Thread: opening seperate window to display bitmaps

Originally posted by bennyandthejets
Could you post the code that registers the window class "Child_SCTS"?

Code:

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (BLACK_BRUSH) ;
     wndclass.lpszMenuName  = "MENUDEMO" ;
     wndclass.lpszClassName = szAppName ;



     wndclass.lpfnWndProc   = ChildWndProc ;
     wndclass.hIcon 		    = NULL ;
     wndclass.lpszClassName = "Child_SCTS" ;
     wndclass.cbWndExtra    = sizeof (long) ;

Hang on........

Why a child window?
It does not need (or want) to be a child, make it a grown up window!

Code:

//first fix that GDI memory leak
//save the bitmap already in the HDC
hOldBmp=SelectObject (hdcmem, hBitmap);
      for (y = 0 ; y < cyClient ; y += cySource)
      for (x = 0 ; x < cxClient ; x += cxSource)
      {
      	BitBlt (hdc, x, y, cxSource, cySource, hdcmem, 0, 0, SRCCOPY) ;
      }
//Must select old bmp back to delete DC or memory leak 
SelectObject(hOldBmp);
      DeleteDC (hdcmem);

//change the create call
//this is wrong
hwndChild = CreateWindow ("Child_SCTS", TEXT("Wiring diagram"),
               	WS_CHILDWINDOW | WS_VISIBLE, 0, 0, 282, 363, hwnd, MAKEINTRESOURCE("568a"),
                  TEXT("hInstance"), NULL);

//this is correct (but I used a .c file so some stricter casting may apply, I don't know if you used .cpp)

//note the change to the hInstance, style and menu params

hwndChild = CreateWindow ("Child_SCTS", TEXT("Wiring diagram"),
               	WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN | WS_VISIBLE, 0, 0, 282, 363,hWnd,(HMENU) NULL,
                  hInstance, NULL);

//in the create the load image is sightly off, try
hBitmap = LoadBitmap (hInstance,MAKEINTRESOURCE(IDB_568a));

That should work.

EDIT
You do register the class?
if(!RegisterClass(&wndclass))
return FALSE;

Just to be picky/tricky....

try creating the memhdc in the init or create msg.
then create another the size of the dialog (make it global or static)
Draw the image to it as you do in the paint
Delete the small hdc as you do in the paint
Keep the one the same size as the dialog

In the paint you should be able to call GetUpdateRect() (or use the param in the BeginPaint) in your BitBlt() and just draw from your global (or static) hdc. This will be quicker.

On the dialogs close delete the global or static hdc

the next step is to destroy the global or static hdc when the dialog is resized and create it again the correct size, then call a paint. Functions are useful here and keep the callback uncluttered.

Yes I do register the class but I took that out cause I didn't think you needed to see it but:

Code:

     HWND     hwnd ;
     MSG      msg ;
     WNDCLASS wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (BLACK_BRUSH) ;
     wndclass.lpszMenuName  = "MENUDEMO" ;
     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("This program requires Windows NT!"),
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }

     wndclass.lpfnWndProc   = ChildWndProc ;
     wndclass.hIcon 		    = NULL ;
     wndclass.lpszClassName = "Child_SCTS" ;
     wndclass.cbWndExtra    = sizeof (long) ;

     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("This program requires Windows NT!"),
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }

I tried your createwindow command, worked once and the loadbitmap failed. I copied your bitmap line and its giving me

Code:

Error:  scts.c(242,64):Undefined symbol 'IDB_568a'

the line is the load bitmap line.
I readded the quotations around IDB_568a and re compiled now I am back to where I started with createwindow failing. Im starting to remember why I stopped programming.
The new createwindow call is

Code:

               MessageBox (NULL, TEXT  ("The menu works."), TEXT ("Hellomsg")
               	, 0);

                  hwndChild = CreateWindow ("Child_SCTS", TEXT("Wiring diagram"),
                  WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN | WS_VISIBLE, 0, 0, 282, 363,hwnd, NULL,
                  hInstance, NULL);

                  if (hwndChild == NULL) {
     					char buf[256];
     					sprintf(buf, "CreateWindow failed with %d", GetLastError());
     					MessageBoxA(NULL, buf, NULL, 0);
					}
               return 0;

The Load bitmap section is(I haven't fixed the GDI leak yet, fix the problem before causing new ones)

Code:

static HBITMAP  hBitmap;
   static int      cxClient, cyClient, cxSource, cySource ;
   BITMAP          bitmap;
   HDC				 hdc, hdcmem;
   HINSTANCE		 hInstance;
   int 				 x,y;
   PAINTSTRUCT 	 ps;

	switch (message)
   {
   	case WM_CREATE :
      hInstance = ((LPCREATESTRUCT) lParam)->hInstance;

      hBitmap = LoadBitmap (hInstance,MAKEINTRESOURCE(IDB_568a));

      if (hBitmap == NULL) {
     	char buf[256];
     	sprintf(buf, "LoadBitmap failed with %d", GetLastError());
     	MessageBoxA(NULL, buf, NULL, 0);
		}

      GetObject (hBitmap, sizeof (BITMAP), &bitmap);

      cxSource = bitmap.bmWidth;
      cySource = bitmap.bmHeight;

      return 0;

      case WM_PAINT:
      hdc = BeginPaint (hwnd, &ps) ;
      hdcmem = CreateCompatibleDC (hdc) ;
      SelectObject (hdcmem, hBitmap);
      for (y = 0 ; y < cyClient ; y += cySource)
      for (x = 0 ; x < cxClient ; x += cxSource)
      {
      	BitBlt (hdc, x, y, cxSource, cySource, hdcmem, 0, 0, SRCCOPY) ;
      }

      DeleteDC (hdcmem);
      EndPaint (hwnd, &ps);
      return 0;

I hope thats enough code, if not I attached the source code file, resource file and resource header. Its all setup for Borland 5.0 IDE compiler.

You do have a bitmap in your resources with the ID number.

IDB_568a

and have included the resource.h header in this file?

Remember with resource ID numbers;
IDB_568a is not text, to the compiler it is a number.
It is easier for us to tell which is a picture of a brick between IDB_BRICK and 1234 (the int resource ID #define 'd as IDB_BRICK in resource.h)

Where does cyClient and cxClient get a value? (not in the code posted so just checking)
ie
for (y = 0 ; y < cyClient ; y += cySource)
for (x = 0 ; x < cxClient ; x += cxSource)



I copied your code and opened a dlg using it so I know the corrections work.

SO the code works for you?
I have cyClient and cxClient are based on the Hiword and Loword of the WM_SIZE message. its acturally IDB_568A (I just noticed and corrected where I had IDB_568a) but yes I have it in the resource file and the resource.h file. Ive been staring at the code for days and my eyes are starting to see code when I close my eyes.

When this sort of thing happens, I am often forced to start again from scratch, and then the program miraculously works. I have spent hours comparing the working version and the faulty version, and still cant find any differences. It's all good being able to spot errors and debug well, but when it gets to this point, it's useless.

>>SO the code works for you?

Yes. The drawing did not but I did not set the screen dims.

Comment out the drawing bit. Just get the window open.

I did not register the first class only the second.



Instead of the loop to draw the bitmap try

CreatePatternBrush()//with the bitmap
then
FillRect() or Rectangle() //use the one in the paint struct or the whole client

Remember to delete the brush after.

Originally posted by bennyandthejets
When this sort of thing happens, I am often forced to start again from scratch, and then the program miraculously works. I have spent hours comparing the working version and the faulty version, and still cant find any differences. It's all good being able to spot errors and debug well, but when it gets to this point, it's useless.

This is acturally what I decided to do. But I have come to the cocliusion it is something with my compiler. This is because I decided to make it easier and use dialog boxes with static Bitmaps. Although even without the bitmap the Dialog Box call failed. I think for some reason my compiler/computer is having problems with creating second windows in the program.

What is this for?

wndclass.cbWndExtra = sizeof (long) ;

Try without it.

>>I think for some reason my compiler/computer is having problems with creating second windows in the program.

What did getlasterror return?

Use the same wndclass (diff wndproc) and see if that helps.

Use 'break' instead of 'return 0' in your wndprocs. This will allow them to be further processed by the default handler (as some msgs still require further processing by windows). ie WM_MOVING