165) How do I create a "busy working cursor"?

Answer: - in Baudouin's code (following), the idea is to keep in an array an
up-to-date list of all shells used in the application, and set for all of them
the cursor to a watch or to the default cursor, with the 2 functions provided.

- in Dan Heller's code (later), the idea is to turn on the watch cursor for
the top-level shell only, popup a working window to possibly abort the
callback, and manage some expose events during the callback.

- in the FAQ for comp.windows.x (#113), the idea is to bring a large window on
top of the application, hide all windows below it, and turn on the watch
cursor on this large window. Unmapping the large window resets the default
cursor, mapping it turns on the watch cursor.

From Baudouin Raoult (mab@ecmwf.co.uk)

void my_SetWatchCursor(w)
Widget w;
{
        static Cursor watch = NULL;

        if(!watch)
                watch = XCreateFontCursor(XtDisplay(w),XC_watch);

        XDefineCursor(XtDisplay(w),XtWindow(w),watch);
        XmUpdateDisplay(w);
}

void my_ResetCursor(w)
Widget w;
{
        XUndefineCursor(XtDisplay(w),XtWindow(w));
        XmUpdateDisplay(w);
}


Answer: A solution with lots of bells and whistles is

/* Written by Dan Heller.  Copyright 1991, O'Reilly && Associates.
 * This program is freely distributable without licensing fees and
 * is provided without guarantee or warrantee expressed or implied.
 * This program is -not- in the public domain.
 */

/* busy.c -- demonstrate how to use a WorkingDialog and to process
 * only "important" events.  e.g., those that may interrupt the
 * task or to repaint widgets for exposure.  Set up a simple shell
 * and a widget that, when pressed, immediately goes into its own
 * loop.  First, "lock" the shell so that a timeout cursor is set on
 * the shell and pop up a WorkingDialog.  Then enter loop ... sleep
 * for one second ten times, checking between each interval to see
 * if the user clicked the Stop button or if any widgets need to be
 * refreshed.  Ignore all other events.
 *
 * main() and get_busy() are stubs that would be replaced by a real
 * application; all other functions can be used "as is."
 */
#include <Xm/MessageB.h>
#include <Xm/PushB.h>
#include <X11/cursorfont.h>

Widget shell;
void TimeoutCursors();
Boolean CheckForInterrupt();

main(argc, argv)
int argc;
char *argv[];
{
    XtAppContext app;
    Widget button;
    XmString label;
    void get_busy();

    shell = XtVaAppInitialize(&app, "Demos",
        NULL, 0, &argc, argv, NULL, NULL);

    label = XmStringCreateSimple(
        "Boy, is *this* going to take a long time.");
    button = XtVaCreateManagedWidget("button",
        xmPushButtonWidgetClass, shell,
        XmNlabelString,          label,
        NULL);
    XmStringFree(label);
    XtAddCallback(button, XmNactivateCallback, get_busy, argv[1]);

    XtRealizeWidget(shell);
    XtAppMainLoop(app);
}

void
get_busy(widget)
Widget widget;
{
    int n;

    TimeoutCursors(True, True);
    for (n = 0; n < 10; n++) {
        sleep(1);
        if (CheckForInterrupt()) {
            puts("Interrupt!");
            break;
        }
    }
    if (n == 10)
        puts("done.");
    TimeoutCursors(False, NULL);
}

/* The interesting part of the program -- extract and use at will */
static Boolean stopped;  /* True when user wants to stop processing */
static Widget dialog;    /* WorkingDialog displayed when timed out */

/* timeout_cursors() turns on the "watch" cursor over the application
 * to provide feedback for the user that he's going to be waiting
 * a while before he can interact with the appliation again.
 */
void
TimeoutCursors(on, interruptable)
int on, interruptable;
{
    static int locked;
    static Cursor cursor;
    extern Widget shell;
    XSetWindowAttributes attrs;
    Display *dpy = XtDisplay(shell);
    XEvent event;
    Arg args[1];
    XmString str;
    extern void stop();

    /* "locked" keeps track if we've already called the function.
     * This allows recursion and is necessary for most situations.
     */
    on? locked++ : locked--;
    if (locked > 1 || locked == 1 && on == 0)
        return; /* already locked and we're not unlocking */

    stopped = False; /* doesn't matter at this point; initialize */
    if (!cursor) /* make sure the timeout cursor is initialized */
        cursor = XCreateFontCursor(dpy, XC_watch);

    /* if "on" is true, then turn on watch cursor, otherwise, return
     * the shell's cursor to normal.
     */
    attrs.cursor = on? cursor : None;

    /* change the main application shell's cursor to be the timeout
     * cursor (or to reset it to normal).  If other shells exist in
     * this application, they will have to be listed here in order
     * for them to have timeout cursors too.
     */
    XChangeWindowAttributes(dpy, XtWindow(shell), CWCursor, &attrs);

    XFlush(dpy);

    if (on) {
        /* we're timing out, put up a WorkingDialog.  If the process
         * is interruptable, allow a "Stop" button.  Otherwise, remove
         * all actions so the user can't stop the processing.
         */
        str = XmStringCreateSimple("Busy.  Please Wait.");
        XtSetArg(args[0], XmNmessageString, str);
        dialog = XmCreateWorkingDialog(shell, "Busy", args, 1);
        XmStringFree(str);
        XtUnmanageChild(
            XmMessageBoxGetChild(dialog, XmDIALOG_OK_BUTTON));
        if (interruptable) {
            str = XmStringCreateSimple("Stop");
            XtVaSetValues(dialog, XmNcancelLabelString, str, NULL);
            XmStringFree(str);
            XtAddCallback(dialog, XmNcancelCallback, stop, NULL);
        } else
            XtUnmanageChild(
                XmMessageBoxGetChild(dialog, XmDIALOG_CANCEL_BUTTON));
        XtUnmanageChild(
            XmMessageBoxGetChild(dialog, XmDIALOG_HELP_BUTTON));
        XtManageChild(dialog);
    } else {
        /* get rid of all button and keyboard events that occured
         * during the time out.  The user shouldn't have done anything
         * during this time, so flush for button and keypress events.
         * KeyRelease events are not discarded because accelerators
         * require the corresponding release event before normal input
         * can continue.
         */
        while (XCheckMaskEvent(dpy,
                ButtonPressMask | ButtonReleaseMask | ButtonMotionMask
                | PointerMotionMask | KeyPressMask, &event)) {
            /* do nothing */;
        }
        XtDestroyWidget(dialog);
    }
}

/* User Pressed the "Stop" button in dialog. */
void
stop(dialog)
Widget dialog;
{
    stopped = True;
}

Boolean
CheckForInterrupt()
{
    extern Widget shell;
    Display *dpy = XtDisplay(shell);
    Window win = XtWindow(dialog);
    XEvent event;

    /* Make sure all our requests get to the server */
    XFlush(dpy);

    /* Let motif process all pending exposure events for us. */
    XmUpdateDisplay(shell);

    /* Check the event loop for events in the dialog ("Stop"?) */
    while (XCheckMaskEvent(dpy,
            ButtonPressMask | ButtonReleaseMask | ButtonMotionMask |
            PointerMotionMask | KeyPressMask | KeyReleaseMask,
            &event)) {
        /* got an "interesting" event. */
        if (event.xany.window == win)
            XtDispatchEvent(&event); /* it's in our dialog.. */
        else /* uninteresting event--throw it away and sound bell */
            XBell(dpy, 50);
    }
    return stopped;
}