Restricting Actions to Certain Arguments

Restricting an action to a particular type of argument refines the action. For example, it is useful to 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.

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.
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

Restricting Actions to Certain Arguments

Technical documentation

» Table of Contents

» Index

Restricting an Action to a Specified Data Type

Restricting an Action Based on the Number of Arguments

To Provide Different Double-Click and Drop Behavior

Restricting an Action Based on the Mode of the Argument