Owner Draw problems on NT

Mike Marshall -- marshall@milner.com
Tuesday, February 04, 1997

Environment: VC++ 4.2 flat, NT 4.0

I'm having problems with an owner draw list box in a dialog (actually in a
property sheet.)

On Wndows 95, everything works fine, but on NT 4.0, I get peculiar behavior.
I know I've seen discussions about something like on this list before, but looking 
back through my saved messages I can't seem to find anything referring to this
problem.

What happens is this.  I have an owner draw list box in a property page of a property
sheet.  I've overloaded DrawItem and MeasureItem and all that good stuff, and
implemented by custom drawing.

In some calls to DrawItem (not all, just some) I'm getting a strange decive context.
(the lpDrawItemStruct->hDC member).  So every time the function gets called,
I make a call to the win32 API function GetDeviceCaps(), passing it the hDC and
the TECHNOLOGY flag.  I expected to get DT_RASDISPLAY as the return value
every time, since I'm displaying to the screen (simple enough),  but to my surprise,
sometimes I get DT_PLOTTER back.  Now, I have no plotter devices attached
to my system, and this is totally throwing me for a loop. And like I said, this doesn't
happen under Win95.

The crux of my problem is that I'm trying to create a compatible DC, and you
cannot create a compatible DC from a DC that has DT_PLOTTER technology.

Has anyone seen this behavior before?  I know I've seen posts on this, but I've
scoured the newsgroups and MSDN and can't seem to find any references to it.

Help appreciated,
  Mike

---

Vijaya Kumar Eluri -- vijay@vedika.co.in
Friday, February 07, 1997

> From:          Mike Marshall 
> To:            "'MFC Listserv'" 
> Subject:       Owner Draw problems on NT

> Environment: VC++ 4.2 flat, NT 4.0
> 
> I'm having problems with an owner draw list box in a dialog (actually in a
> property sheet.)
> 
> On Wndows 95, everything works fine, but on NT 4.0, I get peculiar behavior.
> I know I've seen discussions about something like on this list before, but looking 
> back through my saved messages I can't seem to find anything referring to this
> problem.
> 
> What happens is this.  I have an owner draw list box in a property page of a property
> sheet.  I've overloaded DrawItem and MeasureItem and all that good stuff, and
> implemented by custom drawing.
> 
> In some calls to DrawItem (not all, just some) I'm getting a strange decive context.
> (the lpDrawItemStruct->hDC member).  So every time the function gets called,
> I make a call to the win32 API function GetDeviceCaps(), passing it the hDC and
> the TECHNOLOGY flag.  I expected to get DT_RASDISPLAY as the return value
> every time, since I'm displaying to the screen (simple enough),  but to my surprise,
> sometimes I get DT_PLOTTER back.  Now, I have no plotter devices attached
> to my system, and this is totally throwing me for a loop. And like I said, this doesn't
> happen under Win95.

I am also using something similar to what you are doing, but 
I don't have any problem on Wndows 95, and on NT 4.0. In both
environments I am getting DT_RASDISPLAY as expected till now.
I tested this using MSVC++ 4.2 and 4.1, but could not find
any problem.

-Vijay
 


__________________________________________________

Eluri Vijaya Kumar,
Vedika International Pvt Ltd,
21 Lansdowne Court,
5B Sarat Bose Road,
Calcutta - 700 020.
West Bengal, India.

Tel : +91-33-2473810.
Fax : +91-33-2479474.
email: vijay@vedika.co.in
__________________________________________________

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