If you use $dll() it is loaded into the same process, so it should work. Tested here using a DLL and $dll() and it captured the @window into a bitmap, whether visible or hidden, although when hidden, the titlebar and frame are missing, which are beyond mIRC's ability to control. Are you sure you are using the correct window handle? Have you tried copying the resulting bitmap to the clipboard instead?
OpenClipboard(hWnd);
EmptyClipboard();
SetClipboardData(CF_BITMAP, hbm);
CloseClipboard();
I am using the same code as suggested earlier in this thread. Unfortunately I really cannot dedicate any more time to this - I have spent many hours on it already. I would suggest that you create a separate application that itself handles WM_PAINT/WM_PRINT/WM_PRINTCLIENT to see if you can get it to work.
