Blitting compatable dc to compatable dc does not work.

[aewarnick]

//creation of the 2 dc's. hdc is screen.
HDC memDC= ::CreateCompatibleDC(hdc);
HDC imageDC= ::CreateCompatibleDC(hdc);

//created drawing surface fo the memDC
HBITMAP hMemBmp= ::CreateCompatibleBitmap(hdc, wndRect.right-wndRect.left,
wndRect.bottom-wndRect.top);

//Selecting bmp's into dc's
HBITMAP hOldBmp= (HBITMAP)::SelectObject(imageDC, hBmp->HBmp);
HBITMAP hOldMemBmp= (HBITMAP)::SelectObject(memDC, hMemBmp);

//drawing background on memDC
::StretchBlt(memDC, 0, 0, wndRect.right-wndRect.left,
wndRect.bottom-wndRect.top, imageDC, 0, 0, BmpW, BmpH, SRCCOPY);

//Attempt to copy the memDC to another dc yeilds a black box
//and not the image!
::BitBlt(imageDC, drawLocation->left, drawLocation->top, BmpW, BmpH, memDC, drawLocation->left, drawLocation->top, SRCCOPY);

[aewarnick]

My mistake. I could not see it! It's exactly the same as the background! Bad mistake!

[kedaman]

the old bitmaps seems a bit redundant there, you've just created them dcs

[aewarnick]

I have no idea what you are talking about but do you know how to create another object in memory just like a chosen object? Like a Bitmap?
Do I use
::CreateCompatibleBitmap for a Bitmap?
What about anything else?

[kedaman]

yes, you can read more on msdn for creating other GDI objects http://msdn.microsoft.com/library/en...asp?frame=true
I just pointed out that these:
HBITMAP hOldBmp=
HBITMAP hOldMemBmp=
were redundant, as there are no bitmaps for the new dcs

[aewarnick]

But don't I have to Select them out of the dc's and then delete the HBitmap's when I'm done?

[kedaman]

of course you have to.

[aewarnick]

Thanks. Are you trying to confuse me?

[kedaman]

no, i certainly didn't intend to and i hope i didn't.

[aewarnick]

Are you saying that these
HBITMAP hOldBmp=
HBITMAP hOldMemBmp=
are NULL?

[kedaman]

well now i'm not sure in fact, most of the time i see people even on msdn not deleting the objects.. so now that you mentioned it (and i used to take it for granted) it does return a 1x1 bitmap - and doing it again returns the same bitmap.. sorry if it seems confusing, but it seems to me as you should not delete it after all. Yet you should delete all bitmaps you create on your own.

[aewarnick]

Thank you very much. My code is now improved and probably a little faster.

[aewarnick]

I read this article: CLICK
and as you see, it mentions that there is a default Bitmap in the DC's that MS was not Selecting the Old hbitmaps back into the dc's and there was a leak.

[kedaman]

thanks.. seems like microsoft can't keep track on anything but thats nothing new then..