Thread: DialogBox and BITMAPS

Hi

Im trying to load a BMP onto a DialogBox, but it never displays...

heres my code:

In my resource.rc file i have this:

Code:

IDB_WALLS BITMAP "wall.bmp"

IDD_TESTBMP DIALOGEX 225, 200, 486, 313
STYLE DS_MODALFRAME | WS_POPUP | WS_CAPTION | WS_SYSMENU
CAPTION "Cell:"
FONT 8, "MS Sans Serif"
BEGIN
    DEFPUSHBUTTON   "OK",IDOK,429,7,50,14
    CONTROL         "",IDB_WALLS,"Static",SS_BITMAP,0,0,305,278
END

In my Resource.h file i have the following:

Code:

#define IDB_WALLS 501

Code:

case WM_INITDIALOG:
        {
           hDC = BeginPaint(hWnd, &Ps);

           walls = LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_WALLS));
           if(walls == NULL)
                MessageBox(hwnd, "Could not load Bitmap!", "Error", MB_OK | MB_ICONEXCLAMATION);
           break;
           
           MemDC = CreateCompatibleDC(hDC);
           SelectObject(MemDC, walls);
           //Works?
           BitBlt(hDC, 0, 0, 305, 278, MemDC, 0, 0, SRCCOPY);
           DeleteDC(MemDC);
	       DeleteObject(walls);

           return TRUE;
        }

Now the dimensions of the BMP are 305x278, and im unsure the BitBlt() function call has the correct parameters? Im sure its something like im drawing on the wrong portion of the DialogBox? Ive also checked the file is in the correct directory also, and im using DevC++ / WinXP

Any help appreciated greatly !

Firstly, do your drawing in your WM_PAINT handler and not WM_INITDIALOG as you seem to be doing. Secondly, don't delete a dc that hasn't been restored to its original state. Rewriting what you have to reflect these points:

Code:

case WM_INITDIALOG:
  {
  walls = LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_WALLS));
  if(walls == NULL)
    MessageBox(hwnd, "Could not load Bitmap!", "Error", MB_OK | MB_ICONEXCLAMATION);
  return TRUE;
  }
case WM_PAINT:
  {
  HBITMAP     hOrig;
  HDC         MemDC;
  PAINTSTRUCT ps;

  BeginPaint(hwnd,&ps);
    MemDC = CreateCompatibleDC(hDC);
    hOrig=(HBITMAP)SelectObject(MemDC,walls);
    BitBlt(ps.hdc, 0, 0, 305, 278, MemDC, 0, 0, SRCCOPY);
  EndPaint(hwnd,&ps);
  /*restore and clean up gdi resources*/
  SelectObject(MemDC,hOrig);
  DeleteDC(MemDC);
  return 0;
  }
case WM_DESTROY:
  DeleteObject(walls); 
  return 0;
}

If you're unsure about parameters for api functions then check them up on msdn.

edit: corrected BitBlt first parameter.

Sorry, I didn't use the return value from BeginPaint as you had in your original example as the first parameter to BitBlt; it's fixed now (the hdc parameter of the PAINTSTRUCT is the same as the dc handle returned by BeginPaint).

If that still fails to work then check the return value from LoadBitmap and ensure it's non-NULL. If it is NULL then use GetLastError to try and get some sort of idea of why it's failing.