🚀 go-pugleaf

esuvx@csv.warwick.ac.uk (Adge) wrote:

>I am programming in ms Visual C++ v.4.0 under Win95, and am trying to 
>persuade it to allow me to draw graphics to a window from a procedure other
>than OnPaint or OnDraw.
>
>I have tried using CPaintDC(this); , but this gives an access violation.


         First, you must tell us this; is your program multithreaded, and 
are you trying to draw in a thread other than the one that is allowed use 
MFC? I don't have the answer for you, but I know we need that information.


                        David

In article <4iuni1$oep@lily.csv.warwick.ac.uk> esuvx@csv.warwick.ac.uk (Adge) writes:
>
>I am programming in ms Visual C++ v.4.0 under Win95, and am trying to 
>persuade it to allow me to draw graphics to a window from a procedure other
>than OnPaint or OnDraw.
>
>I have tried using CPaintDC(this); , but this gives an access violation.
>
>It used to be possible under Borland Pascal for win but I can't work out
>how to do it under visc++
>
>Can anyone help ?
	If you respond to WM_PAINT, then you are provided with an HDC
	(presumably your OnPaint does the BeginPaint/EndPaint stuff for you).

	If you wish to draw at any other time, you need to obtain an HDC,
	i.e. with GetDC(). Do your drawing and then ReleaseDC().

	However, there is a very good reason for doing *ALL* of your drawing
	at WM_PAINT. Consider what happens if you draw something anytime you
	want (i.e. not at WM_PAINT).  Your picture looks fine, right?  Ok,
	now what happens if your app is covered/uncovered by a dialog box
	or another app? That generates WM_PAINT and you will draw part of
	the picture, but not the part that you drew separately.  Remember
	that you must be prepared to paint any or all of your picture at
	any time at WM_PAINT.
-- 
John A. Grant						jagrant@emr1.emr.ca
Airborne Geophysics
Geological Survey of Canada, Ottawa