_window_process = 0;
87 GetWindowThreadProcessId(window_under_wheel, &wheel_window_process);
88 if (current_process != wheel_window_process) {
89 if (IsChild(window, window_under_wheel)) {
90 // If this message is reflected from a child window in a different
91 // process (happens with out of process windowed plugins) then
92 // we don't want to reroute the wheel message.
93 return false;
94 } else {
95 // The wheel is scrolling over an unrelated window. Make sure that we
96 // have marked that window as supporting mouse wheel rerouting.
97 // Otherwise, we cannot send random WM_MOUSEWHEEL messages to arbitrary
98 // windows. So just drop the message.
99 if (!WindowSupportsRerouteMouseWheel(window_under_wheel))
100 return true;
101 }
102 }
103
104 // window_under_wheel is a Chrome window. If allowed, redirect.
105 if (IsCompatibleWithMouseWheelRedirection(window_under_wheel)) {
106 base::AutoReset<bool> auto_reset_recursion_break(&recursion_break, true);
107 SendMessage(window_under_wheel, WM_MOUSEWHEEL, w_param, l_param);
108 return true;
109 }
110 // If redirection is disallowed, try the parent.
111 window_under_wheel = GetAncestor(window_under_wheel, GA_PARENT);
112 }
113 // If we traversed back to the starting point, we should process
114 // this message normally; return false.
115 return false;
116 }
117
118 } // namespace ui
119