how does Windows implement clipboard format conversion?

Question

i am implementing clipboard for my application sandbox system on Windows. I have to simulate clipboard behaviors by myself. Now all work fine except for format conversion part, i can do it for CF_TEXT/UNICODETEXT/OEMTEXT, but there are other formats that i am not familiar with like DIB. Is there any sample codes illustrating how Windows does this?

Answer 1

The difference between CF_DIB and other clipboard formats is that it contains memory objects of BITMAPINFO structure and bitmap bits.

The msdn document has provided a very detailed example:

HINSTANCE hinst; 
UINT uFormat = (UINT)(-1); 
BOOL fAuto = TRUE; 
 
LRESULT APIENTRY MainWndProc(hwnd, uMsg, wParam, lParam) 
HWND hwnd; 
UINT uMsg; 
WPARAM wParam; 
LPARAM lParam; 
{ 
    static HWND hwndNextViewer; 
 
    HDC hdc; 
    HDC hdcMem; 
    PAINTSTRUCT ps; 
    LPPAINTSTRUCT lpps; 
    RECT rc; 
    LPRECT lprc; 
    HGLOBAL hglb; 
    LPSTR lpstr; 
    HBITMAP hbm; 
    HENHMETAFILE hemf; 
    HWND hwndOwner; 
 
    switch (uMsg) 
    { 
        case WM_PAINT: 
            hdc = BeginPaint(hwnd, &ps); 
 
            // Branch depending on the clipboard format. 
 
            switch (uFormat) 
            { 
                case CF_OWNERDISPLAY: 
                    ...
 
                case CF_BITMAP: 
                    hdcMem = CreateCompatibleDC(hdc); 
                    if (hdcMem != NULL) 
                    { 
                        if (OpenClipboard(hwnd)) 
                        { 
                            hbm = (HBITMAP) 
                                GetClipboardData(uFormat); 
                            SelectObject(hdcMem, hbm); 
                            GetClientRect(hwnd, &rc); 
 
                            BitBlt(hdc, 0, 0, rc.right, rc.bottom, 
                                hdcMem, 0, 0, SRCCOPY); 
                            CloseClipboard(); 
                        } 
                        DeleteDC(hdcMem); 
                    } 
                    break; 
...

If you need to save the obtained bitmap object as a file, then you must strictly follow the BITMAPINFOHEADER structure to assign values.

MSDN code sample: Storing an Image