An additional function used for GUI programming called GUI_MAINFCN, was introduced in MATLAB 6.5 (R13). This function is used to initialize the GUI and its layout. It is also used to dispatch the GUI's callback functions. The use of GUI_MAINFCN allows the creation of two additional functions, OpeningFcn and OutputFcn, which are not part of a normal figure.
The GUI's OpeningFcn is called just before the GUI is made visible during initialization. The OpeningFcn is used for initialization commands, which would have been issued in the GUI's main function in MATLAB 6.1 and 6.0. Using the OpeningFcn makes it possible to alter a GUI before it is rendered on the screen.
The GUI's OutputFcn is used to specify the output from the GUI:
h = mygui
The default output is the handle of the GUI figure. The OutputFcn runs after the OpeningFcn has completed execution and the figure is made visible. If the WAITFOR or UIWAIT functions are used to block execution of the OpeningFcn, then the OutputFcn will be run after the call to WAITFOR has returned. For information on WAITFOR or UIWAIT refer to the documentation by typing:
doc waitfor
or
doc uiwait
at the MATLAB command prompt.
