Question About Line Drawing with Messaging

Hi, I'm new to windows programming, and I'm trying to make it draw lines to wherever the user clicks. Right now I have this, and it works, but I think there must be a better way to send the message to WM_PAINT than passing -1 as the wParam.

-----------

switch (message)
{
case WM_PAINT:
BeginPaint(hWnd, &ps);
hdc = GetDC(hWnd);
if(wParam == -1)
LineTo(hdc, LOWORD(lParam), HIWORD(lParam));
EndPaint(hWnd, &ps);
break;

case WM_LBUTTONDOWN:
PostMessage(hWnd,WM_PAINT,-1,lParam);
break;

case WM_DESTROY:
PostQuitMessage(0);
break;

default:
return DefWindowProc(hWnd, message, wParam, lParam);
}

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Thanks!

first watch the GetXX() and CreateXX() functions as they allocate GDI memory.

All GetXX() must have a ReleaseXX()
All CreateXX() must have a DeleteXX()

Use

Code:

---

hdc=BeginPaint(hwnd,&ps);//or use the one in the ps struct
if(wParam == -1)
  LineTo(hdc, LOWORD(lParam), HIWORD(lParam));
EndPaint(hwnd,&ps);

---

Does this have a problem drawing the line in the right spot if the window is not full screen?
Does the line stay there always?

Where is the call to to set the pen pos before LineTo() (especially on the first drawing of the line)
MoveToEx(hdc,XCood,YCood,(LPPOINT)NULL);


To send a paint msg you can use
InvalidateRect() or UpdateWindow() or RedrawWindow()

You should create a compatible DC, bitmap ect and draw to it. Then BitBlt() this HDC to your 'hdc' in response to a WM_PAINT.
Use GetUpdateRect() before your WM_PAINT to find the area that needs redrawing.

(try a search here as there is lots of code on paint functions posted)

Ok thanks. But that doesn't mean I need DeleteWindowEx() because of my CreateWindowEx() does it?

No, The DestroyWindow() should cover that.

Only for the GDI functions inc Create* / Get

(Font, brush, pen, bitmap and DC.)