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Dec 2nd, 2007

Pointer to a structure

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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

C++ Syntax (Toggle Plain Text)

MINMAXINFO *Info;
Info = MINMAXINFO *wParam;

and several other variations to no avail.

Thanks

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Tight_Coder_Ex

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Posting Whiz in Training

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Dec 2nd, 2007

Re: Pointer to a structure

Just cast it the usual way:

C++ Syntax (Toggle Plain Text)
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.

Duoas

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Postaholic

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Dec 3rd, 2007

Re: Pointer to a structure

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

C++ Syntax (Toggle Plain Text)
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;

Tight_Coder_Ex

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Dec 3rd, 2007

Re: Pointer to a structure

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.

Duoas

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Postaholic

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Dec 3rd, 2007

Re: Pointer to a structure

I also remebered the way I wanted to do it

C++ Syntax (Toggle Plain Text)

        LPMINMAXINFO  Info
        Info = LPMINMAXINFO (lParam)

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

Tight_Coder_Ex

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Dec 3rd, 2007

Re: Pointer to a structure

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.

Duoas

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