Function EntryUpdateScrollbar

micropolis-activity/src/tk/tkentry.c:1601–1639

(entryPtr)

 *
 * EntryUpdateScrollbar --
 *
 *	This procedure is invoked whenever information has changed in
 *	an entry in a way that would invalidate a scrollbar display.
 *	If there is an associated scrollbar, then this command updates
 *	it by invoking a Tcl command.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	A Tcl command is invoked, and an additional command may be
 *	invoked to process errors in the command.
 *
 *----------------------------------------------------------------------
 */

static void
EntryUpdateScrollbar(entryPtr)
    register Entry *entryPtr;		/* Information about widget. */
{
    char args[100];
    int result, last, charsInWindow, endX;

    if (entryPtr->scrollCmd == NULL) {
	return;
    }

    /*
     * The most painful part here is guessing how many characters
     * actually fit in the window.  This is only an estimate in the
     * case where the window isn't completely filled with characters.
     */

    charsInWindow = TkMeasureChars(entryPtr->fontPtr,
	    entryPtr->string + entryPtr->leftIndex,
	    entryPtr->numChars - entryPtr->leftIndex, entryPtr->offset,
	    Tk_Width(entryPtr->tkwin),
	    TK_AT_LEAST_ONE|TK_NEWLINES_NOT_SPECIAL, &endX);
    if (charsInWindow == 0) {
	last = entryPtr->leftIndex;
    } else {
	last = entryPtr->leftIndex + charsInWindow - 1;