Immediate detection of user changes

This section describes the dialogtouched predefined action.

Purpose of the dialogtouched action

The dialogtouched predefined action is a special action that can be used to detect user changes immediately without leaving the current field.

The event is trapped with an ON ACTION dialogtouched block, to execute code in your program.

Important: The dialogtouched action must be enabled/disabled in accordance with the needs of the dialog: When this action is enabled, the ON ACTION dialogtouched block will be invoked each time the user types characters, modifies the value with copy/paste actions, or uses the widget input helper (like the calendar of a DATEEDIT). In client/server mode, this can generate more network traffic as needed. As soon as the dialogtouched action is fired, it should be disabled to avoid un-necessary network round-trips, and it should only be re-enabled when needed.

When the form item type allows value changes to be detected immediately, for example with COMBOBOX, CHECKBOX or DATEEDIT fields, the alternative to dialogtouched to detect field input changes is to use the ON CHANGE trigger.

Typical usage of dialogtouched action

Singular interactive instructions are typically ended with an accept or cancel action. For example, a singular INPUT statement allows the end user to enter a database record, and validate or cancel the changes. The INPUT statement is then re-executed, to enter or modify another record.

Unlike singular dialogs, the DIALOG instruction can be used continuously for several data operations, such as navigation, creation, or modification. Typically, the default is the navigation mode, and as soon as the user starts to modify a field, it switches to edit mode, to modify a record, or create a new record. Only a user-defined close or exit action will terminate a DIALOG block. In such case, the dialog must be notified when the user starts to modify the current record. This can be achieved with the dialogtouched predefined action.

What user events fire a dialogtouched action?

The dialogtouched action works for any field controlled by the current interactive instruction, and with any type of form field.

Every time the user modifies the value of a field (without leaving the field), the ON ACTION dialogtouched block will be executed, if it is enabled.

The dialogtouched action can be triggered by typing characters in a text editor field, using copy/paste, clicking on a CHECKBOX / RADIOGROUP, moving the cursor of a SLIDER or changing a date with the calendar of a DATEEDIT.

Field value validation when dialogtouched occurs

When a dialogtouched action occurs, the current field may contain some text that does not represent a correct value corresponding to the field data type. For example, a form field bound to a DATE variable may contain only a part of a valid date string, such as "12/24/". For this reason, the target variable bound to the field cannot hold the current text displayed on the screen when the ON ACTION dialogtouched code is executed, even when using the UNBUFFERED mode.

To avoid data validation on action code execution, the dialogtouched action is defined with validate="no" attribute in the $FGLDIR/lib/default.4ad action defaults file. This is mandatory when using the UNBUFFERED mode; otherwise the runtime would try to copy the input buffer into the program variable when a dialogtouched action is invoked.

Note: Do not define validate="yes" for the dialogtouched action, otherwise non-string data fields will in most cases produce a conversion error, when the user enters data.

Programming steps to handle a "save" button

By default, the dialogtouched action and navigation actions are enabled.

In the ON ACTION dialogtouched block, detect the beginning of a record modification in a DIALOG block.

To prevent further dialogtouched action events, disable the action with a DIALOG.setActionActive() method, disable also navigation actions, and enable the save action.

Set a flag/status variable to track that the dialog is in edit mode.

When user input is validated and committed in the database, the dialogtouched and navigation actions can be enabled again, and the save action can be disabled.

Set a flag/status variable to indicate that the dialog is back to navigation mode.

In the action handler for the close or exit action, which can be used to close the form, check the status flag to know if the user has started to edit the fields, and show a warning box before leaving the dialog with EXIT DIALOG.

Code example:


   ON ACTION dialogtouched 
      CALL setup_dialog(DIALOG,TRUE)
   ON ACTION save 
      CALL save_record()
      CALL setup_dialog(DIALOG,FALSE)

   ON ACTION close
      IF NOT check_close(DIALOG) THEN
      END IF
FUNCTION setup_dialog(d,e)
   DEFINE d ui.Dialog, e BOOLEAN
   LET editing = e
   CALL DIALOG.setActionActive("dialogtouched", NOT editing)
   CALL DIALOG.setActionActive("save", editing)
   CALL DIALOG.setActionActive("query", NOT editing)

FUNCTION check_close(d)
    DEFINE d ui.Dialog
    IF editing THEN
       CALL setup_dialog(d,editing)
       RETURN mbox_yn("Do you want to close the form without saving changes?")
    END IF