Key

A scalar string containing the name of a function key to be programmed. IDL maintains an internal list of function key names and the escape sequences they send.

• UNIX: Under UNIX, DEFINE_KEY allows you to set the values of two distinctly different types of keys:
• Control characters: Any of the 26 control characters (Ctrl+A through Ctrl+Z) can be associated with specific actions by specifying the CONTROL keyword. Control characters are the unprintable ASCII characters at the beginning of the ASCII character set. They are usually entered by holding down the Control key while the corresponding letter key is pressed.
• Function keys: Most terminals (and terminal emulators) send escape sequences when a function key is pressed. An escape sequence is a sequence of characters starting the ASCII Escape character. Escape sequences follow strict rules that allow applications such as IDL to determine when the sequence is complete. For instance, the left arrow key on most machines sends the sequence <esc>[D. The available function keys and the escape sequences they send vary from keyboard to keyboard; IDL cannot be built to recognize all of the different keyboards in existence. The ESCAPE keyword allows you to program IDL with the escape sequences for your keyboard. When you press the function key, IDL will recognize the sequence and take the appropriate action.
• UNIX: Under Unix, if Key is not already on IDL's internal list, you must use the ESCAPE keyword to specify the escape sequence, otherwise, Key alone will suffice. The available function keys and the escape sequences they send vary from keyboard to keyboard. The SETUP_KEYS procedure should be used once at the beginning of the session to enter the keys for the current keyboard. Standard Key Definitions for Unix describes the standard key definitions.

• Standard Key Definitions for Unix

Editing Key	Function
Ctrl+A	Move cursor to start of line
Ctrl+B	Move cursor left one word
Ctrl+D	EOF if current line is empty, EOL otherwise
Ctrl+E	Move to end of line
Ctrl+F	Move cursor right one word
Ctrl+K	Erase from the cursor to the end of the line
Ctrl+N	Move back one line in the recall buffer
Ctrl+R	Retype current line
Ctrl+U	Delete from current position to start of line
Ctrl+W	Delete previous word
Ctrl+X	Delete current character
Backspace, Delete	Delete previous character
ESC-I	Overstrike/insert toggle
ESC-Delete	Delete previous word
Up Arrow	Move back one line in the recall buffer
Down Arrow	Move forward one line in the recall buffer
Left Arrow	Move left one character
Right Arrow	Move right one character
R13	Move cursor left one word (Sun keyboards)
R15	Move cursor right one word (Sun keyboards)
^ text ·	Recall the first line containing text . If text is blank, recall the previous line
Other Characters ·	Insert character at the current cursor position

• VMS: Under VMS, the key names are those defined by the Screen Management utility (SMG). VMS Line Editing Keys describes some of these keys. For a complete description, refer to the VMS RTL Screen Management (SMG$) Manual .

• VMS Line Editing Keys

Key Name	Description
DELETE	Delete previous character.
PF1	Recall most recent command that matches supplied string.
PF2--PF4	Top row of keypad.
KP0--KP9	Keypad keys 0 through 9
ENTER	Keypad ENTER key
MINUS	Keypad "-" key
COMMA	Keypad "," key
PERIOD	Keypad "." key
FIND	Editing keypad FIND key
INSERT_HERE	Editing keypad INSERT HERE key
REMOVE	Editing keypad REMOVE key
SELECT	Editing keypad SELECT key
PREV_SCREEN	Editing keypad PREV_SCREEN key
NEXT_SCREEN	Editing keypad NEXT_SCREEN key

• Windows: Under Windows, function keys F2, F4, F11, and F12 can be customized.

In IDL for Windows, three special variables can be used to expand the current mouse selection, the current line, or the current filename into the output of defined keys.

For example, to define F2 as a key that executes an IDL PRINT command with the current mouse selection as its argument, use the command:

DEFINE_KEY, 'F2', 'PRINT, "%S"'

Dragging the mouse over any text in an IDL Editor or Output Log window and pressing F1 causes the selected text to be printed. The %l and %f variables can be used in a similar fashion.

• Macintosh: DEFINE_KEY does not currently work with IDL for Macintosh .

Value

The scalar string that will be printed (as if it had been typed manually at the keyboard) when Key is pressed. If Value is not present, and no function is specified for the key with one of the keywords, the key is cleared so that nothing happens when it is pressed.

MATCH_PREVIOUS

Set this keyword to program Key to prompt the user for a string, and then search the saved command buffer for the most recently issued command that contains that string. If a match is found, the matching command becomes the current command, otherwise the last command entered is used. Under Unix, the default match key is the up caret "^" key when pressed in column 1. Under VMS, the default match key is PF1.

NOECHO

Set this keyword to enter the Value assigned to Key when pressed, without echoing the string to the screen. This feature is useful for defining keys that perform such actions as erasing the screen. If NOECHO is set, TERMINATE is also assumed to be set.

TERMINATE

If this keyword is set, and Value is present, pressing Key terminates the current input operation after its assigned value is entered. Essentially, an implicit carriage return is added to the end of Value .

BACK_CHARACTER

Set this keyword to program Key to move the current cursor position left one character.

BACK_WORD

Set this keyword to program Key to move the current cursor position left one word.

CONTROL

Set this keyword to indicate that Key is the name of a control key. The default is for Key to define a function key escape sequence. To view the names used by IDL for the control keys, type the following at the Command Input Line:

HELP, /ALL_KEYS

CAUTION: The CONTROL and ESCAPE keywords are mutually exclusive and cannot be specified together.

DELETE_CHARACTER

Set this keyword to program Key to delete the character to the left of the cursor.

DELETE_CURRENT

Set this keyword to program Key to delete the character directly underneath the cursor.

DELETE_EOL

Set this keyword to program Key to delete from the cursor position to the end of the line.

DELETE_LINE

Set this keyword to program Key to delete all characters to the left of the cursor.

DELETE_WORD

Set this keyword to programs Key to delete the word to the left of the cursor.

END_OF_LINE

Set this keyword to program Key to move the cursor to the end of the line.

END_OF_FILE

Set this keyword to program Key to exit IDL if the current line is empty, and to end the current input line if the current line is not empty.

ENTER_LINE

Set this keyword to program Key to enter the current line (i.e., the action normally performed by the "Return" key).

ESCAPE

A scalar string that specifies the escape sequence that corresponds to Key . See Defining New Function Keys for further details.

CAUTION: The CONTROL and ESCAPE keywords are mutually exclusive and cannot be specified together.

FORWARD_CHARACTER

Set this keyword to program Key to move the current cursor position right one character.

FORWARD_WORD

Set this keyword to program Key to move the current cursor position right one word.

INSERT_OVERSTRIKE_TOGGLE

Set this keyword to program Key to toggle between "insert" and "overstrike" mode. When characters are typed into the middle of a line, insert mode causes the trailing characters to be moved to the right to make room for the new ones. Overstrike mode causes the new characters to overwrite the existing ones.

NEXT_LINE

Set this keyword to program Key to move forward one command in the saved command buffer and make that command the current one.

PREVIOUS_LINE

Set this keyword to program Key to move back one command in the saved command buffer and make that command the current one.

RECALL

Set this keyword to program Key to prompt the user for a command number. The saved command corresponding to the entered number becomes the current command. In order to view the currently saved commands and the number currently associated with each, enter the IDL command:

HELP, /RECALL COMMANDS

• The RECALL operation remembers the last command number entered, and if the user simply presses return, it recalls the command currently associated with that saved number. Since the number associated with a given command increases by one each time a new command is saved, this feature can be used to quickly replay a sequence of commands.

IDL> PRINT, 1

1

IDL> PRINT, 2

2

IDL> HELP, /RECALL_COMMANDS

Recall buffer length: 20

1               PRINT, 2

2               PRINT, 1

IDL> ; User presses key tied to RECALL.

Recall Line #: 2 ; Line 2 is requested.

IDL> PRINT, 1 ; Saved command 2 is recalled.

1

Recall Line #: ; User presses return.

IDL> PRINT, 2 ; Saved command 2 is recalled again.

2

REDRAW

Set this keyword to program Key to retype the current line.

START_OF_LINE

Set this keyword to program Key to move the cursor to the start of the line.