GlobalSize function used on Clipboard Data cause error - c++

Question

The first thing I want to say is my English is pretty bad so if my description become a chunk of nonsense text please comment so I can try to clarify my question.
The situation
I'm trying to access clipboard and store all of it's data from all formats possible. I listen to WM_CLIPBOARDUPDATE message then loop through all the format available, get the data for each of the format, get the size then allocate a new memory for them. My googling tell me to use the GlobalSize() function to do that. There the problem arise.
The environment
I am developing a Win32 desktop application using C++ on Visual C++ 2017 version 4.7.02556. I am using Windows 10 64 bits if that matter.
Reproducing the error
Here is my function used to process Windows messages, I remove other message like WM_CREATE or WM_DESTROY because they don't relate to the problem. The consoleOutput() function is used for debugging and they works just fine.
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam){
switch (message){
case WM_CLIPBOARDUPDATE: {
try {
if (OpenClipboard(hWnd)){
UINT uFormat = EnumClipboardFormats(0); // Get the first clipboard format available
HANDLE hContent;
while (uFormat) { //Iterate through all formats
hContent = GetClipboardData(uFormat); // Get the clipboard data of that format
if (hContent) {
SIZE_T size = GlobalSize(hContent); // Get the size of the data I just got
//ERROR
}
uFormat = EnumClipboardFormats(uFormat); // Get the next format
}
}
CloseClipboard();
}
catch (int error) {
CloseClipboard(); // Attempt to close clipboard if thing went wrong
consoleOutput(GetLastError());
throw;
}
}
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
The code works fine with everything I tried to copy from text to some random files/directories. But my program gave me an error when I tried to copy a image, for example:
Open an image using MS Paint, select any portion of the image and copy it and the error appears.
Open an image using Picasa, right click and select copy and the error appears.
Press PrntScr button and the error appears.
The error is throwed at SIZE_T size = GlobalSize(hContent); line, and it is either:
Critical error detected c0000374 YClipboard.exe has triggered a breakpoint.
or
Exception thrown at 0x77E17ECC (ntdll.dll) in YClipboard.exe: 0xC0000005: Access violation reading location 0xDD46116F.
The error is not persistent, most of the time it appeared right in the first copy, sometime I can copy the image, but do it multiple times with that same image cause the error. Above all, only attempt to copy "image" data cause the problem.
What I have tried so far
I am a novice about developing desktop app, and I my searching don't find the problem anywhere else. When I peek at the clipboard data using a third-party app, I found out the error only appear when my program met the CF_BITMAP or CF_METAFILEPICT format, and (not so) coincidentally both of those formats have a memory of size 0. Still I am unable to fix my problem.
What I need
Someone please enlighten me about this problem: what is the problem, the cause of it, how to fix it or just a suggestion about another method that help me read the size of clipboard data to replace GlobalSize() function.
Thanks in advance.

Answer 1

Not all clipboard formats present an HGLOBAL that you can use with functions like GlobalSize().
For example, CF_BITMAP presents a handle to a bitmap; an HBITMAP that you can use with functions like GetObject().
You'll need to handle those formats specially. See the Standard Clipboard Formats list on MSDN for more information.