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
18namespace base {
19namespace 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.
26typedef 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.
31BASE_API WinProcExceptionFilter SetWinProcExceptionFilter(
32    WinProcExceptionFilter filter);
33
34// Calls the registered exception filter.
35BASE_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//
55template <WNDPROC proc>
56LRESULT 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