add_command name onval offval command
This adds a new command to an application. The name should be the menu pathname followed by fullstop followed by the name of the command to appear in the menu. So if the command is within a cascading menu the name will have several components broken down by fullstops, ending in the command name itself.
The onval and offval arguments control the states for which the command is to be enabled in.
The command argument is the command to execute when this menu item is
selected. This is a single argument so Tcl quoting rules must be obeyed for
multi-word commands. This command is evaluated (using the Tcl eval
command) at the time of selecting the menu item. If the command is to contain
references to variables, it is important to distinguish between variables
expanded at the time of creating the menu item and the time of executing the
menu item by backslashing the latter.
For example, the Gap4 "Quality" mode of the consensus output has the following specification.
add_command {File.Calculate a consensus.quality} 8 10 {QualityDialog \$io}
Here the "quality" command is within the "Calculate a consensus" cascading
menu which is within the "File" menu. It is enabled by bit 3 (a database
containing data has been opened) and is disabled by bits 1 and 3 (the database
has no data or busy mode is enabled). The command to run is
QualityDialog $io. If we did not backslash the $io in this
command the io variable would be expanded up at the time of creating the
menus, say to "0". Then when the menu item is selected we would always execute
QualityDialog 0 which is not the desired effect.