Question

How do I copy a buffer that would save to a ".BMP" file to the clipboard using the win32 API? I.e., I have a raw buffer of a Windows V3 Bitmap (including the header) that I can literally write() to a file and will result in a valid .BMP file, but I want to copy it to the clipboard instead.

On OS X, in plain C, the code would look something like this (which works as intended):

#include <ApplicationServices/ApplicationServices.h>
int copyBitmapToClipboard(char *bitmapBuffer, size_t buflen)
{
 PasteboardRef clipboard;
 CFDataRef data;

 if (PasteboardCreate(kPasteboardClipboard, &clipboard) != noErr) {
  return PASTE_OPEN_ERROR;
 }

 if (PasteboardClear(clipboard) != noErr) return PASTE_CLEAR_ERROR;

 data = CFDataCreateWithBytesNoCopy(kCFAllocatorDefault, bitmapBuffer, buflen,
                                    kCFAllocatorNull);
 if (data == NULL) {
  CFRelease(clipboard);
  return PASTE_DATA_ERROR;
 }

 if (PasteboardPutItemFlavor(clipboard, 42, kUTTypeBMP, data, 0) != noErr) {
  CFRelease(data);
  CFRelease(clipboard);
  return PASTE_PASTE_ERROR;
 }

 CFRelease(data);
 CFRelease(clipboard);
 return PASTE_WE_DID_IT_YAY;
}

I am unsure how to accomplish this with the win32 API. This is as far as I’ve gotten, but it seems to silently fail (that is, the function returns with a successful error code, but when attempting to paste, the menu item is disabled).

#include <windows/windows.h>
int copyBitmapToClipboard(char *bitmapBuffer, size_t buflen)
{
 if (!OpenClipboard(NULL)) return PASTE_OPEN_ERROR;
 if (!EmptyClipboard()) return PASTE_CLEAR_ERROR;

 if (SetClipboardData(CF_DSPBITMAP, bitmapBuffer) == NULL) {
  CloseClipboard();
  return PASTE_PASTE_ERROR;
 }

 CloseClipboard();
 return PASTE_WE_DID_IT_YAY;
}

Could anyone provide some insight as to how to fix this?

Edit

Per Aaron and martinr’s suggestions, I’ve now modified the code to the following:

#include <windows/windows.h>
int copyBitmapToClipboard(char *bitmapBuffer, size_t buflen)
{
 HGLOBAL hResult;
 if (!OpenClipboard(NULL)) return PASTE_OPEN_ERROR;
 if (!EmptyClipboard()) return PASTE_CLEAR_ERROR;

 hResult = GlobalAlloc(GMEM_MOVEABLE, buflen);
 if (hResult == NULL) return PASTE_DATA_ERROR;

 memcpy(GlobalLock(hResult), bitmapBuffer, buflen);
 GlobalUnlock(hResult);

 if (SetClipboardData(CF_DSPBITMAP, hResult) == NULL) {
  CloseClipboard();
  return PASTE_PASTE_ERROR;
 }

 CloseClipboard();
 return PASTE_WE_DID_IT_YAY;
}

But it still has the same result. What am I doing wrong?

Final Edit

The working code:

#include <windows/windows.h>
int copyBitmapToClipboard(char *bitmapBuffer, size_t buflen)
{
 HGLOBAL hResult;
 if (!OpenClipboard(NULL)) return PASTE_OPEN_ERROR;
 if (!EmptyClipboard()) return PASTE_CLEAR_ERROR;

 buflen -= sizeof(BITMAPFILEHEADER);
 hResult = GlobalAlloc(GMEM_MOVEABLE, buflen);
 if (hResult == NULL) return PASTE_DATA_ERROR;

 memcpy(GlobalLock(hResult), bitmapBuffer + sizeof(BITMAPFILEHEADER), buflen);
 GlobalUnlock(hResult);

 if (SetClipboardData(CF_DIB, hResult) == NULL) {
  CloseClipboard();
  return PASTE_PASTE_ERROR;
 }

 CloseClipboard();
 GlobalFree(hResult);
 return PASTE_WE_DID_IT_YAY;
}

Thanks, martinr!

Answer 1

I think the hMem needs to be a return value from LocalAlloc, an HMEMORY rather than a pointer.

EDIT

Sorry yes, GlobalAlloc with GMEM_MOVEABLE is required, not LocalAlloc.

EDIT

I suggest you use CF_DIB clipboard data format type.

DIB is the same as BMP except it is without the BITMAPFILEHEADER, so copy the source bytes except for the first sizeof(BITMAPFILEHEADER) bytes.

EDIT

From OpenClipboard() documentation (http://msdn.microsoft.com/en-us/library/ms649048(VS.85).aspx):

“If an application calls OpenClipboard with hwnd set to NULL, EmptyClipboard sets the clipboard owner to NULL; this causes SetClipboardData to fail.”

You need to set up a window; even if you’re not doing WM_RENDERFORMAT type stuff.

I found this a lot with Windows APIs. I haven’t used the Clipboard APIs per se but with other APIs I usually found that creating a hidden window and passing that handle to the relevant API was enough to keep it quiet. There’s usually some notes on issues to do with this if you’re creating a window from a DLL rather than an EXE; read whatever is the latest Microsoft word about DLLs, message loops and window creation.

As regardsBITMAPINFO, that’s not the start of the stream the clipboard wants to see :- the buffer you give to SetClipboardData should start right after where the BITMAPFILEHEADER stops.