base/win/wrapped_window_proc.h

   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>
  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_