GUI- Events and Actors

Events:

Mouse clicking, mouse hovering, key pressing etc., are events that you may want to associate with code. We saw on last chapter that there is something called action facet that executes code triggered by a default event. You can add more blocks of code associated with events by following this layout:

There is an extensive list of possible events in the documentation. I copied it at the end of this chapter for reference.

Each face accepts a set of events, i.e. not all events apply to all faces.

I made a short set of examples. I see no point in giving examples of each existing event, since the logic is the same:

down - left mouse button pressed; over - mouse cursor passing over a face;

wheel - mouse wheel being turned;

key-down - a key has been pressed;

time - the delay set by face’sratefacet expired.

The following example "blinks" a text at a 1 second rate (see rate in chapter GUI- Advanced topics):

close - this is a window event: the window was closed. Very useful to include code to be executed when the user quits (closes the window).

Actors

Actors is the name of the event handling functions in Red. That is: the code inside brackets after on-<event> . So why not call them just event handlers like every other language does? I think is because they are an object inside the face as you can see if you run this code below and click on the area face:

Red [Needs: 'View]
view [
    t: area 40x40 blue
    on-down [print t] ;click to quit
    on-over [either t/color = red [t/color: blue][t/color: red]]
]

You will see in the console, nearly at the end of the print, an object with the actors described:

Full list of event names:

Notes:

• touch events are not available for Windows XP.+

• One or moremovingevents always precedes amoveone.

• One or moreresizingevents always precedes aresizeone.