dwm/patch/placemouse.c

void
moveorplace(const Arg *arg) {
	if ((!selmon->lt[selmon->sellt]->arrange || (selmon->sel && selmon->sel->isfloating)))
		movemouse(arg);
	else
		placemouse(arg);
}

void
placemouse(const Arg *arg)
{
	int x, y, px, py, ocx, ocy, nx = -9999, ny = -9999, freemove = 0;
	Client *c, *r = NULL, *at, *prevr;
	Monitor *m;
	XEvent ev;
	XWindowAttributes wa;
	Time lasttime = 0;
	int attachmode, prevattachmode;
	attachmode = prevattachmode = -1;

	if (!(c = selmon->sel) || !c->mon->lt[c->mon->sellt]->arrange) /* no support for placemouse when floating layout is used */
		return;
	if (c->isfullscreen) /* no support placing fullscreen windows by mouse */
		return;
	restack(selmon);
	prevr = c;
	if (XGrabPointer(dpy, root, False, MOUSEMASK, GrabModeAsync, GrabModeAsync,
		None, cursor[CurMove]->cursor, CurrentTime) != GrabSuccess)
		return;

	c->isfloating = 0;
	c->beingmoved = 1;

	XGetWindowAttributes(dpy, c->win, &wa);
	ocx = wa.x;
	ocy = wa.y;

	if (arg->i == 2) // warp cursor to client center
		XWarpPointer(dpy, None, c->win, 0, 0, 0, 0, WIDTH(c) / 2, HEIGHT(c) / 2);

	if (!getrootptr(&x, &y))
		return;

	do {
		XMaskEvent(dpy, MOUSEMASK|ExposureMask|SubstructureRedirectMask, &ev);
		switch (ev.type) {
		case ConfigureRequest:
		case Expose:
		case MapRequest:
			handler[ev.type](&ev);
			break;
		case MotionNotify:
			if ((ev.xmotion.time - lasttime) <= (1000 / 60))
				continue;
			lasttime = ev.xmotion.time;

			nx = ocx + (ev.xmotion.x - x);
			ny = ocy + (ev.xmotion.y - y);

			if (!freemove && (abs(nx - ocx) > snap || abs(ny - ocy) > snap))
				freemove = 1;

			if (freemove)
				XMoveWindow(dpy, c->win, nx, ny);

			if ((m = recttomon(ev.xmotion.x, ev.xmotion.y, 1, 1)) && m != selmon)
				selmon = m;

			if (arg->i == 1) { // tiled position is relative to the client window center point
				px = nx + wa.width / 2;
				py = ny + wa.height / 2;
			} else { // tiled position is relative to the mouse cursor
				px = ev.xmotion.x;
				py = ev.xmotion.y;
			}

			r = recttoclient(px, py, 1, 1);

			if (!r || r == c)
				break;

			if ((((float)(r->y + r->h - py) / r->h) > ((float)(r->x + r->w - px) / r->w)
			    	&& (abs(r->y - py) < r->h / 2)) || (abs(r->x - px) < r->w / 2))
				attachmode = 1; // above
			else
				attachmode = 0; // below

			if ((r && r != prevr) || (attachmode != prevattachmode)) {
				detachstack(c);
				detach(c);
				if (c->mon != r->mon) {
					arrangemon(c->mon);
					c->tags = r->mon->tagset[r->mon->seltags];
				}

				c->mon = r->mon;
				r->mon->sel = r;

				if (attachmode) {
					if (r == r->mon->clients)
						attach(c);
					else {
						for (at = r->mon->clients; at->next != r; at = at->next);
						c->next = at->next;
						at->next = c;
					}
				} else {
					c->next = r->next;
					r->next = c;
				}

				attachstack(c);
				arrangemon(r->mon);
				prevr = r;
				prevattachmode = attachmode;
			}
			break;
		}
	} while (ev.type != ButtonRelease);
	XUngrabPointer(dpy, CurrentTime);

	if ((m = recttomon(ev.xmotion.x, ev.xmotion.y, 1, 1)) && m != c->mon) {
		detach(c);
		detachstack(c);
		arrangemon(c->mon);
		c->mon = m;
		c->tags = m->tagset[m->seltags];
		attach(c);
		attachstack(c);
		selmon = m;
	}

	focus(c);
	c->beingmoved = 0;

	if (nx != -9999)
		resize(c, nx, ny, c->w, c->h, 0);
	arrangemon(c->mon);
}

Client *
recttoclient(int x, int y, int w, int h)
{
	Client *c, *r = NULL;
	int a, area = 0;

	for (c = nexttiled(selmon->clients); c; c = nexttiled(c->next)) {
		if ((a = INTERSECTC(x, y, w, h, c)) > area) {
			area = a;
			r = c;
		}
	}
	return r;
}