Let's say you want to add a little extra graphical info to a Windows control. For example, you want to add drag/drop functionality to a listview (using the procedure discussed here), but with horizontal lines signaling the drop/insertion points as the user drags an item. (The control belongs to your own application.)
Is there a safe way to subclass the control and draw onto it directly? In my limited experimentation in trying to do this, I encountered some problems. First, it wasn't clear whether I should call BeginPaint
and EndPaint
during the WM_PAINT
message, since the control itself would be calling those functions once the message was passed along to the default procedure. I also inevitably encountered flickering, since some areas were being painted twice.
I thought a safer way would be just to create a transparent overlay window and draw on that, since that would avoid conflicts with the default paint procedure, but I thought I'd ask before going down that road. Thanks for any advice.
question from:
https://stackoverflow.com/questions/65855025/is-there-a-safe-way-to-paint-a-little-extra-onto-a-subclassed-control 与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…