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Pointer to a structure

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Join Date: Feb 2005

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Tight_Coder_Ex Tight_Coder_Ex is offline

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Pointer to a structure

Dec 2nd, 2007

How would I declare a pointer to MINMAXINFO that is passed to WPARAM

In WM_GETMINMAXINFO wParam is a pointer to a place on the stack that holds MINMAXINFO. I've tried

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MINMAXINFO *Info;
Info = MINMAXINFO *wParam;

and several other variations to no avail.

Thanks

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Duoas

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Posting Virtuoso

Re: Pointer to a structure

Dec 2nd, 2007

Just cast it the usual way:

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LRESULT CALLBACK MyWndProc(
  HWND   hWnd,
  UINT   uMsg,
  WPARAM wParam,
  LPARAM lParam
  ) {
  if (uMsg == WM_GETMINMAXINFO) {
    cout << "Max Window Size is ("
         << ((LPMINMAXINFO)lParam)->x << ", "
         << ((LPMINMAXINFO)lParam)->y << ")"
         << endl;
    }
  return DefWindowProc( hWnd, uMsg, wParam, lParam );
  }
LRESULT CALLBACK MyWndProc(
  HWND   hWnd,
  UINT   uMsg,
  WPARAM wParam,
  LPARAM lParam
  ) {
  if (uMsg == WM_GETMINMAXINFO) {
    cout << "Max Window Size is ("
         << ((LPMINMAXINFO)lParam)->x << ", "
         << ((LPMINMAXINFO)lParam)->y << ")"
         << endl;
    }
  return DefWindowProc( hWnd, uMsg, wParam, lParam );
  }

Hope this helps.

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Re: Pointer to a structure

Dec 3rd, 2007

Thank-you Duoas, my adaptation is as follows and works as expected

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case	WM_GETMINMAXINFO:
	((LPMINMAXINFO) lParam)->ptMinTrackSize.x = WndInfo.MaxWidth;
	((LPMINMAXINFO) lParam)->ptMaxTrackSize.x = WndInfo.MaxWidth;
	((LPMINMAXINFO) lParam)->ptMaxTrackSize.y = WndInfo.MaxHeight;
	((LPMINMAXINFO) lParam)->ptMinTrackSize.y = WndInfo.MinHeight;
   break;
case	WM_GETMINMAXINFO:
	((LPMINMAXINFO) lParam)->ptMinTrackSize.x = WndInfo.MaxWidth;
	((LPMINMAXINFO) lParam)->ptMaxTrackSize.x = WndInfo.MaxWidth;
	((LPMINMAXINFO) lParam)->ptMaxTrackSize.y = WndInfo.MaxHeight;
	((LPMINMAXINFO) lParam)->ptMinTrackSize.y = WndInfo.MinHeight;
   break;

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Join Date: Oct 2007

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Posting Virtuoso

Re: Pointer to a structure

Dec 3rd, 2007

Heh, nice job. Sorry I goofed in my example and left the ptMaxSize part out:
((LPMINMAXINFO)lParam)->ptMaxSize.x

Good job on picking that up! Glad you got it working.

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Re: Pointer to a structure

Dec 3rd, 2007

I also remebered the way I wanted to do it

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        LPMINMAXINFO  Info
        Info = LPMINMAXINFO (lParam)

I don't believe their is any advantage this way other than less to type and easier to read?

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Join Date: Oct 2007

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Duoas

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Re: Pointer to a structure

Dec 3rd, 2007

If your window procedure is small, then that way is an advantage because it is, in fact, less typing.

If your window procedure is very long then it is a disadvantage only because it separates what "info" is from where it is used.

But you are correct, they are otherwise identical.