Disposable resources

Operating system user interfaces don't have garbage collectors to automatically dispose of resources. SWT respects this.

The method you need for this is called dispose. The rule is, "If you created it, you dispose it, unless you set it on a widget and the widget now owns it."

Common things that need to be disposed

This means that, if you create a graphics resource, you have to dispose of it to avoid leaking these resources. What are common examples?

• Color objects
• Fonts
• Graphics contexts for drawing on a canvas (or a Drawable).

You can avoid a lot of this headache by using fonts, colors, etc., that are already defined by the operating system. See getSystemColor on the Display class, for example.

Consult the SWT documentation for more.

Drawing on a graphics context

Regarding this latter case, Clojure Desktop Toolkit supplies a macro to help. doto-gc-on works like Clojure's doto, but crates a graphics context, executes your drawing commands on that graphics context, and then automatically disposes it for you. Here's an example:

(doto-gc-on image
            (. setBackground (.getSystemColor display SWT/COLOR_DARK_BLUE))
            (. fillRectangle (.getBounds image)))

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