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From: Gary.Pianosi@sunbrk.FidoNet.Org (Gary Pianosi)
Newsgroups: comp.windows.ms.programmer
Subject: Problem Reading Bitmaps from Clipboard
Message-ID: <675518012.5@sunbrk.FidoNet>
Date: 28 May 91 00:44:25 GMT
Sender: Usenet@sunbrk.FidoNet.Org
Lines: 55


I am trying to write a program that will read a bitmap from the
clipboard and save it out in another format.  However, the handle
returned from GetClipboardData() is sometimes invalid in the sense
that a GlobalLock() of that handle fails.  Also, the handle returned
is often not listed by Heap-Walker, or is labelled as being a handle
to an existing resource (menu, string, etc).

Following the example in the "Guide to Programming" (section 13.1.3),
I modified the CLIPTEXT sample to paste bitmaps instead of text from
the clipboard.  The pertinent code is as follows:

> case IDM_PASTE:
>   if (OpenClipboard(hWnd)) {
>       if (!(hClipData = GetClipboardData(CF_BITMAP))) {
>           CloseClipboard();
>           break;
>       }
>       if (!(lpClipData = GlobalLock(hClipData))) {
>           OutOfMemory();              /* <--- usually fails here */
>           CloseClipboard();
>           break;
>       }
>       /*
>        * ... do something with data at lpClipData ...
>        */
>       GlobalUnlock(hClipData);
>       CloseClipboard();
>   }

Sometimes the GlobalLock() works but usually it fails.  With a given
content in the clipboard it either always succeeds or always fails.

Miscellaneous info:
    - I'm using a 386 clone with 8 Meg of memory (also occurs using
        a PS/2 Model 80 with 2 Meg of memory).
    - I have tried both Microsoft C 6.00 and Borland Turbo C 2.0
    - occurs in 386-enhanced, Standard, and Real modes
    - occurs with both Windows 3.0 and Windows 3.00a

In an attempt to solve my problem by side-stepping it, I tried using
the GetBitmapBits() function to copy the bitmap data to a buffer.
It seems to work (even when the bitmap handle appears to be invalid!).
I guess I'm a little worried about leaving my problem unsolved since
the SDK suggests using GlobalLock() to look at the bitmap data.

Thanks in advance for any advice.

- Gary Pianosi.
-- 
--
E-mail:  garyp@csg.UWaterloo.CA                     Phone: (519) 888-4678
Computer Systems Group, University of Waterloo, Waterloo, Ontario, Canada

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