patch: centeredmaster

centeredmaster centers the nmaster area on screen, using mfact * monitor
width & height, with the stacked windows distributed to the left and
right.  It can be selected with [Alt]+[u].

With one and two clients in master respectively this results in:

+------------------------------+       +------------------------------+
|+--------++--------++--------+|       |+--------++--------++--------+|
||        ||        ||        ||       ||        ||        ||        ||
||        ||        ||        ||       ||        ||   M1   ||        ||
||        ||        ||        ||       ||        ||        ||        ||
||  S2    ||   M    ||   S1   ||       ||        |+--------+|        ||
||        ||        ||        ||       ||        |+--------+|        ||
||        ||        ||        ||       ||        ||        ||        ||
||        ||        ||        ||       ||        ||   M2   ||        ||
||        ||        ||        ||       ||        ||        ||        ||
|+--------++--------++--------+|       |+--------++--------++--------+|
+------------------------------+       +------------------------------+

This layout can be useful on large screens, where monocle or htile might
be either too large or forcing the user to type in a corner of the
screen.  It allows for instance to center the editor while being able to
keep an eye on background processes (logs, tests, ...).

2 files changed, 58 insertions, 0 deletions

diff --git a/config.def.h b/config.def.h
index aae7682..62319e2 100644
--- a/config.def.h
+++ b/config.def.h
@@ -49,6 +49,7 @@ static const Layout layouts[] = {
 	{ "[]=",      tile },    /* first entry is default */
 	{ "><>",      NULL },    /* no layout function means floating behavior */
 	{ "[M]",      monocle },
+	{ "|M|",      centeredmaster },
 };
 
 /* key definitions */
@@ -96,6 +97,7 @@ static const Key keys[] = {
 	{ MODKEY,                       XK_t,      setlayout,      {.v = &layouts[0]} },
 	{ MODKEY,                       XK_f,      setlayout,      {.v = &layouts[1]} },
 	{ MODKEY,                       XK_m,      setlayout,      {.v = &layouts[2]} },
+	{ MODKEY,                       XK_u,      setlayout,      {.v = &layouts[3]} },
 	{ MODKEY,                       XK_comma,  focusmon,       {.i = -1 } },
 	{ MODKEY,                       XK_period, focusmon,       {.i = +1 } },
 	{ MODKEY|ShiftMask,             XK_comma,  tagmon,         {.i = -1 } },
diff --git a/dwm.c b/dwm.c
index d6391f5..b178c0e 100644
--- a/dwm.c
+++ b/dwm.c
@@ -241,6 +241,7 @@ static int xerrordummy(Display *dpy, XErrorEvent *ee);
 static int xerrorstart(Display *dpy, XErrorEvent *ee);
 static void xinitvisual();
 static void zoom(const Arg *arg);
+static void centeredmaster(Monitor *m);
 
 /* variables */
 static const char broken[] = "broken";
@@ -2280,3 +2281,58 @@ main(int argc, char *argv[])
 	XCloseDisplay(dpy);
 	return EXIT_SUCCESS;
 }
+
+void
+centeredmaster(Monitor *m)
+{
+	unsigned int i, n, h, mw, mx, my, oty, ety, tw;
+	Client *c;
+
+	/* count number of clients in the selected monitor */
+	for (n = 0, c = nexttiled(m->clients); c; c = nexttiled(c->next), n++);
+	if (n == 0)
+		return;
+
+	/* initialize areas */
+	mw = m->ww;
+	mx = 0;
+	my = 0;
+	tw = mw;
+
+	if (n > m->nmaster) {
+		/* go mfact box in the center if more than nmaster clients */
+		mw = m->nmaster ? m->ww * m->mfact : 0;
+		tw = m->ww - mw;
+
+		if (n - m->nmaster > 1) {
+			/* only one client */
+			mx = (m->ww - mw) / 2;
+			tw = (m->ww - mw) / 2;
+		}
+	}
+
+	oty = 0;
+	ety = 0;
+	for (i = 0, c = nexttiled(m->clients); c; c = nexttiled(c->next), i++)
+	if (i < m->nmaster) {
+		/* nmaster clients are stacked vertically, in the center
+		 * of the screen */
+		h = (m->wh - my) / (MIN(n, m->nmaster) - i);
+		resize(c, m->wx + mx, m->wy + my, mw - (2*c->bw),
+		       h - (2*c->bw), 0);
+		my += HEIGHT(c);
+	} else {
+		/* stack clients are stacked vertically */
+		if ((i - m->nmaster) % 2 ) {
+			h = (m->wh - ety) / ( (1 + n - i) / 2);
+			resize(c, m->wx, m->wy + ety, tw - (2*c->bw),
+			       h - (2*c->bw), 0);
+			ety += HEIGHT(c);
+		} else {
+			h = (m->wh - oty) / ((1 + n - i) / 2);
+			resize(c, m->wx + mx + mw, m->wy + oty,
+			       tw - (2*c->bw), h - (2*c->bw), 0);
+			oty += HEIGHT(c);
+		}
+	}
+}