The Invisible Child Window
I'm currently busy making dockable tool windows for my program. I've conceived a "dock server" window that permits its "dock clients" (the tool windows) to become its children, along with another window which is the application workspace. I feel a tree coming on...
In my indeed infinite wisdom, I decreed that the dock server should be an "invisible" window, i.e. although it has a region that covers the client area of the frame window, it is transparent. With that in mind, I set its extended style to WS_EX_TRANSPARENT.
Application Frame Window
Dock Server-----------------------Undocked Tool Windows
Workspace Window Docked Tool Windows
This works fine until I actually dock a tool window and the workspace window is resized to give the docked window room. Because the frame window's style includes WS_CLIPCHILDREN, it doesn't erase the background underneath its children. This would normally be good (prevents flickering), but for a transparent window... :o
So, I tried using this in my dock server's WindowProc:-
This doesn't quite work, however. Any ideas?
HRGN hRgn, hrgnChild;
hRgn = CreateRectRgn(0, 0, 0, 0);
// Got update?
if (GetUpdateRgn(hWnd, hRgn, FALSE) != NULLREGION)
info = (t_dockserver *)GetWindowLong(hWnd, 0);
// Do we have a workspace?
// Clip it from the update region
MapWindowPoints(NULL, hWnd, (LPPOINT)&rc, 2);
hrgnChild = CreateRectRgnIndirect(&rc);
CombineRgn(hRgn, hRgn, hrgnChild, RGN_DIFF);
// Redraw this bit please
InvalidateRgn(GetParent(hWnd), hRgn, TRUE);