I'm having problems using the DWM functionality of Windows Vista/7 on Java windows. I want to make the background of my frame use the Aero style. The Windows API to do so is provide by the function DwmExtendFrameIntoClientArea in the dwmapi library. I've managed to call the procedure properly via JNA, and it does what it is supposed to do (You can see that for example when resizing the frame, before the next repaint you see the proper aero effects in the area not yet painted, see the attached image).

But somewhere (I can't figure out where) a background is painted over the Aero effect and the effect is lost.

What I have already tried:

• Using a custom ContentPane with opacity set to false
• Setting the opacity of the LayeredPane and the RootPane to false
• Using a Frame instead of a JFrame
• Set the background color of the JFrame/ContentPane to black/fully transparent
• Use setLayersOpaque and a custom variant thereof, see first answer for more details

So far I could not succeed removing that background. Is it a limitation of AWT/Swing? How can I remove that background or use the Aero effect properly?

Your help is greatly appreciated.

Screenshot

Here a screenshot of a frame without any contents, having set the opacity of the RootPane, LayeredPane and ContentPane to false. I did it quickly while resizing. You see that the effect is properly applied to the area Java did not yet paint on.

http://i55.tinypic.com/v614qo.png (As a new user I cannot post the image directly...)

Odd behavior

Upon further investigation I came across the following odd behavior. If the window size is 150x150 or below the contents are displayed transparently. This is