WIN32 IsClipboardFormatAvailable function does not set last error code

Question

In documentation

If the clipboard format is not available, the return value is zero. To get extended error information, call GetLastError. IsClipboardFormatAvailable function (winuser.h)

but the output of this code is 0:

#include <Windows.h>
#include <cstdio>
#include <winerror.h>
int main()
{
    //I copied an image to the clipboard before running the program
    if(!IsClipboardFormatAvailable(CF_UNICODETEXT))
    {

        printf("%lu", GetLastError());
    }
}

Why didn't the IsClipboardFormatAvailable function set the last error?

Answer 1

I've seen this pattern before. Typically IsClipboardFormatAvailable() is not a function that can fail; and there's not expected to be anything useful to report because the last thing in the clipboard just doesn't match any known format.

If you're really in a situation where IsClipboardFormatAvailable() can fail and need to check and do something about the difference, this fragment is correct:

   SetLastError(0);
   if(!IsClipboardFormatAvailable(CF_UNICODETEXT))
   {
       if (GetLastError() == 0)
       {
           printf("Clipboard doesn't contain text.");
       } else {
           printf("IsClipboardFormatAvailable: %lu", GetLastError());
       }
   }

You described a case of image in the clipboard in the question. The function didn't fail.