Volume 7A: XView Programming Manual

6

Handling Input

In discussing canvases in the previous chapter, we showed how to do some basic event hand-

ling in the canvas’s paint window. This chapter goes into detail about the content of such

events, the breakdown of the Event data structure that describes the event, the different

types of input events that can be handled, and the specifics about what gets passed to the pro-

gram’s event handling callback routine. Chapter 20, The Notifier, should be reviewed for an

in-depth discussion of how to handle events on a somewhat more advanced level. It

addresses the event types themselves, how to register which events you want to be notified

of, and how to interpret the events you receive.

This chapter also describes the interface to the special keyboard and mouse features includ-

ing soft function keys, virtual keyboards, mouseless model keyboard mappings, and accelera-

tor keys. These features support OPEN LOOK Level 2 functions that permit you to use multi-

ple “virtual keyboards,” and software-supported function keys. You also have the option of

using the keyboard as a locator device along with or in place of a mouse.

This chapter discusses the following:

• The design of event handling.

• The breakdown of the Event data structure.

• Registering an event handler and the events you are interested in.

• Interpreting the events your event handler received.

• Sending messages to other windows or clients. ...