A path toward fluency

Congratulations! You now know:

• The conventions Clojure Desktop Toolkit uses to map between its own API and SWT's API.
• Basic SWT API conventions you can use to quickly understand and apply SWT's API.

How does one move from this place to becoming proficient with SWT and Clojure Desktop Toolkit?

SWT is a fairly large API. While its consistent use of conventions helps, each widget has its own nuances.

Further, being a native widget toolkit introduces its own complexities.

Here are some tactics and approaches that will help you manage this complexity as you learn.

Event handling using native widgets

Since SWT wraps native platform widgets, the order in which you receive what events will not be consistent across platforms! Here is a best practice to help manage this:

Never mutate user interface state from within an event handler itself

• If you do this, you will interrupt pending event chains in ways that are unpredictable, particularly across platforms. This results in undefined behavior.
• Instead, use the async-exec! function within your event handler to queue a function that will execute your state changes after all pending events have completed!

For example, if the user clicks the mouse on a text field to move the focus there, the user interface will generate a sequence of events something like:

• mouse-down
• traverse event (can we leave the old control?)
• focus-out (from the old control)
• focus-in (to the new control)
• mouse-up

Unless you're going to use event's doit flag to block the traverse event from continuing, you will want to place any additional state changes after the mouse-up event. The way to do this is via the async-exec! function from mouse-down or traverse event so that your code runs after the final mouse-up.

The docstrings for the ui macro along with sync-exec! and async-exec! offer more color.

SWT's example encyclopedia

There's an encyclopedia of SWT code examples, organized by SWT widget! It's called the "SWT snippet" library over at Eclipse.org and it's amazing!

Using these examples, you can learn how to accomplish pretty much any esoteric thing using SWT!

More SWT hints

The following section in the tutorial index introduces more of SWT's API and offers a quick reference guide to the current SWT API.

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