Cant get an image to show on my HDC

This is a discussion on Cant get an image to show on my HDC within the Windows Programming forums, part of the Platform Specific Boards category; I cant seem to get a BITMAP to show on my HDC //globals Code: //Win32 Bitmap stuff HANDLE hImage; HWND ...

  1. #1
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    Cant get an image to show on my HDC

    I cant seem to get a BITMAP to show on my HDC
    //globals
    Code:
    //Win32 Bitmap stuff
    HANDLE hImage;
    HWND button_hWnd;
    HDC hdc;
    HDC c_hdc;
    BITMAP Bitmap;
    SIZE ImageSize;
    Code:
    hImage = LoadImage(hInstance,"Test.bmp",IMAGE_BITMAP,0,0,LR_LOADFROMFILE);
       if(hImage != INVALID_HANDLE_VALUE)
       {
    	   MessageBox(NULL,"Loaded Test.bmp","",0);
       }
       hdc = GetDC(hWnd);
       c_hdc = CreateCompatibleDC(hdc);
       GetObject(c_hdc,sizeof(BITMAP),&Bitmap);
       ImageSize.cx = Bitmap.bmWidth;
       ImageSize.cy = Bitmap.bmHeight;
    in the Wndproc WM_PAINT message

    Code:
    case WM_PAINT:
    		hdc = BeginPaint(hWnd, &ps);
    		SelectObject(c_hdc,hImage);
    		BitBlt(hdc,0,0,ImageSize.cx,ImageSize.cy,c_hdc,0,0,SRCCOPY);
    		// TODO: Add any drawing code here...
    		EndPaint(hWnd, &ps);
    		break;

  2. #2
    and the hat of wrongness Salem's Avatar
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    > hImage = LoadImage(hInstance,"Test.bmp",IMAGE_BITMAP,0,0,LR _LOADFROMFILE);
    But is this done in a different WM_MESSAGE case?

    If so, you need to make things like c_hdc to be static variables, so they're preserved from one call to your winproc to the next.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
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    no its done straight after the main window is created

  4. #4
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    Fixing your error checking, INVALID_HANDLE_VALUE is a backwards compatible value used only with CreateFile. If LoadImage fails, it retuns NULL.

    Also, when you perform SelectObject, you're pushing a 1x1 monochrome bitmap (included free with the memory DC) into the ether. This is bad. Store the return value and put it back before EndPaint.

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