Creating Graphical User Interfaces

Properties that Affect Callback Execution

Because callbacks execute asynchronously in response to outside events, it is impossible to predict when a callback will run or what callback may already be running. Generally speaking, MATLAB queues the callbacks that are waiting to run until the one that is running can be interrupted or finishes execution. These two properties, BusyAction and Interruptible, let you influence this process. Except as noted, the value you assign each property applies to all callbacks of the given component.

See Interrupting Executing Callbacks for more information.

BusyAction

This property determines if a component's callbacks should attempt to interrupt a previously executing callback.

• If the value is cancel, the event is discarded and the callback does not execute.
• If the value is queue, and the Interruptible property of the previously excuting callback is on, the second callback is added to the event queue and executes in its turn after the first callback finishes execution or encounters a drawnow, figure, getframe, pause, or waitfor command.

Note    If the interrupting callback is a DeleteFcn or CreateFcn callback, a figure's CloseRequest callback, or a figure, panel, or button group's ResizeFcn callback, it interrupts an executing callback regardless of the value of that component's Interruptible property.

Interruptible

This property determines whether a component's callbacks can be interrupted. If a callback is executing and the user triggers an event (such as a mouse click) on an object for which a callback is defined, that callback attempts to interrupt the first callback. MATLAB processes the callbacks according to these factors:

• The Interruptible property of the object whose callback is executing
• Whether the executing callback contains drawnow, figure, getframe, pause, or waitfor statements
• TheBusyAction property of the object whose callback is waiting to execute

If the Interruptible property of the object whose callback is executing is on (the default), the callback can be interrupted. Whenever the callback calls one of the drawnow, figure, getframe, pause, or waitfor functions, the function processes any events in the event queue, including the waiting callback, before performing its defined task.

If the Interruptible property of the object whose callback is executing is off, the callback cannot be interrupted (except by certain callbacks; see the note below). The BusyAction property of the object whose callback is waiting to execute determines what happens to its interrupting callback.

Note    If the interrupting callback is a DeleteFcn or CreateFcn callback, a figure's CloseRequest callback, or a figure, panel, or button group's ResizeFcn callback, it interrupts an executing callback regardless of the value of that component's Interruptible property.

Information About Component State

Properties that Affect Component Access

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