kc3-lang/SDL/src/video/windows/SDL_windowswindow.c

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• Hash : d44f3922
  Author :
  Date : 2014-07-07T10:33:32
  

  Fixed bug 2629 - Mac: crash when calling SDL_DestroyWindow with an active OpenGL context Alex Szpakowski Since this commit https://hg.libsdl.org/SDL/rev/59b543340d63 , calling SDL_DestroyWindow will crash the program if the window has an active OpenGL context. This is because the Cocoa_DestroyWindow code sets the window's driverdata to NULL and then calls [context setWindow:NULL], which tries to access the window's driverdata, resulting in a null pointer dereference. I have attached a patch which fixes the issue by moving the line which sets the driverdata to NULL to after the lines which call functions that use the driverdata pointer.

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• src/video/windows/SDL_windowswindow.c

• /*
    Simple DirectMedia Layer
    Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
  
    This software is provided 'as-is', without any express or implied
    warranty.  In no event will the authors be held liable for any damages
    arising from the use of this software.
  
    Permission is granted to anyone to use this software for any purpose,
    including commercial applications, and to alter it and redistribute it
    freely, subject to the following restrictions:
  
    1. The origin of this software must not be misrepresented; you must not
       claim that you wrote the original software. If you use this software
       in a product, an acknowledgment in the product documentation would be
       appreciated but is not required.
    2. Altered source versions must be plainly marked as such, and must not be
       misrepresented as being the original software.
    3. This notice may not be removed or altered from any source distribution.
  */
  #include "../../SDL_internal.h"
  
  #if SDL_VIDEO_DRIVER_WINDOWS
  
  #include "../../core/windows/SDL_windows.h"
  
  #include "SDL_assert.h"
  #include "../SDL_sysvideo.h"
  #include "../SDL_pixels_c.h"
  #include "../../events/SDL_keyboard_c.h"
  #include "../../events/SDL_mouse_c.h"
  
  #include "SDL_windowsvideo.h"
  #include "SDL_windowswindow.h"
  #include "SDL_hints.h"
  
  /* Dropfile support */
  #include <shellapi.h>
  
  /* This is included after SDL_windowsvideo.h, which includes windows.h */
  #include "SDL_syswm.h"
  
  /* Windows CE compatibility */
  #ifndef SWP_NOCOPYBITS
  #define SWP_NOCOPYBITS 0
  #endif
  
  /* Fake window to help with DirectInput events. */
  HWND SDL_HelperWindow = NULL;
  static WCHAR *SDL_HelperWindowClassName = TEXT("SDLHelperWindowInputCatcher");
  static WCHAR *SDL_HelperWindowName = TEXT("SDLHelperWindowInputMsgWindow");
  static ATOM SDL_HelperWindowClass = 0;
  
  #define STYLE_BASIC         (WS_CLIPSIBLINGS | WS_CLIPCHILDREN)
  #define STYLE_FULLSCREEN    (WS_POPUP)
  #define STYLE_BORDERLESS    (WS_POPUP)
  #define STYLE_NORMAL        (WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_MINIMIZEBOX)
  #define STYLE_RESIZABLE     (WS_THICKFRAME | WS_MAXIMIZEBOX)
  #define STYLE_MASK          (STYLE_FULLSCREEN | STYLE_BORDERLESS | STYLE_NORMAL | STYLE_RESIZABLE)
  
  static DWORD
  GetWindowStyle(SDL_Window * window)
  {
      DWORD style = 0;
  
      if (window->flags & SDL_WINDOW_FULLSCREEN) {
          style |= STYLE_FULLSCREEN;
      } else {
          if (window->flags & SDL_WINDOW_BORDERLESS) {
              style |= STYLE_BORDERLESS;
          } else {
              style |= STYLE_NORMAL;
          }
          if (window->flags & SDL_WINDOW_RESIZABLE) {
              style |= STYLE_RESIZABLE;
          }
      }
      return style;
  }
  
  static void
  WIN_SetWindowPositionInternal(_THIS, SDL_Window * window, UINT flags)
  {
      SDL_WindowData *data = (SDL_WindowData *)window->driverdata;
      HWND hwnd = data->hwnd;
      RECT rect;
      DWORD style;
      HWND top;
      BOOL menu;
      int x, y;
      int w, h;
  
      /* Figure out what the window area will be */
      if (SDL_ShouldAllowTopmost() && (window->flags & (SDL_WINDOW_FULLSCREEN|SDL_WINDOW_INPUT_FOCUS)) == (SDL_WINDOW_FULLSCREEN|SDL_WINDOW_INPUT_FOCUS)) {
          top = HWND_TOPMOST;
      } else {
          top = HWND_NOTOPMOST;
      }
      style = GetWindowLong(hwnd, GWL_STYLE);
      rect.left = 0;
      rect.top = 0;
      rect.right = window->w;
      rect.bottom = window->h;
      menu = (style & WS_CHILDWINDOW) ? FALSE : (GetMenu(hwnd) != NULL);
      AdjustWindowRectEx(&rect, style, menu, 0);
      w = (rect.right - rect.left);
      h = (rect.bottom - rect.top);
      x = window->x + rect.left;
      y = window->y + rect.top;
  
      data->expected_resize = SDL_TRUE;
      SetWindowPos( hwnd, top, x, y, w, h, flags );
      data->expected_resize = SDL_FALSE;
  }
  
  static int
  SetupWindowData(_THIS, SDL_Window * window, HWND hwnd, SDL_bool created)
  {
      SDL_VideoData *videodata = (SDL_VideoData *) _this->driverdata;
      SDL_WindowData *data;
  
      /* Allocate the window data */
      data = (SDL_WindowData *) SDL_calloc(1, sizeof(*data));
      if (!data) {
          return SDL_OutOfMemory();
      }
      data->window = window;
      data->hwnd = hwnd;
      data->hdc = GetDC(hwnd);
      data->created = created;
      data->mouse_button_flags = 0;
      data->videodata = videodata;
  
      window->driverdata = data;
  
      /* Associate the data with the window */
      if (!SetProp(hwnd, TEXT("SDL_WindowData"), data)) {
          ReleaseDC(hwnd, data->hdc);
          SDL_free(data);
          return WIN_SetError("SetProp() failed");
      }
  
      /* Set up the window proc function */
  #ifdef GWLP_WNDPROC
      data->wndproc = (WNDPROC) GetWindowLongPtr(hwnd, GWLP_WNDPROC);
      if (data->wndproc == WIN_WindowProc) {
          data->wndproc = NULL;
      } else {
          SetWindowLongPtr(hwnd, GWLP_WNDPROC, (LONG_PTR) WIN_WindowProc);
      }
  #else
      data->wndproc = (WNDPROC) GetWindowLong(hwnd, GWL_WNDPROC);
      if (data->wndproc == WIN_WindowProc) {
          data->wndproc = NULL;
      } else {
          SetWindowLong(hwnd, GWL_WNDPROC, (LONG_PTR) WIN_WindowProc);
      }
  #endif
  
      /* Fill in the SDL window with the window data */
      {
          RECT rect;
          if (GetClientRect(hwnd, &rect)) {
              int w = rect.right;
              int h = rect.bottom;
              if ((window->w && window->w != w) || (window->h && window->h != h)) {
                  /* We tried to create a window larger than the desktop and Windows didn't allow it.  Override! */
                  WIN_SetWindowPositionInternal(_this, window, SWP_NOCOPYBITS | SWP_NOZORDER | SWP_NOACTIVATE);
              } else {
                  window->w = w;
                  window->h = h;
              }
          }
      }
      {
          POINT point;
          point.x = 0;
          point.y = 0;
          if (ClientToScreen(hwnd, &point)) {
              window->x = point.x;
              window->y = point.y;
          }
      }
      {
          DWORD style = GetWindowLong(hwnd, GWL_STYLE);
          if (style & WS_VISIBLE) {
              window->flags |= SDL_WINDOW_SHOWN;
          } else {
              window->flags &= ~SDL_WINDOW_SHOWN;
          }
          if (style & (WS_BORDER | WS_THICKFRAME)) {
              window->flags &= ~SDL_WINDOW_BORDERLESS;
          } else {
              window->flags |= SDL_WINDOW_BORDERLESS;
          }
          if (style & WS_THICKFRAME) {
              window->flags |= SDL_WINDOW_RESIZABLE;
          } else {
              window->flags &= ~SDL_WINDOW_RESIZABLE;
          }
  #ifdef WS_MAXIMIZE
          if (style & WS_MAXIMIZE) {
              window->flags |= SDL_WINDOW_MAXIMIZED;
          } else
  #endif
          {
              window->flags &= ~SDL_WINDOW_MAXIMIZED;
          }
  #ifdef WS_MINIMIZE
          if (style & WS_MINIMIZE) {
              window->flags |= SDL_WINDOW_MINIMIZED;
          } else
  #endif
          {
              window->flags &= ~SDL_WINDOW_MINIMIZED;
          }
      }
      if (GetFocus() == hwnd) {
          window->flags |= SDL_WINDOW_INPUT_FOCUS;
          SDL_SetKeyboardFocus(data->window);
  
          if (window->flags & SDL_WINDOW_INPUT_GRABBED) {
              RECT rect;
              GetClientRect(hwnd, &rect);
              ClientToScreen(hwnd, (LPPOINT) & rect);
              ClientToScreen(hwnd, (LPPOINT) & rect + 1);
              ClipCursor(&rect);
          }
      }
  
      /* Enable multi-touch */
      if (videodata->RegisterTouchWindow) {
          videodata->RegisterTouchWindow(hwnd, (TWF_FINETOUCH|TWF_WANTPALM));
      }
  
      /* Enable dropping files */
      DragAcceptFiles(hwnd, TRUE);
  
      /* All done! */
      return 0;
  }
  
  int
  WIN_CreateWindow(_THIS, SDL_Window * window)
  {
      HWND hwnd;
      RECT rect;
      DWORD style = STYLE_BASIC;
      int x, y;
      int w, h;
  
      style |= GetWindowStyle(window);
  
      /* Figure out what the window area will be */
      rect.left = window->x;
      rect.top = window->y;
      rect.right = window->x + window->w;
      rect.bottom = window->y + window->h;
      AdjustWindowRectEx(&rect, style, FALSE, 0);
      x = rect.left;
      y = rect.top;
      w = (rect.right - rect.left);
      h = (rect.bottom - rect.top);
  
      hwnd =
          CreateWindow(SDL_Appname, TEXT(""), style, x, y, w, h, NULL, NULL,
                       SDL_Instance, NULL);
      if (!hwnd) {
          return WIN_SetError("Couldn't create window");
      }
  
      WIN_PumpEvents(_this);
  
      if (SetupWindowData(_this, window, hwnd, SDL_TRUE) < 0) {
          DestroyWindow(hwnd);
          return -1;
      }
  
  #if SDL_VIDEO_OPENGL_WGL
      /* We need to initialize the extensions before deciding how to create ES profiles */
      if (window->flags & SDL_WINDOW_OPENGL) {
          WIN_GL_InitExtensions(_this);
      }
  #endif
  
  #if SDL_VIDEO_OPENGL_ES2
      if ((window->flags & SDL_WINDOW_OPENGL) &&
          _this->gl_config.profile_mask == SDL_GL_CONTEXT_PROFILE_ES
  #if SDL_VIDEO_OPENGL_WGL           
          && (!_this->gl_data || !_this->gl_data->HAS_WGL_EXT_create_context_es2_profile)
  #endif  
          ) {
  #if SDL_VIDEO_OPENGL_EGL  
          if (WIN_GLES_SetupWindow(_this, window) < 0) {
              WIN_DestroyWindow(_this, window);
              return -1;
          }
  #else
          return SDL_SetError("Could not create GLES window surface (no EGL support available)");
  #endif /* SDL_VIDEO_OPENGL_EGL */
      } else 
  #endif /* SDL_VIDEO_OPENGL_ES2 */
  
  #if SDL_VIDEO_OPENGL_WGL
      if (window->flags & SDL_WINDOW_OPENGL) {
          if (WIN_GL_SetupWindow(_this, window) < 0) {
              WIN_DestroyWindow(_this, window);
              return -1;
          }
      }
  #endif
  
      return 0;
  }
  
  int
  WIN_CreateWindowFrom(_THIS, SDL_Window * window, const void *data)
  {
      HWND hwnd = (HWND) data;
      LPTSTR title;
      int titleLen;
  
      /* Query the title from the existing window */
      titleLen = GetWindowTextLength(hwnd);
      title = SDL_stack_alloc(TCHAR, titleLen + 1);
      if (title) {
          titleLen = GetWindowText(hwnd, title, titleLen);
      } else {
          titleLen = 0;
      }
      if (titleLen > 0) {
          window->title = WIN_StringToUTF8(title);
      }
      if (title) {
          SDL_stack_free(title);
      }
  
      if (SetupWindowData(_this, window, hwnd, SDL_FALSE) < 0) {
          return -1;
      }
  
  #if SDL_VIDEO_OPENGL_WGL
      {
          const char *hint = SDL_GetHint(SDL_HINT_VIDEO_WINDOW_SHARE_PIXEL_FORMAT);
          if (hint) {
              /* This hint is a pointer (in string form) of the address of
                 the window to share a pixel format with
              */
              SDL_Window *otherWindow = NULL;
              SDL_sscanf(hint, "%p", (void**)&otherWindow);
  
              /* Do some error checking on the pointer */
              if (otherWindow != NULL && otherWindow->magic == &_this->window_magic)
              {
                  /* If the otherWindow has SDL_WINDOW_OPENGL set, set it for the new window as well */
                  if (otherWindow->flags & SDL_WINDOW_OPENGL)
                  {
                      window->flags |= SDL_WINDOW_OPENGL;
                      if(!WIN_GL_SetPixelFormatFrom(_this, otherWindow, window)) {
                          return -1;
                      }
                  }
              }
          }
      }
  #endif
      return 0;
  }
  
  void
  WIN_SetWindowTitle(_THIS, SDL_Window * window)
  {
      HWND hwnd = ((SDL_WindowData *) window->driverdata)->hwnd;
      LPTSTR title;
  
      if (window->title) {
          title = WIN_UTF8ToString(window->title);
      } else {
          title = NULL;
      }
      SetWindowText(hwnd, title ? title : TEXT(""));
      SDL_free(title);
  }
  
  void
  WIN_SetWindowIcon(_THIS, SDL_Window * window, SDL_Surface * icon)
  {
      HWND hwnd = ((SDL_WindowData *) window->driverdata)->hwnd;
      HICON hicon = NULL;
      BYTE *icon_bmp;
      int icon_len, y;
      SDL_RWops *dst;
  
      /* Create temporary bitmap buffer */
      icon_len = 40 + icon->h * icon->w * 4;
      icon_bmp = SDL_stack_alloc(BYTE, icon_len);
      dst = SDL_RWFromMem(icon_bmp, icon_len);
      if (!dst) {
          SDL_stack_free(icon_bmp);
          return;
      }
  
      /* Write the BITMAPINFO header */
      SDL_WriteLE32(dst, 40);
      SDL_WriteLE32(dst, icon->w);
      SDL_WriteLE32(dst, icon->h * 2);
      SDL_WriteLE16(dst, 1);
      SDL_WriteLE16(dst, 32);
      SDL_WriteLE32(dst, BI_RGB);
      SDL_WriteLE32(dst, icon->h * icon->w * 4);
      SDL_WriteLE32(dst, 0);
      SDL_WriteLE32(dst, 0);
      SDL_WriteLE32(dst, 0);
      SDL_WriteLE32(dst, 0);
  
      /* Write the pixels upside down into the bitmap buffer */
      SDL_assert(icon->format->format == SDL_PIXELFORMAT_ARGB8888);
      y = icon->h;
      while (y--) {
          Uint8 *src = (Uint8 *) icon->pixels + y * icon->pitch;
          SDL_RWwrite(dst, src, icon->pitch, 1);
      }
  
      hicon = CreateIconFromResource(icon_bmp, icon_len, TRUE, 0x00030000);
  
      SDL_RWclose(dst);
      SDL_stack_free(icon_bmp);
  
      /* Set the icon for the window */
      SendMessage(hwnd, WM_SETICON, ICON_SMALL, (LPARAM) hicon);
  
      /* Set the icon in the task manager (should we do this?) */
      SendMessage(hwnd, WM_SETICON, ICON_BIG, (LPARAM) hicon);
  }
  
  void
  WIN_SetWindowPosition(_THIS, SDL_Window * window)
  {
      WIN_SetWindowPositionInternal(_this, window, SWP_NOCOPYBITS | SWP_NOSIZE | SWP_NOACTIVATE);
  }
  
  void
  WIN_SetWindowSize(_THIS, SDL_Window * window)
  {
      WIN_SetWindowPositionInternal(_this, window, SWP_NOCOPYBITS | SWP_NOMOVE | SWP_NOACTIVATE);
  }
  
  void
  WIN_ShowWindow(_THIS, SDL_Window * window)
  {
      HWND hwnd = ((SDL_WindowData *) window->driverdata)->hwnd;
      ShowWindow(hwnd, SW_SHOW);
  }
  
  void
  WIN_HideWindow(_THIS, SDL_Window * window)
  {
      HWND hwnd = ((SDL_WindowData *) window->driverdata)->hwnd;
      ShowWindow(hwnd, SW_HIDE);
  }
  
  void
  WIN_RaiseWindow(_THIS, SDL_Window * window)
  {
      WIN_SetWindowPositionInternal(_this, window, SWP_NOCOPYBITS | SWP_NOMOVE | SWP_NOSIZE);
  }
  
  void
  WIN_MaximizeWindow(_THIS, SDL_Window * window)
  {
      SDL_WindowData *data = (SDL_WindowData *)window->driverdata;
      HWND hwnd = data->hwnd;
      data->expected_resize = SDL_TRUE;
      ShowWindow(hwnd, SW_MAXIMIZE);
      data->expected_resize = SDL_FALSE;
  }
  
  void
  WIN_MinimizeWindow(_THIS, SDL_Window * window)
  {
      HWND hwnd = ((SDL_WindowData *) window->driverdata)->hwnd;
      ShowWindow(hwnd, SW_MINIMIZE);
  }
  
  void
  WIN_SetWindowBordered(_THIS, SDL_Window * window, SDL_bool bordered)
  {
      SDL_WindowData *data = (SDL_WindowData *)window->driverdata;
      HWND hwnd = data->hwnd;
      DWORD style = GetWindowLong(hwnd, GWL_STYLE);
  
      if (bordered) {
          style &= ~STYLE_BORDERLESS;
          style |= STYLE_NORMAL;
      } else {
          style &= ~STYLE_NORMAL;
          style |= STYLE_BORDERLESS;
      }
  
      data->in_border_change = SDL_TRUE;
      SetWindowLong( hwnd, GWL_STYLE, style );
      WIN_SetWindowPositionInternal(_this, window, SWP_NOCOPYBITS | SWP_FRAMECHANGED | SWP_NOZORDER | SWP_NOACTIVATE);
      data->in_border_change = SDL_FALSE;
  }
  
  void
  WIN_RestoreWindow(_THIS, SDL_Window * window)
  {
      SDL_WindowData *data = (SDL_WindowData *)window->driverdata;
      HWND hwnd = data->hwnd;
      data->expected_resize = SDL_TRUE;
      ShowWindow(hwnd, SW_RESTORE);
      data->expected_resize = SDL_FALSE;
  }
  
  void
  WIN_SetWindowFullscreen(_THIS, SDL_Window * window, SDL_VideoDisplay * display, SDL_bool fullscreen)
  {
      SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
      HWND hwnd = data->hwnd;
      RECT rect;
      SDL_Rect bounds;
      DWORD style;
      HWND top;
      BOOL menu;
      int x, y;
      int w, h;
  
      if (SDL_ShouldAllowTopmost() && (window->flags & (SDL_WINDOW_FULLSCREEN|SDL_WINDOW_INPUT_FOCUS)) == (SDL_WINDOW_FULLSCREEN|SDL_WINDOW_INPUT_FOCUS)) {
          top = HWND_TOPMOST;
      } else {
          top = HWND_NOTOPMOST;
      }
  
      style = GetWindowLong(hwnd, GWL_STYLE);
      style &= ~STYLE_MASK;
      style |= GetWindowStyle(window);
  
      WIN_GetDisplayBounds(_this, display, &bounds);
  
      if (fullscreen) {
          x = bounds.x;
          y = bounds.y;
          w = bounds.w;
          h = bounds.h;
      } else {
          rect.left = 0;
          rect.top = 0;
          rect.right = window->windowed.w;
          rect.bottom = window->windowed.h;
          menu = (style & WS_CHILDWINDOW) ? FALSE : (GetMenu(hwnd) != NULL);
          AdjustWindowRectEx(&rect, style, menu, 0);
          w = (rect.right - rect.left);
          h = (rect.bottom - rect.top);
          x = window->windowed.x + rect.left;
          y = window->windowed.y + rect.top;
      }
      SetWindowLong(hwnd, GWL_STYLE, style);
      data->expected_resize = SDL_TRUE;
      SetWindowPos(hwnd, top, x, y, w, h, SWP_NOCOPYBITS | SWP_NOACTIVATE);
      data->expected_resize = SDL_FALSE;
  }
  
  int
  WIN_SetWindowGammaRamp(_THIS, SDL_Window * window, const Uint16 * ramp)
  {
      SDL_VideoDisplay *display = SDL_GetDisplayForWindow(window);
      SDL_DisplayData *data = (SDL_DisplayData *) display->driverdata;
      HDC hdc;
      BOOL succeeded = FALSE;
  
      hdc = CreateDC(data->DeviceName, NULL, NULL, NULL);
      if (hdc) {
          succeeded = SetDeviceGammaRamp(hdc, (LPVOID)ramp);
          if (!succeeded) {
              WIN_SetError("SetDeviceGammaRamp()");
          }
          DeleteDC(hdc);
      }
      return succeeded ? 0 : -1;
  }
  
  int
  WIN_GetWindowGammaRamp(_THIS, SDL_Window * window, Uint16 * ramp)
  {
      SDL_VideoDisplay *display = SDL_GetDisplayForWindow(window);
      SDL_DisplayData *data = (SDL_DisplayData *) display->driverdata;
      HDC hdc;
      BOOL succeeded = FALSE;
  
      hdc = CreateDC(data->DeviceName, NULL, NULL, NULL);
      if (hdc) {
          succeeded = GetDeviceGammaRamp(hdc, (LPVOID)ramp);
          if (!succeeded) {
              WIN_SetError("GetDeviceGammaRamp()");
          }
          DeleteDC(hdc);
      }
      return succeeded ? 0 : -1;
  }
  
  void
  WIN_SetWindowGrab(_THIS, SDL_Window * window, SDL_bool grabbed)
  {
      WIN_UpdateClipCursor(window);
  
      if (window->flags & SDL_WINDOW_FULLSCREEN) {
          UINT flags = SWP_NOCOPYBITS | SWP_NOMOVE | SWP_NOSIZE;
  
          if (!(window->flags & SDL_WINDOW_SHOWN)) {
              flags |= SWP_NOACTIVATE;
          }
          WIN_SetWindowPositionInternal(_this, window, flags);
      }
  }
  
  void
  WIN_DestroyWindow(_THIS, SDL_Window * window)
  {
      SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
  
      if (data) {
          ReleaseDC(data->hwnd, data->hdc);
          if (data->created) {
              DestroyWindow(data->hwnd);
          } else {
              /* Restore any original event handler... */
              if (data->wndproc != NULL) {
  #ifdef GWLP_WNDPROC
                  SetWindowLongPtr(data->hwnd, GWLP_WNDPROC,
                                   (LONG_PTR) data->wndproc);
  #else
                  SetWindowLong(data->hwnd, GWL_WNDPROC,
                                (LONG_PTR) data->wndproc);
  #endif
              }
          }
          SDL_free(data);
      }
      window->driverdata = NULL;
  }
  
  SDL_bool
  WIN_GetWindowWMInfo(_THIS, SDL_Window * window, SDL_SysWMinfo * info)
  {
      HWND hwnd = ((SDL_WindowData *) window->driverdata)->hwnd;
      if (info->version.major <= SDL_MAJOR_VERSION) {
          info->subsystem = SDL_SYSWM_WINDOWS;
          info->info.win.window = hwnd;
          return SDL_TRUE;
      } else {
          SDL_SetError("Application not compiled with SDL %d.%d\n",
                       SDL_MAJOR_VERSION, SDL_MINOR_VERSION);
          return SDL_FALSE;
      }
  }
  
  
  /*
   * Creates a HelperWindow used for DirectInput events.
   */
  int
  SDL_HelperWindowCreate(void)
  {
      HINSTANCE hInstance = GetModuleHandle(NULL);
      WNDCLASS wce;
  
      /* Make sure window isn't created twice. */
      if (SDL_HelperWindow != NULL) {
          return 0;
      }
  
      /* Create the class. */
      SDL_zero(wce);
      wce.lpfnWndProc = DefWindowProc;
      wce.lpszClassName = (LPCWSTR) SDL_HelperWindowClassName;
      wce.hInstance = hInstance;
  
      /* Register the class. */
      SDL_HelperWindowClass = RegisterClass(&wce);
      if (SDL_HelperWindowClass == 0 && GetLastError() != ERROR_CLASS_ALREADY_EXISTS) {
          return WIN_SetError("Unable to create Helper Window Class");
      }
  
      /* Create the window. */
      SDL_HelperWindow = CreateWindowEx(0, SDL_HelperWindowClassName,
                                        SDL_HelperWindowName,
                                        WS_OVERLAPPED, CW_USEDEFAULT,
                                        CW_USEDEFAULT, CW_USEDEFAULT,
                                        CW_USEDEFAULT, HWND_MESSAGE, NULL,
                                        hInstance, NULL);
      if (SDL_HelperWindow == NULL) {
          UnregisterClass(SDL_HelperWindowClassName, hInstance);
          return WIN_SetError("Unable to create Helper Window");
      }
  
      return 0;
  }
  
  
  /*
   * Destroys the HelperWindow previously created with SDL_HelperWindowCreate.
   */
  void
  SDL_HelperWindowDestroy(void)
  {
      HINSTANCE hInstance = GetModuleHandle(NULL);
  
      /* Destroy the window. */
      if (SDL_HelperWindow != NULL) {
          if (DestroyWindow(SDL_HelperWindow) == 0) {
              WIN_SetError("Unable to destroy Helper Window");
              return;
          }
          SDL_HelperWindow = NULL;
      }
  
      /* Unregister the class. */
      if (SDL_HelperWindowClass != 0) {
          if ((UnregisterClass(SDL_HelperWindowClassName, hInstance)) == 0) {
              WIN_SetError("Unable to destroy Helper Window Class");
              return;
          }
          SDL_HelperWindowClass = 0;
      }
  }
  
  void WIN_OnWindowEnter(_THIS, SDL_Window * window)
  {
  #ifdef WM_MOUSELEAVE
      SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
      TRACKMOUSEEVENT trackMouseEvent;
  
      if (!data || !data->hwnd) {
          /* The window wasn't fully initialized */
          return;
      }
  
      trackMouseEvent.cbSize = sizeof(TRACKMOUSEEVENT);
      trackMouseEvent.dwFlags = TME_LEAVE;
      trackMouseEvent.hwndTrack = data->hwnd;
  
      TrackMouseEvent(&trackMouseEvent);
  #endif /* WM_MOUSELEAVE */
  }
  
  void
  WIN_UpdateClipCursor(SDL_Window *window)
  {
      SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
      SDL_Mouse *mouse = SDL_GetMouse();
  
      if (data->focus_click_pending) {
          return;
      }
  
      if ((mouse->relative_mode || (window->flags & SDL_WINDOW_INPUT_GRABBED)) &&
          (window->flags & SDL_WINDOW_INPUT_FOCUS)) {
          if (mouse->relative_mode && !mouse->relative_mode_warp) {
              LONG cx, cy;
              RECT rect;
              GetWindowRect(data->hwnd, &rect);
  
              cx = (rect.left + rect.right) / 2;
              cy = (rect.top + rect.bottom) / 2;
  
              /* Make an absurdly small clip rect */
              rect.left = cx - 1;
              rect.right = cx + 1;
              rect.top = cy - 1;
              rect.bottom = cy + 1;
  
              ClipCursor(&rect);
          } else {
              RECT rect;
              if (GetClientRect(data->hwnd, &rect) && !IsRectEmpty(&rect)) {
                  ClientToScreen(data->hwnd, (LPPOINT) & rect);
                  ClientToScreen(data->hwnd, (LPPOINT) & rect + 1);
                  ClipCursor(&rect);
              }
          }
      } else {
          ClipCursor(NULL);
      }
  }
  
  int
  WIN_SetWindowHitTest(SDL_Window *window, SDL_bool enabled)
  {
      return 0;  /* just succeed, the real work is done elsewhere. */
  }
  
  #endif /* SDL_VIDEO_DRIVER_WINDOWS */
  
  /* vi: set ts=4 sw=4 expandtab: */
  

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