From 6d63b19999c52c4a83bf4b7770cb119d9eb4dd59 Mon Sep 17 00:00:00 2001
From: bakkeby <bakkeby@gmail.com>
Date: Wed, 29 Jul 2020 11:19:33 +0200
Subject: [PATCH 2/2] Monitor rules patch on top of pertag

This patch allows the user to define layout, mfact, nmaster, showbar,
and topbar settings on a per monitor basis. An example use case could
be to have a layout with a horizontal split for a secondary vertical
monitor.

https://github.com/bakkeby/patches/wiki/monitorrules
---
 config.def.h |  6 +++++
 dwm.c        | 70 +++++++++++++++++++++++++++++++++++++++-------------
 2 files changed, 59 insertions(+), 17 deletions(-)

diff --git a/config.def.h b/config.def.h
index 1c0b587..36bfa8c 100644
--- a/config.def.h
+++ b/config.def.h
@@ -43,6 +43,12 @@ static const Layout layouts[] = {
 	{ "[M]",      monocle },
 };
 
+static const MonitorRule monrules[] = {
+	/* monitor  tag  layout  mfact  nmaster  showbar  topbar */
+	{  1,       -1,  2,      -1,    -1,      -1,      -1     }, // use a different layout for the second monitor
+	{  -1,      -1,  0,      -1,    -1,      -1,      -1     }, // default
+};
+
 /* key definitions */
 #define MODKEY Mod1Mask
 #define TAGKEYS(KEY,TAG) \
diff --git a/dwm.c b/dwm.c
index 55f8f92..357c3d7 100644
--- a/dwm.c
+++ b/dwm.c
@@ -143,6 +143,16 @@ typedef struct {
 	int monitor;
 } Rule;
 
+typedef struct {
+	int monitor;
+	int tag;
+	int layout;
+	float mfact;
+	int nmaster;
+	int showbar;
+	int topbar;
+} MonitorRule;
+
 /* function declarations */
 static void applyrules(Client *c);
 static int applysizehints(Client *c, int *x, int *y, int *w, int *h, int interact);
@@ -642,38 +652,64 @@ configurerequest(XEvent *e)
 Monitor *
 createmon(void)
 {
-	Monitor *m;
-	int i;
-
+	Monitor *m, *mi;
+	int i, mc, j, layout;
+	const MonitorRule *mr;
 	m = ecalloc(1, sizeof(Monitor));
 	m->tagset[0] = m->tagset[1] = 1;
 	m->mfact = mfact;
 	m->nmaster = nmaster;
 	m->showbar = showbar;
 	m->topbar = topbar;
-	m->lt[0] = &layouts[0];
-	m->lt[1] = &layouts[1 % LENGTH(layouts)];
-	strncpy(m->ltsymbol, layouts[0].symbol, sizeof m->ltsymbol);
+
+	for (mc = 0, mi = mons; mi; mi = mi->next, mc++);
+	for (j = 0; j < LENGTH(monrules); j++) {
+		mr = &monrules[j];
+		if ((mr->monitor == -1 || mr->monitor == mc)
+				&& (mr->tag <= 0 || (m->tagset[0] & (1 << (mr->tag - 1))))
+		) {
+			layout = MAX(mr->layout, 0);
+			layout = MIN(layout, LENGTH(layouts) - 1);
+			m->lt[0] = &layouts[layout];
+			m->lt[1] = &layouts[1 % LENGTH(layouts)];
+			strncpy(m->ltsymbol, layouts[layout].symbol, sizeof m->ltsymbol);
+
+			if (mr->mfact > -1)
+				m->mfact = mr->mfact;
+			if (mr->nmaster > -1)
+				m->nmaster = mr->nmaster;
+			if (mr->showbar > -1)
+				m->showbar = mr->showbar;
+			if (mr->topbar > -1)
+				m->topbar = mr->topbar;
+			break;
+		}
+	}
+
 	if (!(m->pertag = (Pertag *)calloc(1, sizeof(Pertag))))
 		die("fatal: could not malloc() %u bytes\n", sizeof(Pertag));
 	m->pertag->curtag = m->pertag->prevtag = 1;
-	for (i = 0; i <= LENGTH(tags); i++) {
-		/* init nmaster */
-		m->pertag->nmasters[i] = m->nmaster;
-
-		/* init mfacts */
-		m->pertag->mfacts[i] = m->mfact;
 
+	for (i = 0; i <= LENGTH(tags); i++) {
 		/* init layouts */
-		m->pertag->ltidxs[i][0] = m->lt[0];
-		m->pertag->ltidxs[i][1] = m->lt[1];
 		m->pertag->sellts[i] = m->sellt;
 
-		/* init showbar */
-		m->pertag->showbars[i] = m->showbar;
-
 		/* swap focus and zoomswap*/
 		m->pertag->prevzooms[i] = NULL;
+
+		for (j = 0; j < LENGTH(monrules); j++) {
+			mr = &monrules[j];
+			if ((mr->monitor == -1 || mr->monitor == mc) && (mr->tag == -1 || mr->tag == i)) {
+				layout = MAX(mr->layout, 0);
+				layout = MIN(layout, LENGTH(layouts) - 1);
+				m->pertag->ltidxs[i][0] = &layouts[layout];
+				m->pertag->ltidxs[i][1] = m->lt[0];
+				m->pertag->nmasters[i] = (mr->nmaster > -1 ? mr->nmaster : m->nmaster);
+				m->pertag->mfacts[i] = (mr->mfact > -1 ? mr->mfact : m->mfact);
+				m->pertag->showbars[i] = (mr->showbar > -1 ? mr->showbar : m->showbar);
+				break;
+			}
+		}
 	}
 	return m;
 }
-- 
2.19.1