1// Copyright (c) 2012 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
13#include <windows.h>
14
15#include "base/base_export.h"
16#include "base/strings/string16.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_EXPORT WinProcExceptionFilter SetWinProcExceptionFilter(
32    WinProcExceptionFilter filter);
33
34// Calls the registered exception filter.
35BASE_EXPORT int CallExceptionFilter(EXCEPTION_POINTERS* info);
36
37// Initializes the WNDCLASSEX structure |*class_out| to be passed to
38// RegisterClassEx() making sure that it is associated with the module
39// containing the window procedure.
40BASE_EXPORT void InitializeWindowClass(
41    const char16* class_name,
42    WNDPROC window_proc,
43    UINT style,
44    int class_extra,
45    int window_extra,
46    HCURSOR cursor,
47    HBRUSH background,
48    const char16* menu_name,
49    HICON large_icon,
50    HICON small_icon,
51    WNDCLASSEX* class_out);
52
53// Wrapper that supplies a standard exception frame for the provided WindowProc.
54// The normal usage is something like this:
55//
56// LRESULT CALLBACK MyWinProc(HWND hwnd, UINT message,
57//                            WPARAM wparam, LPARAM lparam) {
58//   // Do Something.
59// }
60//
61// ...
62//
63//   WNDCLASSEX wc = {0};
64//   wc.lpfnWndProc = WrappedWindowProc<MyWinProc>;
65//   wc.lpszClassName = class_name;
66//   ...
67//   RegisterClassEx(&wc);
68//
69//   CreateWindowW(class_name, window_name, ...
70//
71template <WNDPROC proc>
72LRESULT CALLBACK WrappedWindowProc(HWND hwnd, UINT message,
73                                   WPARAM wparam, LPARAM lparam) {
74  LRESULT rv = 0;
75  __try {
76    rv = proc(hwnd, message, wparam, lparam);
77  } __except(CallExceptionFilter(GetExceptionInformation())) {
78  }
79  return rv;
80}
81
82}  // namespace win
83}  // namespace base
84
85#endif  // BASE_WIN_WRAPPED_WINDOW_PROC_H_
86