# Keyboard Independence
Updated: 8/3/2020, 5:48:21 PM
Created: 8/3/2020, 5:48:21 PM
Last Updated By: Patrick Payne
Read Time: 3 minute(s)
Keyboard input can be handled independently of the current terminal type within end user coded routines by using the jBASE Command Key subroutines supplied in the jBASE libutils library.
The jBASE supplied includes, JBC.h and jCmdKeys.h, and the subroutines JBASECommandInit and JBASECommandNext (jBASE 4.1 and later) or CommandInit and CommandNext (jBASE 3.x) are integral to using this feature. The JBASECommandInit subroutine initializes the keyboard mappings while the JBASEComandNext subroutine would be used in place of the INPUT statement to return the actual command (i.e. Page Up, Insert Line, Cursor Left, etc). It is then up to the application to provide the appropriate functionality for each command.
Many of the commands returned by the JBASECommandNext subroutine are taken from default command keys used with the JED editor. The .jedrc file can be configured to alter the default definitions. Be aware that modifying .jedrcwill also change the corresponding behavior in JED.
Required Includes: JBC.h jCmdKeys.h
On jBASE 3.x the required subroutines are: CommandInit CommandNext(KeyDescriptionCode, KeyData, Timeout)
On jBASE 4.x (and later) the required subroutines are: JBASECommandInit JBASECommandNext(KeyDescriptionCode, KeyData, Timeout)
First add the following lines to the initialization of your program:
$INCLUDE JBC.h $INCLUDE jCmdKeys.h * Initialize keyboard mappings CALL JBASECommandInit * CALL CommandInit on jBASE 3.x
Then to check the keyboard for input (or window resizing etc.):
CALL JBASECommandNext(KeyDescriptionCode,KeyData,Timeout) * CALL CommandNext(KeyDescriptionCode,KeyData,Timeout) on jBASE 3.x
KeyDescriptionCodeThis variable is returned by the JBASECommandNext subroutine. The jCmdKeys.h file contains a list of equates for this description e.g. if Page Up was pressed the code returned will be 30 (i.e. cmd_scroll_up_page) and if a Alpha/Numeric key was pressed then the code returned will be 101 (i.e. cmd_alpha_numeric). If the timeout occurs before a key is pressed then the code returned will be 102 (i.e. cmd_timeout). Refer to jCmdKeys.h for a complete list of codes and their descriptions.
KeyData This is the actual code sequence that has been typed as defined in jCmdKeys.h or the ASCII code of the Alpha/Numeric key pressed. Note that all keyboard input is echoed to the screen. For this reason it is advisable to use ECHO OFF before the CALL to the JBASECommandNext routine and ECHO ON after (see EXAMPLE below).
Timeout This is a variable that is passed to the JBASECommandNext subroutine. It must be an integer indicating the number of tenths of seconds to wait until the JBASECommandNext subroutine terminates, so 150 will be a 15 second timeout. To inhibit the timeout feature initialize this variable to zero (ie Timeout = 0).
This code shows how to use the timeout capability:
$INCLUDE JBC.h $INCLUDE jCmdKeys.h EQU Timeout TO 100 ;* 10 seconds CALL JBASECommandInit * Accept keyboard input until ESC is pressed or the Timeout limit has been reached LOOP ECHO OFF CALL JBASECommandNext(RtnNo, KeyData, Timeout) ECHO ON CRT @(0):@(-4):'KeyDescriptionCode=':RtnNo:' KeyData=':KeyData: UNTIL RtnNo = cmd_escape OR RtnNo = cmd_timeout DO REPEAT CRT
The following program can be used to determine the exact KeyDescriptionCode and KeyData returned for various keyboard commands:
$INCLUDE JBC.h $INCLUDE jCmdKeys.h EQU Timeout TO 300; * 30 Seconds CALL JBASECommandInit Line = "" LOOP ECHO OFF CALL JBASECommandNext(RtnNo, KeyData, Timeout) ECHO ON UNTIL RtnNo = cmd_escape DO BEGIN CASE CASE RtnNo = cmd_alpha_numeric ;* Simple alpha-numeric Line := KeyData GOSUB CursorRight CASE RtnNo = cmd_carriage_return ;* Enter key pressed GOSUB ProcessLine CASE RtnNo = cmd_clear_end_line ;* Clear to end of line CRT @(-4): CASE RtnNo = cmd_insert_value ;* Insert a char(253) Line := @VM GOSUB CursorRight CASE RtnNo = cmd_cursor_up ;* Move cursor up a line GOSUB CursorUp CASE RtnNo = cmd_cursor_down ;* Move cursor down a line GOSUB CursorDown CASE RtnNo = cmd_cursor_right ;* Move cursor to the right GOSUB CursorRight CASE RtnNo = cmd_cursor_left ;* Move cursor to the left GOSUB CursorLeft CASE RtnNo = cmd_error ;* Unknown command string GOSUB InputError CASE RtnNo = cmd_timeout ;* The input timed out GOSUB CheckStatus CASE RtnNo = cmd_winsize ;* Size of the X window changed. GOSUB RefreshScreen CASE 1 GOSUB InputError END CASE REPEAT
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