Unfortunately, using this method, the X server permits very few operations to be performed on the background pixmap (such as XOR), preventing clients from implementing any sort of advanced image filtering.
Using this information, a client can paint a section of the image (corresponding to the size and position of the window) onto its background, achieving the effect of transparency.
This method uses the most memory, but has the advantage of allowing clients to perform any operation, such as tinting or shading, on the image data.
This method simply uses the XCopyArea() function to take a partial screenshot for use as the window's background pixmap.
Recent technologies such as DirectFB, Direct Rendering Infrastructure, and hardware compositing via OpenGL allow X client applications to utilize true alpha transparency.