From b1ca46930756b59c1ebba0b8c7871b85ff84f62f Mon Sep 17 00:00:00 2001
From: Nikita Ivanov <nikita.vyach.ivanov@gmail.com>
Date: Sat, 8 Feb 2025 16:10:25 +0100
Subject: [PATCH] Add centeredmaster layout

This is a port of centeredmaster patch for dwm:
    https://dwm.suckless.org/patches/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]+[c].

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

+------------------------------+       +------------------------------+
|+--------++--------++--------+|       |+--------++--------++--------+|
||        ||        ||        ||       ||        ||        ||        ||
||        ||        ||        ||       ||        ||   M1   ||        ||
||        ||        ||        ||       ||        ||        ||        ||
||  S2    ||   M    ||   S1   ||       ||        |+--------+|        ||
||        ||        ||        ||       ||        |+--------+|        ||
||        ||        ||        ||       ||        ||        ||        ||
||        ||        ||        ||       ||        ||   M2   ||        ||
||        ||        ||        ||       ||        ||        ||        ||
|+--------++--------++--------+|       |+--------++--------++--------+|
+------------------------------+       +------------------------------+
---
 config.def.h |  2 ++
 dwl.c        | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/config.def.h b/config.def.h
index 22d2171..9a3b0c5 100644
--- a/config.def.h
+++ b/config.def.h
@@ -34,6 +34,7 @@ static const Layout layouts[] = {
 	{ "[]=",      tile },
 	{ "><>",      NULL },    /* no layout function means floating behavior */
 	{ "[M]",      monocle },
+	{ "|M|",      centeredmaster },
 };
 
 /* monitors */
@@ -139,6 +140,7 @@ static const Key keys[] = {
 	{ MODKEY,                    XKB_KEY_t,          setlayout,      {.v = &layouts[0]} },
 	{ MODKEY,                    XKB_KEY_f,          setlayout,      {.v = &layouts[1]} },
 	{ MODKEY,                    XKB_KEY_m,          setlayout,      {.v = &layouts[2]} },
+	{ MODKEY,                    XKB_KEY_c,          setlayout,      {.v = &layouts[3]} },
 	{ MODKEY,                    XKB_KEY_space,      setlayout,      {0} },
 	{ MODKEY|WLR_MODIFIER_SHIFT, XKB_KEY_space,      togglefloating, {0} },
 	{ MODKEY,                    XKB_KEY_e,         togglefullscreen, {0} },
diff --git a/dwl.c b/dwl.c
index def2562..c2456dd 100644
--- a/dwl.c
+++ b/dwl.c
@@ -251,6 +251,7 @@ static void arrangelayer(Monitor *m, struct wl_list *list,
 static void arrangelayers(Monitor *m);
 static void axisnotify(struct wl_listener *listener, void *data);
 static void buttonpress(struct wl_listener *listener, void *data);
+static void centeredmaster(Monitor *m);
 static void chvt(const Arg *arg);
 static void checkidleinhibitor(struct wlr_surface *exclude);
 static void cleanup(void);
@@ -649,6 +650,68 @@ buttonpress(struct wl_listener *listener, void *data)
 			event->time_msec, event->button, event->state);
 }
 
+void
+centeredmaster(Monitor *m)
+{
+	int i, n, h, mw, mx, my, oty, ety, tw;
+	Client *c;
+
+	n = 0;
+	wl_list_for_each(c, &clients, link)
+		if (VISIBLEON(c, m) && !c->isfloating && !c->isfullscreen)
+			n++;
+	if (n == 0)
+		return;
+
+	/* initialize areas */
+	mw = m->w.width;
+	mx = 0;
+	my = 0;
+	tw = mw;
+
+	if (n > m->nmaster) {
+		/* go mfact box in the center if more than nmaster clients */
+		mw = m->nmaster ? (int)roundf(m->w.width * m->mfact) : 0;
+		tw = m->w.width - mw;
+
+		if (n - m->nmaster > 1) {
+			/* only one client */
+			mx = (m->w.width - mw) / 2;
+			tw = (m->w.width - mw) / 2;
+		}
+	}
+
+	i = 0;
+	oty = 0;
+	ety = 0;
+	wl_list_for_each(c, &clients, link) {
+		if (!VISIBLEON(c, m) || c->isfloating || c->isfullscreen)
+			continue;
+		if (i < m->nmaster) {
+			/* nmaster clients are stacked vertically, in the center
+			 * of the screen */
+			h = (m->w.height - my) / (MIN(n, m->nmaster) - i);
+			resize(c, (struct wlr_box){.x = m->w.x + mx, .y = m->w.y + my, .width = mw,
+				   .height = h}, 0);
+			my += c->geom.height;
+		} else {
+			/* stack clients are stacked vertically */
+			if ((i - m->nmaster) % 2) {
+				h = (m->w.height - ety) / ( (1 + n - i) / 2);
+				resize(c, (struct wlr_box){.x = m->w.x, .y = m->w.y + ety, .width = tw,
+					   .height = h}, 0);
+				ety += c->geom.height;
+			} else {
+				h = (m->w.height - oty) / ((1 + n - i) / 2);
+				resize(c, (struct wlr_box){.x = m->w.x + mx + mw, .y = m->w.y + oty, .width = tw,
+					.height = h}, 0);
+				oty += c->geom.height;
+			}
+		}
+		i++;
+	}
+}
+
 void
 chvt(const Arg *arg)
 {
-- 
2.48.1