INFO: Transparent Windows

Microsoft Windows version does not support fully functional transparent windows.

If a window is created using CreateWindowEx() with the WS_EX_TRANSPARENT style, windows below it at the position where the original window was initially placed are not obscured and show through. Moving the WS_EX_TRANSPARENT window, however, results in the old window background moving to the new position, because Windows does not support fully functional transparent windows.

WS_EX_TRANSPARENT was designed to be used in very modal situations and the lifetime of a window with this style must be very short. A good use of this style is for drawing tracking points on the top of another window. For example, a dialog editor would use it to draw tracking points around the control that is being selected or moved.

In Windows 2000, specific colors in a window can be made truly transparent by giving the window the WS_EX_LAYERED extended style and calling SetLayeredWindowAttributes.