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update_proc - Set to a Tcl procedure name to be called when clicking on the 'Ok' button in the window.
delete_proc - Set to a Tcl procedure name to be called when delete the blockdata
check_values . Set to a Tcl procedure name
icon - It allows to put an image in .png format in the data tree. The image should be stored inside the images folder of the problem type. A Tcl procedure can be used to return the name at runtime.
help - It displays a pop-up window of help information related to the task the user is performing.
state - Specifies one of two states for the field: normal, or hidden. Note that hidden <container> field can be used for storing hidden values, that you do not want to show in the user interface. It also permits to handle a Tcl function, by means of square brackets.
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