callback
The command procedure to be executed when the panel is activated. The window parent of panel and panel itself are passed to the procedure as parameters. When panel belongs to a table window, the row/column index of the panel is passed as a third parameter.
This element is activated for different reasons depending on the panel type:
button - On a mouse hit in the button.
check_button - On a mouse hit in the toggle button.
clock - Not applicable.
combo_box - On pressing the <return> key in the text area, or by selecting an option from the associated pulldown menu.
dial - On a mouse button-up event.
label - Not applicable.
list - On a mouse double click (or the <return> key) in the scrollable list.
log - Not applicable.
options - On a mouse hit in the options pulldown menu.
radio_box - On a mouse hit in one of the options.
sash - On mouse up after a dynamic reposition.
separator - Not applicable.
slider - On a mouse button-up event.
text - On pressing the <return> key.
window - Not applicable.
Initially, panels have a .exec procedure of null.
For button panels in a menu bar, a valid exec procedure makes the button visible. A null exec procedure makes it invisible.
panel.exec (<window>,<panel>{,<row>})
win1.panels[1].exec = { args w=window, p=panel tell <'New text input box value:',p.text> }