screen.input utility

The screen.input utility displays a formatted screen and waits for input from a user. Multiple fields can be entered by the user before validation. Type checking is done by the subroutine, and the caller can provide a custom external routine to perform additional controls.


call "dm,bp, screen.input"


The common variables defined in dm,bp,includes must be set as follows:

screen Array of up to 512 options. If MultiValued, the options are presented in a multicolumnar format, with the input field beneath the headers. Data is entered and validated when the cursor is moved out of the field with the cursor movement commands (CTRL+N: Next; CTRL+B: Back; CTRL+J: Move left; CTRL+K: Move right. CTRL+X clears an input field). Array of data. If nonnull, the data displays and can be modified by the user.
screen.type Array of type controls. Controls user input. If the corresponding screen element is MultiValued, the control applies to all MultiValues. Array of help messages. The message displays starting at the line specified by screen.msgline. A value mark is a line separator. If nonnull, the help displays starting at the line specified by screen.msgline when the cursor is moved to the corresponding option.
screen.size Number of actual entries in the screen array.
screen.title Title. Displayed underlined.
screen.x Coordinates of the upper-left corner of the menu, starting at 0,0.
screen.y Coordinates of the upper-left corner of the menu, starting at 0,0. Option number to set as active (highlighted).
screen.lastline Last line available to display the menu. If there are more options than there are available lines, the menu displays in columnar format. If there are more columns than possible to display on the 80 columns screen, only some columns are displayed.
screen.width Width of an option. The default is 35 characters.
screen.msgline Line number where the help messages can be displayed. The message area extends to the end of the screen.
screen.notice If nonnull, contains the name of an external subroutine that is called periodically. The main program can provide a polling routine to display user information or perform some periodic task.
screen.control If nonnull, contains the name of an external subroutine that performs custom controls on user input. This routine must either be cataloged in the current account, or, better, be an explicit path, such as accounting,bp, check.input.


The variables below are updated: User selection:
Q Quit or Esc.
Y Validated.
screen.maxsize Last line actually displayed on screen. In most cases, it is screen.y+screen.size. However, if there are too many options to fit in one column, this variable reflects the actual last line on screen. This is used by screen.erase.

Input Control

The screen.type array elements contain these codes:

null Optional field. Can be left empty. No control.
t Required field. Any text.
x Display only. The user is not permitted to modify the data. The cursor cannot be moved into the corresponding field.
l Explicit list. The user can enter only one of an explicit list of elements. Each element is separated by a tilde. For example: l~yes~no~. Note that a trailing tilde is required.
y Confirmation field. The user can only select [y{es}|n{o}|q{uit}]. If y is entered, the routine terminates.
n Numeric field. Followed by the min and max legal values (inclusive), separated by a dash. For example: n0-1024.
number Custom control code. This strictly positive number is passed as the first argument to the user provided external routine specified in screen.control.

Input Control Subroutine

The user can specify an external subroutine in screen.control that is called when the control code in a screen.type array element is a number. This number is passed as the first argument of the subroutine, along with other information. The subroutine can then either validate the subroutine, and/or modify the user input. The user must provide a subroutine with these arguments:

Input 1st arg Control type number.
2nd arg User input data.
3rd arg Data field to leave (the one to control).
4th arg Data field to enter (where the cursor now is).
Output 1st arg Set to 0 if data is invalid, or 1 if ok.
2nd arg Validated data, if 1st arg=1.
3rd arg Unchanged.
4th arg Unchanged.
Note: The numeric control does not allow negative numbers as part of the valid range.


The example below displays a screen like:

User : ...........
Order #1 Order #2
................ .................
include dm,bp,includes
* Init the screen
* ---------------
call "dm,bp, screen.init"
* Clear the whole screen
* ----------------------
crt @(-1)
* Build the menu
* --------------
screen.x=0 ; screen.y=0 ;* Top left corner
screen(1)="User" ;* Option 1
screen(2)<1,-1>="Order #1 " ;* 1st column
screen(2)<1,-1>="Order #2 " ;* 2nd column
screen.type(1)=’t’ ;* Mandatory text
screen.type(2)=1 ;* User provided control
mat’’ ;* Clear result"User name" ;* Help messages"Account number and val date"
screen.size=2 ;* Number of options ;* Option 1 is default
screen.msgline=23 ;* Help line
screen.control="account,bp, check.input"
* Display the screen and input data
* ---------------------------------
call "dm,bp, screen.input"
begin case
      * Back to TCL
      * User typed ’q’ or Esc
      * OK. Validated
end case