This document tells you how you can design character-based user interfaces that make user interaction with the application simple and flexible.
The following topics are covered:
Using the system variable *CURS-FIELD
together with the system function POS(field-name),
you can define processing based on the field where the cursor is positioned at
the time the user presses Enter.
*CURS-FIELD contains the internal
identification of the field where the cursor is currently positioned; it cannot
be used by itself, but only in conjunction with
POS(field-name).
You can use *CURS-FIELD and
POS(field-name), for example, to enable
a user to select a function simply by placing the cursor on a specific field
and pressing Enter.
The example below illustrates such an application:
DEFINE DATA LOCAL
1 #EMP (A1)
1 #CAR (A1)
1 #CODE (N1)
END-DEFINE
*
INPUT USING MAP 'CURS'
*
DECIDE FOR FIRST CONDITION
WHEN *CURS-FIELD = POS(#EMP) OR #EMP = 'X' OR #CODE = 1
FETCH 'LISTEMP'
WHEN *CURS-FIELD = POS(#CAR) OR #CAR = 'X' OR #CODE = 2
FETCH 'LISTCAR'
WHEN NONE
REINPUT 'PLEASE MAKE A VALID SELECTION'
END-DECIDE
END
And the result:
SAMPLE MAP
Please select a function
1.) Employee information _
2.) Vehicle information _ <== Cursor positioned
on field
Enter code: _
To select a function, do one of the following:
- place the cursor on the input field next to desired function and press Enter
- mark the input field next to desired function with an X and press Enter
- enter the desired function code (1 or 2) in the 'Enter code' field and press
Enter
|
If the user places the cursor on the input field (#EMP)
next to Employee information, and presses Enter, the program LISTEMP
displays a list of employee names:
Page 1 2001-01-22 09:39:32
NAME
--------------------
ABELLAN
ACHIESON
ADAM
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
AECKERLE
AFANASSIEV
AFANASSIEV
AHL
AKROYD
|
Notes:
*CURS-FIELD identifies the operand that represents
the value of the control that has the input focus. You may use
*CURS-FIELD in conjunction with the
POS function to check for the control that has the input focus and
perform processing depending on that condition.
*CURS-FIELD
and POS(field-name) serve for internal
identification of the fields only. They cannot be used for arithmetical
operations.
The Natural system function POS(field-name)
contains the internal identification of the field whose name is specified with
the system function.
POS(field-name) may be used to
identify a specific field, regardless of its position in a map. This means that
the sequence and number of fields in a map may be changed, but
POS(field-name) will still uniquely
identify the same field. With this, for example, you need only a single
REINPUT statement to
make the field to be MARKed dependent on the program logic.
Note:
The value POS(field-name)
serves for internal identification of the fields only. It cannot be used for
arithmetical operations.
Example:
...
DECIDE ON FIRST VALUE OF ...
VALUE ...
COMPUTE #FIELDX = POS(FIELD1)
VALUE ...
COMPUTE #FIELDX = POS(FIELD2)
...
END-DECIDE
...
REINPUT ... MARK #FIELDX
...
Full details on *CURS-FIELD
and POS(field-name)
are described in the System Variables and System
Functions documentation.
Using the system variable *CURS-LINE,
you can make processing dependent on the line where the cursor is positioned at
the time the user presses Enter.
Using this variable, you can make user-friendly menus. With the appropriate programming, the user merely has to place the cursor on the line of the desired menu option and press Enter to execute the option.
The cursor position is defined within the current active window, regardless of its physical placement on the screen.
Note:
The message line, function-key lines and statistics line/infoline
are not counted as data lines on the screen.
The example below demonstrates line-sensitive processing using the
*CURS-LINE
system variable. When the user presses Enter on the map, the program
checks if the cursor is positioned on line 8 of the screen which contains the
option Employee information. If this is the case, the program that
lists the names of employees LISTEMP is executed.
DEFINE DATA LOCAL
1 #EMP (A1)
1 #CAR (A1)
1 #CODE (N1)
END-DEFINE
*
INPUT USING MAP 'CURS'
*
DECIDE FOR FIRST CONDITION
WHEN *CURS-LINE = 8
FETCH 'LISTEMP'
WHEN NONE
REINPUT 'PLACE CURSOR ON LINE OF OPTION YOU WISH TO SELECT'
END-DECIDE
END
Output:
Company Information
Please select a function
[] 1.) Employee information
2.) Vehicle information
Place the cursor on the line of the option you wish to select and press
Enter |
The user places the cursor indicated by square brackets [] on the line of the desired option and presses Enter and the corresponding program is executed.
The system variable *CURS-COL
can be used in a similar way to *CURS-LINE
described above. With *CURS-COL you can make
processing dependent on the column where the cursor is positioned on the
screen.
Frequently you may wish to make processing dependent on the function key a user presses.
This is achieved with the statement SET KEY, the system variable
*PF-KEY
and a modification of the default map settings (Standard Keys =
Y).
The SET KEY statement assigns functions to function keys
during program execution. The system variable
*PF-KEY contains the identification of the last
function key the user pressed.
The example below illustrates the use of SET KEY in
combination with *PF-KEY.
... SET KEY PF1 * INPUT USING MAP 'DEMO&' IF *PF-KEY = 'PF1' WRITE 'Help is currently not active' END-IF ...
The SET KEY statement activates PF1 as a
function key.
The IF statement defines what action is to be taken when
the user presses PF1. The system variable
*PF-KEY is checked for its current content; if it
contains PF1, the corresponding action is taken.
Further details regarding the statement
SET KEY and the system
variable *PF-KEY
are described in the Statements and the System
Variables documentation respectively.
When defining processing based on function keys, further comfort can be
added by using the system variable *PF-NAME.
With this variable you can make processing dependent on the name of a function,
not on a specific key.
The variable *PF-NAME contains the name of
the last function key the user pressed (that is, the name as assigned to the
key with the NAMED clause of
the SET KEY
statement).
For example, if you wish to allow users to invoke help by pressing
either PF3 or PF12, you assign the same name (in the
example below: INFO) to both keys. When the user presses either
one of the keys, the processing defined in the IF statement is performed.
...
SET KEY PF3 NAMED 'INFO'
PF12 NAMED 'INFO'
INPUT USING MAP 'DEMO&'
IF *PF-NAME = 'INFO'
WRITE 'Help is currently not active'
END-IF
...
The function names defined with NAMED appear in the
function-key lines:
Below is information on:
As stated in the section Screen Design - Windows, only one window is active at any one time. This normally means that input is only possible within that particular window.
Using the *COM system
variable, which can be regarded as a communication area, it is possible to
enter data outside the current window.
The prerequisite is that a map contains
*COM as a modifiable field. This field is then
available for the user to enter data when a window is currently on the screen.
Further processing can then be made dependent on the content of
*COM.
This allows you to implement user interfaces as already used, for example, by Con-nect, Software AG's office system, where a user can always enter data in the command line, even when a window with its own input fields is active.
Note that *COM is only cleared when the
Natural session is ended.
In the example below, the program ADD performs a simple addition using
the input data from a map. In this map, *COM has
been defined as a modifiable field (at the bottom of the map) with the length
specified in the AL field of the Extended
Field Editing. The result of the calculation is displayed in a
window. Although this window offers no possibility for input, the user can
still use the *COM field in the map outside the
window.
DEFINE DATA LOCAL
1 #VALUE1 (N4)
1 #VALUE2 (N4)
1 #SUM3 (N8)
END-DEFINE
*
DEFINE WINDOW EMP
SIZE 8*17
BASE 10/2
TITLE 'Total of Add'
CONTROL SCREEN
FRAMED POSITION SYMBOL BOT LEFT
*
INPUT USING MAP 'WINDOW'
*
COMPUTE #SUM3 = #VALUE1 + #VALUE2
*
SET WINDOW 'EMP'
INPUT (AD=O) / 'Value 1 +' /
'Value 2 =' //
' ' #SUM3
*
IF *COM = 'M'
FETCH 'MULTIPLY' #VALUE1 #VALUE2
END-IF
END
Output of Program ADD:
Map to Demonstrate Windows with *COM
CALCULATOR
Enter values you wish to calculate
Value 1: 12__
Value 2: 12__
+-Total of Add-+
! !
! Value 1 + !
! Value 2 = !
! !
! 24 !
! !
+--------------+
Next line is input field (*COM) for input outside the window:
|
In this example, by entering the value M, the user
initiates a multiplication function; the two values from the input map are
multiplied and the result is displayed in a second window:
Map to Demonstrate Windows with *COM
CALCULATOR
Enter values you wish to calculate
Value 1: 12__
Value 2: 12__
+-Total of Add-+ +--------------+
! ! ! !
! Value 1 + ! ! Value 1 x !
! Value 2 = ! ! Value 2 = !
! ! ! !
! 24 ! ! 144 !
! ! ! !
+--------------+ +--------------+
Next line is input field (*COM) for input outside the window:
M
|
Normally, when a window is active and the window contains no input
fields (AD=M
or AD=A), the cursor is placed in the top left corner of
the window.
With the terminal command %T*, you can
position the cursor to a *COM system
variable outside the window when the active window contains no input
fields.
By using %T* again, you can switch back to
standard cursor placement.
Example:
...
INPUT USING MAP 'WINDOW'
*
COMPUTE #SUM3 = #VALUE1 + #VALUE2
*
SET CONTROL 'T*'
SET WINDOW 'EMP'
INPUT (AD=O) / 'Value 1 +' /
'Value 2 =' //
' ' #SUM3
...
Below is information on:
With these terminal commands, you can copy parts of a screen into the
Natural stack (%CS) or into the
system variable *COM
(%CC).
The protected data from a specific screen line are copied field by field.
The full options of these terminal commands are described in the Terminal Commands documentation.
Once copied to the stack or *COM, the
data are available for further processing. Using these commands, you can make
user-friendly interfaces as in the example below.
In the following example, the program COM1 lists all employee names from Abellan to Alestia.
DEFINE DATA LOCAL 1 EMP VIEW OF EMPLOYEES 2 NAME(A20) 2 MIDDLE-NAME (A20) 2 PERSONNEL-ID (A8) END-DEFINE * READ EMP BY NAME STARTING FROM 'ABELLAN' THRU 'ALESTIA' DISPLAY NAME END-READ FETCH 'COM2' END
Output of Program COM1:
Page 1 2006-08-12 09:41:21
NAME
--------------------
ABELLAN
ACHIESON
ADAM
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
AECKERLE
AFANASSIEV
AFANASSIEV
AHL
AKROYD
ALEMAN
ALESTIA
MORE
|
Control is now passed to the program COM2.
DEFINE DATA LOCAL 1 EMP VIEW OF EMPLOYEES 2 NAME(A20) 2 MIDDLE-NAME (A20) 2 PERSONNEL-ID (A8) 1 SELECTNAME (A20) END-DEFINE * SET KEY PF5 = '%CCC' * INPUT NO ERASE 'SELECT FIELD WITH CURSOR AND PRESS PF5' * MOVE *COM TO SELECTNAME FIND EMP WITH NAME = SELECTNAME DISPLAY NAME PERSONNEL-ID END-FIND END
In this program, the terminal command %CCC is assigned
to PF5. The terminal command copies all protected data from the line
where the cursor is positioned to the system variable
*COM. This
information is then available for further processing. This further processing
is defined in the program lines shown in boldface.
The user can now position the cursor on the name that interests him; when he/she now presses PF5, further employee information is supplied.
SELECT FIELD WITH CURSOR AND PRESS PF5 2006-08-12 09:44:25
NAME
--------------------
ABELLAN
ACHIESON
ADAM <== Cursor positioned on name for which more information is required
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
ADKINSON
AECKERLE
AFANASSIEV
AFANASSIEV
AHL
AKROYD
ALEMAN
ALESTIA
|
In this case, the personnel ID of the selected employee is displayed:
Page 1 2006-08-12 09:44:52
NAME PERSONNEL
ID
-------------------- ---------
ADAM 50005800
|
If you wish to return to and re-execute an
INPUT statement, you
use the REINPUT
statement. It is generally used to display a message indicating that the data
input as a result of the previous INPUT statement were
invalid.
If you specify the FULL option in a
REINPUT statement, the corresponding INPUT statement
will be re-executed fully:
With an ordinary REINPUT statement (without
FULL option), the contents of variables that were changed between
the INPUT and REINPUT statement will not be
displayed; that is, all variables on the screen will show the contents they had
when the INPUT statement was originally executed.
With a REINPUT
FULL statement, all changes that have been made after the
initial execution of the INPUT statement will be applied to the
INPUT statement when it is re-executed; that is, all variables on
the screen contain the values they had when the REINPUT statement
was executed.
If you wish to position the cursor to a specified field, you can use
the MARK
option, and to position to a particular position within a specified field, you
use the MARK POSITION option.
The example below illustrates the use of
REINPUT
FULL with
MARK
POSITION.
DEFINE DATA LOCAL 1 #A (A10) 1 #B (N4) 1 #C (N4) END-DEFINE * INPUT (AD=M) #A #B #C IF #A = ' ' COMPUTE #B = #B + #C RESET #C REINPUT FULL 'Enter a value' MARK POSITION 5 IN *#A END-IF END
The user enters 3 in field #B and
3 in field #C and presses Enter.
#A #B 3 #C 3 |
The program requires field #A to be non-blank. The
REINPUT FULL statement with MARK POSITION 5 IN *#A
returns the input screen; the now modified variable #B contains
the value 6 (after the COMPUTE calculation has been
performed). The cursor is positioned to the 5th position in field
#A ready for new input.
Enter name of field
#A _ #B 6 #C 0
Enter a value
|
This is the screen that would be returned by the same statement, without
the FULL option. Note that the variables #B and
#C have been reset to their status at the time of execution of the
INPUT statement (each field contains the value 3).
#A _ #B 3 #C 3 |