DaniWeb Forum Index > Software Development > C++

Pointer to a structure

Please support our C++ advertiser: Intel Parallel Studio Home

Thread Solved

•

Join Date: Feb 2005

Posts: 199

Reputation: Tight_Coder_Ex is an unknown quantity at this point

Solved Threads: 14

Tight_Coder_Ex Tight_Coder_Ex is offline

Offline

Junior Poster

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

Help with Code Tags

C++ Syntax (Toggle Plain Text)

MINMAXINFO *Info;
Info = MINMAXINFO *wParam;

and several other variations to no avail.

Thanks

•

Join Date: Oct 2007

Posts: 1,953

Reputation: Duoas has much to be proud of

Solved Threads: 214

Duoas

Offline

Posting Virtuoso

Re: Pointer to a structure

Dec 2nd, 2007

Just cast it the usual way:

 Help with Code Tags 
 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.

•

Join Date: Feb 2005

Posts: 199

Reputation: Tight_Coder_Ex is an unknown quantity at this point

Solved Threads: 14

Tight_Coder_Ex Tight_Coder_Ex is offline

Offline

Junior Poster

Re: Pointer to a structure

Dec 3rd, 2007

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

 Help with Code Tags 
 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;

•

Join Date: Oct 2007

Posts: 1,953

Reputation: Duoas has much to be proud of

Solved Threads: 214

Duoas

Offline

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.

•

Join Date: Feb 2005

Posts: 199

Reputation: Tight_Coder_Ex is an unknown quantity at this point

Solved Threads: 14

Tight_Coder_Ex Tight_Coder_Ex is offline

Offline

Junior Poster

Re: Pointer to a structure

Dec 3rd, 2007

I also remebered the way I wanted to do it

Help with Code Tags

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?

•

Join Date: Oct 2007

Posts: 1,953

Reputation: Duoas has much to be proud of

Solved Threads: 214

Duoas

Offline

Posting Virtuoso

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.