Swing Hacks

Add a Third Dimension to Swing #63

Chapter 8, Rendering

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319

HACK

As you can see, you end up with a black background in the Canva3D. Because

the only way to get rid of a component’s background is to call

setOpaque(false)

—which is defined by

JComponent

and thus isn’t available

to AWT components—you are stuck with this ugly background. Indeed, as

a lightweight component, the canvas cannot be made transparent. Things

get even worse when you try to add a menu bar to the application because of

the order in which components are painted: lightweight first, heavyweight

next. Figure 8-10 shows an example of what happens when a pop-up menu

is drawn by Swing. Because it is a lightweight component, it is drawn before

Canvas3D

, when it should be drawn after the canvas.

Thankfully, this new problem (it’s all AWT’s fault!) was so annoying that

the Swing team decided to add a workaround for it. You can simply force all

pop-up menus of your applications to be created as heavyweight compo-

nents instead of lightweight components. A single line of code is enough to

fix the problem:

JPopupMenu.setDefaultLightWeightPopupEnabled(false);

If you invoke this method before you create the first JMenu or JPopupMenu,

you ensure your menus will be drawn on top of heavyweight components.

So, this takes care of one issue, but you still need to deal with the black

background problem.

Faking Transparency

Because you cannot change the