1 // Copyright (c) 2011 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 // Provides a way to handle exceptions that happen while a WindowProc is
6 // running. The behavior of exceptions generated inside a WindowProc is OS
7 // dependent, but it is possible that the OS just ignores the exception and
8 // continues execution, which leads to unpredictable behavior for Chrome.
9
10 #ifndef BASE_WIN_WRAPPED_WINDOW_PROC_H_
11 #define BASE_WIN_WRAPPED_WINDOW_PROC_H_
12 #pragma once
13
14 #include <windows.h>
15
16 #include "base/base_api.h"
17
18 namespace base {
19 namespace win {
20
21 // An exception filter for a WindowProc. The return value determines how the
22 // exception should be handled, following standard SEH rules. However, the
23 // expected behavior for this function is to not return, instead of returning
24 // EXCEPTION_EXECUTE_HANDLER or similar, given that in general we are not
25 // prepared to handle exceptions.
26 typedef int (__cdecl *WinProcExceptionFilter)(EXCEPTION_POINTERS* info);
27
28 // Sets the filter to deal with exceptions inside a WindowProc. Returns the old
29 // exception filter, if any.
30 // This function should be called before any window is created.
31 BASE_API WinProcExceptionFilter SetWinProcExceptionFilter(
32 WinProcExceptionFilter filter);
33
34 // Calls the registered exception filter.
35 BASE_API int CallExceptionFilter(EXCEPTION_POINTERS* info);
36
37 // Wrapper that supplies a standard exception frame for the provided WindowProc.
38 // The normal usage is something like this:
39 //
40 // LRESULT CALLBACK MyWinProc(HWND hwnd, UINT message,
41 // WPARAM wparam, LPARAM lparam) {
42 // // Do Something.
43 // }
44 //
45 // ...
46 //
47 // WNDCLASSEX wc = {0};
48 // wc.lpfnWndProc = WrappedWindowProc<MyWinProc>;
49 // wc.lpszClassName = class_name;
50 // ...
51 // RegisterClassEx(&wc);
52 //
53 // CreateWindowW(class_name, window_name, ...
54 //
55 template <WNDPROC proc>
WrappedWindowProc(HWND hwnd,UINT message,WPARAM wparam,LPARAM lparam)56 LRESULT CALLBACK WrappedWindowProc(HWND hwnd, UINT message,
57 WPARAM wparam, LPARAM lparam) {
58 LRESULT rv = 0;
59 __try {
60 rv = proc(hwnd, message, wparam, lparam);
61 } __except(CallExceptionFilter(GetExceptionInformation())) {
62 }
63 return rv;
64 }
65
66 } // namespace win
67 } // namespace base
68
69 #endif // BASE_WIN_WRAPPED_WINDOW_PROC_H_
70