Dialog Callback Routines

All callback routines should have the following interface:

  SUBROUTINE callback ( dlg, control_name, callbacktype)

dlg
Refers to the dialog box and allows the callback to change values of the dialog controls.

control_name
Is the name of the control that caused the callback.

callbacktype
Indicates what callback is occurring (for example, DLG_CLICKED, DLG_CHANGE, DLG_DBLCLICK).

The last two arguments let you write a single subroutine that can be used with multiple callbacks from more than one control. Typically, you do this for controls comprising a logical group. For example, all the controls in the temperature dialog in the TEMP example are associated with the same callback routine, UpdateTemp. You can also associate more than one callback routine with the same control, but you must then provide an index parameter to indicate which callback is to be used.

The following is an example of a callback routine:

  SUBROUTINE UpdateTemp( dlg, control_name, callbacktype )
  USE DFLOGM
  IMPLICIT NONE
  TYPE (dialog) dlg
  INTEGER control_name
  INTEGER callbacktype
  INCLUDE 'RESOURCE.FD'
  CHARACTER(256) text
  INTEGER cel, far, retint
  LOGICAL retlog
! Suppress compiler warnings for unreferenced arguments.
  INTEGER local_callbacktype
  local_callbacktype = callbacktype

  SELECT CASE (control_name)
    CASE (IDC_EDIT_CELSIUS)
    ! Celsius value was modified by the user so
    ! update both Fahrenheit and Scroll bar values.
      retlog = DlgGet( dlg, IDC_EDIT_CELSIUS, text )
      READ (text, *, iostat=retint) cel
      IF ( retint .eq. 0 ) THEN
        far = (cel-0.0)*((212.0-32.0)/100.0)+32.0
        WRITE (text,*) far
        retlog = DlgSet( dlg, IDC_EDIT_FAHRENHEIT,                    &
    &                    TRIM(ADJUSTL(text)) )
        retlog = DlgSet( dlg, IDC_SCROLLBAR_TEMPERATURE, cel,         &
    &                    DLG_POSITION )
      END IF
    CASE (IDC_EDIT_FAHRENHEIT)
    ! Fahrenheit value was modified by the user so
    ! update both celsius and Scroll bar values.
       retlog = DlgGet( dlg, IDC_EDIT_FAHRENHEIT, text )
       READ (text, *, iostat=retint) far
       IF ( retint .eq. 0 ) THEN
         cel = (far-32.0)*(100.0/(212.0-32.0))+0.0
         WRITE (text,*) cel
         retlog = DlgSet( dlg, IDC_EDIT_CELSIUS, TRIM(ADJUSTL(text)) )
         retlog = DlgSet( dlg, IDC_SCROLLBAR_TEMPERATURE, cel,        &
    &                     DLG_POSITION )
       END IF
    CASE (IDC_SCROLLBAR_TEMPERATURE)
    ! Scroll bar value was modified by the user so
    ! update both Celsius and Fahrenheit values.
       retlog = DlgGet( dlg, IDC_SCROLLBAR_TEMPERATURE, cel,          &
    &                   DLG_POSITION  )
       far = (cel-0.0)*((212.0-32.0)/100.0)+32.0
       WRITE (text,*) far
       retlog = DlgSet( dlg, IDC_EDIT_FAHRENHEIT, TRIM(ADJUSTL(text)) )
       WRITE (text,*) cel
       retlog = DlgSet( dlg, IDC_EDIT_CELSIUS, TRIM(ADJUSTL(text)) )
    END SELECT
  END SUBROUTINE UpdateTemp

Each control in a dialog box, except a pushbutton, has a default callback that performs no action. The default callback for a pushbutton's click event sets the return value of the dialog to the pushbutton's name and then exits the dialog. This makes all pushbuttons exit the dialog by default, and gives the OK and CANCEL buttons good default behavior. A routine that calls DLGMODAL can then test to see which pushbutton caused the modal dialog to exit.

Callbacks for a particular control are called after the value of the control has been changed by the user's action. Calling DLGSET does not cause a callback to be called for the changing value of a control. In particular, when inside a callback, performing a DLGSET on a control will not cause the associated callback for that control to be called.

Calling DLGSET before or after DLGMODAL or DLGMODELESS has been called also does not cause the callback to be called. If the callback needs to be called, it can be called manually using CALL after the DLGSET is performed.