CDC::DrawState problem/bug?

Cliff Strass -- Cliff_Strass@mbnet.mb.ca
Friday, September 06, 1996

Environment: VC++ 4.0, NT 4.0 (beta2)

I have created my own custom control which, among other things, is supposed
to draw an icon or a bitmap. For the bitmap I use the CDC::BitBlt function,
and CDC::DrawIcon function for the icon. I want to be able to draw the
bitmap or icon in a disabled state, where the icon/bitmap appears to be
greyed out.
Using the CDC::DrawState with the nFlags parameter set to DSS_DISABLED
works, however it creates a first-chance exception, here is the exact
message I get:

	First-chance exception in myapp.exe (NTDLL.DLL): 0xC0000005: Access
Violation.

This causes the application to crash at other locations in the code. When I
remove the DrawState call, everything is working fine.

Has anyone been able to use this function without problems or is this a
bug. Note that this problem also occurs when I use the raw API function
::DrawState(...).

	CPoint picpt(x,y);
	CSize picsize(picWidth,picHeight);
	HBRUSH hBrush=NULL;
	// m_Bmp is a CBitmap with the coloured bitmap to draw in disabled mode
	BOOL check=pDC>DrawState(picpt, picsize, &m_hBmp, DSS_DISABLED, hBrush);

I would appreciate if anyone could help solve this function or if you know
of any other way of 'disabling' an icon or bitmap.

Regards, Cliff.

Cliff Strass
strass@mbnet.mb.ca
Winnipeg, Canada.

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Mike Blaszczak -- mikeblas@nwlink.com
Sunday, September 08, 1996

At 02:06 PM 9/6/96 -0500, you wrote:
>Environment: VC++ 4.0, NT 4.0 (beta2)

Windows NT 4.0 final has been shipping for three or four weeks.  Betas
are for testing purposes only--you should upgrade as soon as possible to
the released version of the operating system.

>Has anyone been able to use this function without problems or is this a
>bug. Note that this problem also occurs when I use the raw API function
>::DrawState(...).

I guess that means this isn't really an MFC question.  Since you're having
the problem with a beta operating system, and you've found that the
problem is not with MFC, maybe it would be far more appropriate for you to 
contact the beta suppotr folks identified in the beta kit.

>	CPoint picpt(x,y);
>	CSize picsize(picWidth,picHeight);
>	HBRUSH hBrush=NULL;
>	// m_Bmp is a CBitmap with the coloured bitmap to draw in disabled mode
>	BOOL check=pDC>DrawState(picpt, picsize, &m_hBmp, DSS_DISABLED, hBrush);

Why are you passing only DSS_DISABLED?  Shouldn't you be passing DST_ICON or
DST_PREFIX or'ed in there, as well?  Since DST_COMPLEX is defnied as 0, and
since you're not or'ing in any DST_* bits, the function thinks you mean
DST_COMPLEX.

Since you specify DST_COMPLEX, the function wants to call back the callback
you pass it via the lpOutputFunc you pass in.  Since you use this override in
MFC, the lpOutputFunc is passed by MFC as NULL.  Since you pass DSS_DISABLED
and a NULL lpOutputFunc, it seems like you're making an invalid call to the
function--and a first-chance exception in such a circumstance seems
understandable.

.B ekiM
http://www.nwlink.com/~mikeblas/
These words are my own. I do not speak on behalf of Microsoft.

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Roger Onslow/Newcastle/Computer Systems Australia/
Tuesday, September 10, 1996

>Using the CDC::DrawState with the nFlags parameter set to DSS_DISABLED

You should use DSS_DISABLED | DSS_ICON (or whatever)
You have to set both the image type and the state in the flag

> CPoint picpt(x,y);
> CSize picsize(picWidth,picHeight);
> HBRUSH hBrush=NULL;
> // m_Bmp is a CBitmap with the coloured bitmap to draw in disabled mode
> BOOL check=pDC>DrawState(picpt, picsize, &m_hBmp, DSS_DISABLED, hBrush);

Why "&m_hBmp" ??? I assume m_hBmp is a HBITMAP.
DrawState takes either "HBITMAP" or "CBitmap*", and "&m_hBmp" is neither of 
these, so MFC is having to do some conversion/casting here.
So try using just "m_hBmp" instead.

Roger Onslow

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