XmSpinBoxValidatePosition (3)

#include <Xm/SpinBox.h>
int XmSpinBoxValidatePosition(
Widget textfield,
int *position);

The XmSpinBoxValidatePosition function is a utility that can be used by applications wanting to implement a policy for tracking user modifications to editable XmSpinBox children of type XmNUMERIC. The specifics of when and how the user's modifications take effect is left up to the application.

text_field

The text_field argument specifies the widget ID of the child of the XmSpinBox that is being modified. The requirement on text_field is that it holds the accessTextual trait (already a requirement for children of XmSpinBox). This way, XmSpinBox can extract the string out of the text_field widget (even if it is not an XmTextField).

position

The location pointed to by the position argument is assigned the result of the translation done by XmSpinBoxValidatePosition. XmSpinBoxValidatePosition first checks to make sure this is an XmNUMERIC XmSpinBox child. If it is not, XSmpinBoxValidatePosition sets position to the current position and returns XmCURRENT_VALUE.

XmSpinBoxValidatePosition attempts to translate the input string to a floating point number. If this translation fails, XmSpinBoxValidatePosition sets position to the current position and returns XmCURRENT_VALUE.

XmSpinBoxValidatePosition converts the floating point number to an integer using the XmNdecimalPoints resource. Extra decimal places are truncated. The resulting integer is range checked to make sure it falls within the valid range defined by XmNminimumValue and XmNmaximumValue inclusive. If the input falls outside this range, XmSpinBoxValidatePosition sets position to the nearest limit and returns either XmMINIMUM_VALUE or XmMAXIMUM_VALUE.

Finally, XmSpinBoxValidatePosition checks the integer to make sure it belongs to the series defined by XmNminimumValue ... XmNminimumValue + ((n - 1) * XmNincrementValue). If the integer does not belong to this series, XmSpinBoxValidatePosition sets position to the nearest element which is less than or equal to the integer and returns XmINCREMENT_VALUE.

Otherwise, XmSpinBoxValidatePosition assigns the integer to position and returns XmVALID_VALUE.

The XmSpinBoxValidatePosition function returns the status of the validation. The set of possible values returned is as follows:

XmCURRENT_VALUE

Cannot convert, returning current position_value.

XmMINIMUM_VALUE

Less than min.

XmMAXIMUM_VALUE

More than max.

XmINCREMENT_VALUE

Not on increment.

XmVALID_VALUE

Okay.

This first example demonstrates how the XmSpinBoxValidatePosition function could be used from inside an XmNmodifyVerifyCallback callback installed on the XmSpinBox or the XmSimpleSpinBox:

/*
 * Install a callback on a spin box arrow press.
 */
  XtAddCallback(sb, XmNmodifyVerifyCallback, ModifyVerifyCB, NULL);
  XtAddCallback(simple_sb, XmNmodifyVerifyCallback, ModifyVerifyCB, NULL);

with the callback doing:

void ModifyVerifyCB(widget, call_data, client_data) {
    XmSpinBoxCallbackStruct *cbs = (XmSpinBoxCallbackStruct*) call_data;
    int position;
    Widget textual = NULL;
    if (XtIsSubclass(w, xmSimpleSpinBoxWidgetClass))
    {
        Arg args[1];
        XtSetArg(args[0], XmNtextField, &textual);
        XtGetValues(w, args, 1);
    }
    else if (XtIsSubclass(w, xmSpinBoxWidgetClass))
      textual = cbs->widget;
    else
      textual = (Widget) NULL;

    ...

    if (XmSpinBoxValidatePosition(textual, &position) == XmCURRENT_VALUE)
      XBell(XtDisplay(w), 0);
    else
      cbs->position = position;
}

This second example demonstrates how the XmSpinBoxValidatePosition function could be used from inside an XmNactivateCallback callback installed on the TextField child of the XmSpinBox:

/*
 * Install a callback on a spin box arrow press.
 */
XtAddCallback(tf, XmNactivateCallback, ModifyVerifyChildCB, NULL);

with the callback doing:

void ModifyVerifyChildCB(widget, call_data, client_data) {
    int     position;
    Widget  textual = widget;
    Arg     args[1];

    if (XmSpinBoxValidatePosition (textual, &position) == XmCURRENT_VALUE)
      XBell(XtDisplay(widget), 0);

    /* Set the position constraint resource of the textfield */

    XtSetArg(args[0], XmNposition, position);
    XtSetValues(textual, args, 1);
}

XmSpinBox(3), XmCreateSpinBox(3)