The Face Object Field - Actors

From DocBase

Actors

The actors field of the compound object of a face is a map of the functions that define the behavior of the face. Whenever an event or other action occurs, these are the functions that handle it. (In some GUI systems, these are called interactors.)

If a style object is derived from a parent style, the parent actors are inherited from the parent object. But the derived actors are not bound to the parent. This allows the functions of the actor to be more efficiently reused in all instances of the face. Within an actor, a reference to a facet is made via special access functions.

Typical actors are:

on-make - when face is first created to initialize special values on-click - when mouse button clicked on face on-drag - when dragging inside a face on-drag-over - when dragging and are over a target face on-drop - when drag has stopped or when a file is dropped on-focus - when we have been given or are losing focus on-get - to fetch state values on-set - when state values are set on-clear - when the state values are cleared on-key - when key has been pressed (for our focus)

on-move - when mouse has moved on-over - when mouse passes over or away on-reset - when reset is needed on-resize - when size values have changed on-draw - when system starts to draw the face (create DRAW block) on-scroll - when scrolling is needed on-scroll-event - when the mouse wheel is used on-init - when face and its parent pane are ready (including initial sizing) on-attach - when a face is attached to another face

There is no need to define actors that are not needed. New actors can be created as required.

Actor functions are called using the DO-STYLE function. For example:

 do-style face 'on-click true

The action is ignored if the face has no on-click actor.