MATLAB Creating Graphical User Interfaces

13 Manage Callback Execution

Interrupt Callback Execution

In this section...

“How to Control Interruption” on page 13- 2

“Callback Behavior When Interruption is Allowed” on page 13- 2

“Example” on page 13- 3

MATLAB lets you control whether or not a callback function can be interrupted while

it is executing. For instance, you can allow users to stop an animation loop by creating

a callback that interrupts the animation. At other times, you might want to prevent

potential interruptions, when the order of the running callback is important. For

instance, you might prevent interruptions for a WindowButtonMotionFcn callback that

shows different sections of an image.

How to Control Interruption

Callback functions execute according to their order in a queue. If a callback is executing

and a user action triggers a second callback, the second callback attempts to interrupt

the first callback. The first callback is the running callback. The second callback is the

interrupting callback.

Two property values control the response to an interruption attempt:

• The Interruptible property of the object owning the running callback determines if
  interruption is allowed. A value of 'on' allows the interruption. A value of 'off'
  does not allow the interruption. The default value is 'on'.


• If interruption is not allowed, then the BusyAction property (of the object owning the
  interrupting callback) determines if MATLAB enqueues or discards the interrupting
  callback. A value of 'queue' allows the interrupting callback to execute after the
  running callback finishes execution. A value of 'cancel' discards the interrupting
  callback. The default value is 'queue'.

Callback Behavior When Interruption is Allowed

When an object’s Interruptible property is set to 'on', its callback can be interrupted at

the next occurrence of one of these commands: drawnow, figure, getframe, waitfor,

or pause.