Restricting Actions to Certain Arguments

Restricting an action to a particular type of argument refines the action. For example, you should restrict an action that invokes a viewer for PostScript files to only PostScript file arguments; with the restriction, the action will return an error dialog if a non-PostScript file is specified.

You can restrict actions based on:

• The data type of the file argument.

• The number of file arguments—for example, no arguments versus one or more arguments. This provides different drop and double-click behavior for the action icon.

• The read/write mode of the argument.

Restricting an Action to a Specified Data Type

Use the ARG_TYPE field to specify the data types for which the action is valid. Use the data attribute name.

You can enter a list of data types; separate the entries with commas.

For example, the following action definition assumes a GIF data type has been created.

ACTION Open_Gif
 {
 	TYPE					COMMAND
 	LABEL					"Display Gif"
 	WINDOW_TYPE			NO_STDIO
 	ARG_TYPE				Gif
 	ICON					xgif
 	DESCRIPTION			Displays gif files
 	EXEC_STRING			xgif
 }

Restricting an Action Based on the Number of Arguments

Use the ARG_COUNT field to specify the number of arguments the action can accept. Valid values are:

* (Default)—any number of arguments. Other values have precedence over *.

n—any non-negative integer, including 0.

>n—more than n arguments.

<n—fewer than n arguments.

One use for ARG_COUNT is to provide different action icon behavior, depending on whether the user double-clicks the icon or drops a file on it. See the next section, “To Provide Different Double-Click and Drop Behavior.”

To Provide Different Double-Click and Drop Behavior

Use this procedure to create an action that accepts a dropped file but does not prompt for a file when the action icon is double-clicked.

1. Create an action definition for the double-click functionality.

   Use the ARG_COUNT field to specify 0 arguments. Use a syntax for the EXEC_STRING that does not accept a dropped argument.

2. Create a second action definition for the drop functionality.

   Use the ARG_COUNT field to specify >0 argument. Use a syntax for the EXEC_STRING that accepts a dropped file.

   For example, suppose the following two command lines can be used to start an editor named vedit:

   • To start the editor with no file argument:

     	vedit

   • To start the editor with a file argument that is opened as a read-only document:

     	vedit -R filename
     

     The following two actions create drop and double-click functionality for an action named Vedit. The first action has precedence when the database is searched for a match, since ARG_COUNT 0 is more specific than the implied ARG_COUNT * of the drop functionality definition.

     # Double-click functionality
      ACTION Vedit
      {
      	TYPE						COMMAND
      	ARG_COUNT				0
      	WINDOW_TYPE				PERM_TERMINAL
      	EXEC_STRING				vedit
      }
     
      # Drop functionality
      ACTION Vedit
      {
      	TYPE						COMMAND
      	WINDOW_TYPE				PERM_TERMINAL
      	EXEC_STRING				vedit -R %Arg_1%
      }

Restricting an Action Based on the Mode of the Argument

Use the ARG_MODE field to specify the read/write mode of the argument. Valid values are:

* (Default)—any mode

!w—non-writable

w—writable