9clock.c

/*
  * 9clock.c: a basic graphical clock for plan 9
  * sean caron (scaron@umich.edu)
*/

/*
  * The paradigm here is that we must always include u.h
  * first and libc.h second, and anything else after that.
*/

#include <u.h>
#include <libc.h>
#include <draw.h>
#include <cursor.h>
#include <event.h>

int main(void);
void eresized(int new);

int main(void) {
    Point center, minend, hrend, o_minend, o_hrend;
    Tm *thetime;
    int xdim, ydim, fd;
    double mintheta, hrtheta;
    char *buttons[] = { "quit", 0 };
    Menu menu = { buttons };
    Mouse m;
    Event e;
    ulong timer, evtype;

    initdraw(nil, nil, "9clock");

    /*
     * initialize event handler for mouse events only. we
     * must call this subsequent to initdraw().
    */
    einit(Emouse);

    /* we need to call this resize handler at least once */
    eresized(0);

    /*
     * we need to set up this timer event because when you use
     * the event() system call, it basically blocks until some sort
     * of event occurs. we use the timer event in lieu of a real
     * event occurring or else the clock would not update until
     * the user moved the mouse or clicked a button.
    */
    timer = etimer(0,10);

    /*
     * initdraw() sets up some global variables,
     *
     * Display *display
     * Image *screen
     * Screen *_screen
     * Font *font
     *
     * ZP is a constant point (0,0).
    */

    /* resize the current window. */
    fd = open("/dev/wctl", OWRITE);
    fprint(fd, "resize -dx 200 -dy 200");
    close(fd);

    getwindow(display, Refnone);

    /* initialize some variables. */
    xdim = (screen->r.max.x - screen->r.min.x) / 2;
    ydim = (screen->r.max.y - screen->r.min.y) / 2;

    center.x = screen->r.min.x + xdim;
    center.y = screen->r.min.y + ydim;

    /* main program loop */
    while (1) {
        evtype = event(&e);

        /* look for mouse events */
        if (evtype == Emouse) {
            m = e.mouse;

            /* if left mouse button is clicked, show the menu */
            if (m.buttons == 4) {
                /* quit */
                if (emenuhit(3, &m, &menu) == 0) {
                    closedisplay(display);
		    exits(0);
                }
            }
        }

        /* use the faux timer event to update the clock if there is no real input */
        else if (event(&e) == timer) {
            /* draw outline of clock face. */
            ellipse(screen, center, xdim, ydim, 2, display->black, center);

            thetime = localtime(time(nil));

            /* correct 24 hour system time to 12 hour clock. */
            if (thetime->hour > 12) {
                thetime->hour = thetime->hour - 12;
            }

            /*
             * 6 degrees = 0.104718 rads per minute on the clock face.
             * 30 degrees = 0.523590 rads per hour on the clock face.
             *
             * we subtract the value from PI/2 to correct between standard
             * form and clock form.
            */

            mintheta = (PI/2.0) - (0.104718 * (double)thetime->min);
            hrtheta = (PI/2.0) - (0.523590 * (double)thetime->hour);

            /*
             * calculate the endpoints for the minute and hour hands.
             * we resize the window to be square so xdim and ydim are actually the same.
             * we scale down the hour hand to make it shorter than the minute hand.
            */

            minend.x = center.x + (double)xdim*cos(mintheta);
            minend.y = center.y - (double)ydim*sin(mintheta);

            hrend.x = center.x + (double)xdim*cos(hrtheta);
            hrend.y = center.y - (double)ydim*sin(hrtheta);

            /*
             * if the time has changed since the last time we looped, get rid of the stale minute or
             * hour hands.
            */
            if ((o_minend.x != minend.x) || (o_minend.y != minend.y)) {
                line(screen, center, o_minend, Endsquare, Endarrow, 1, display->white, center);
            }

            if ((o_hrend.x != hrend.x) || (o_hrend.y != hrend.y)) {
                line(screen, center, o_hrend, Endsquare, Endarrow, 2, display->white, center);
            }

            /* draw the current minute and hour hands. */
            line(screen, center, minend, Endsquare, Endarrow, 1, display->black, center);
            line(screen, center, hrend, Endsquare, Endarrow, 2, display->black, center);

            /* save the minute and hour hand coordinates for comparison the next time around. */
            o_minend = minend;
            o_hrend = hrend;

            /* let some other processes get a word in edgewise. */
            sleep(1);

            /*
             * the draw (2) manpage suggests that this is not required, but the graphics will not
             * show up unless we use it.
            */
            flushimage(display,1);
        }
    }
}

/*
  * by convention we must declare an eresized() function to
  * handle the window resizing event.
*/

void eresized(int new) {
    /* just refresh the window for now. */
    getwindow(display, Refnone);
}