dwm-flexipatch/patch/setborderpx.c

void
setborderpx(const Arg *arg)
{
	Client *c;
	int prev_borderpx = selmon->borderpx;

	if (arg->i == 0)
		mons->borderpx = borderpx;
	else if (mons->borderpx + arg->i < 0)
		mons->borderpx = 0;
	else
		mons->borderpx += arg->i;

	for (c = mons->clients; c; c = c->next)
	{
		if (c->bw + arg->i < 0)
			c->bw = mons->borderpx = 0;
		else
			c->bw = mons->borderpx;
		if (c->isfloating || !selmon->lt[selmon->sellt]->arrange)
		{
			if (arg->i != 0 && prev_borderpx + arg->i >= 0)
				resize(c, c->x, c->y, c->w-(arg->i*2), c->h-(arg->i*2), 0);
			else if (arg->i == 0 && prev_borderpx > borderpx)
				resize(c, c->x + prev_borderpx - borderpx, c->y + prev_borderpx - borderpx, c->w, c->h, 0);
			else if (arg->i == 0 && prev_borderpx < borderpx)
				resize(c, c->x, c->y, c->w-2*(borderpx - prev_borderpx), c->h-2*(borderpx - prev_borderpx), 0);
		}
	}

	arrange(selmon);
}