Creating Graphical User Interfaces

Properties that Affect Component Access

HandleVisibility

The HandleVisibility property controls access to a component's handle. This property determines when a component's handle is accessible in its parent's list of children. When a handle is not accesible in a parent's list of children, it is not returned by functions that obtain handles by searching the object hierarchy or querying handle properties with functions such as get, findobj, gca, gcf, gco, newplot, cla, clf, and close. Neither is the handle accessible in the parent figure's CurrentObject property.

Handles that are hidden are still valid. If you know a component's handle, you can set and get its properties, and pass it to any function that operates on handles.

• Handles are always accessible when HandleVisibility is on.
• Setting HandleVisibility to callback causes handles to be accessible from within callback routines or functions invoked by callback routines, but not from within functions invoked from the command line. This provides a means to protect GUIs from command-line users, while allowing callback routines to have complete access to the handles.
• Setting HandleVisibility to off makes handles inaccessible at all times. This may be necessary when a callback routine invokes a function that might potentially damage the GUI (such as evaluating a user-typed string), and so temporarily hides its own handles during the execution of that function.

You can set the root ShowHiddenHandles property to on to make all handles accessible, regardless of their HandleVisibility settings. This does not affect the values of the HandleVisibility properties.

Properties that Affect Callback Execution

Examples of Callbacks for GUI Components

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