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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 
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_EXPORT WinProcExceptionFilter SetWinProcExceptionFilter(
32     WinProcExceptionFilter filter);
33 
34 // Calls the registered exception filter.
35 BASE_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.
40 BASE_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 //
71 template <WNDPROC proc>
WrappedWindowProc(HWND hwnd,UINT message,WPARAM wparam,LPARAM lparam)72 LRESULT 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