Monitor rules patch

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.

config.def.h

@@ -101,6 +101,12 @@ static const BarRule barrules[] = {
 	{ 'A',      0,     BAR_ALIGN_RIGHT,  width_status2d,        draw_status2d,        click_statuscmd,    "status2d" },
 	{ 'A',      0,     BAR_ALIGN_RIGHT,  width_systray,         draw_systray,         click_systray,      "systray" },
 	{ -1,       0,     BAR_ALIGN_NONE,   width_wintitle,        draw_wintitle,        click_wintitle,     "wintitle" },
+}
+
+static const MonitorRule monrules[] = {
+	/* monitor layout  mfact  nmaster  showbar  tagset */
+	{  -1,     0,      -1,    -1,      -1,      0       }, // default
+};
 
 /* layout(s) */
 static const float mfact     = 0.55; /* factor of master area size [0.05..0.95] */

config.h

@@ -88,8 +88,8 @@ static const Rule rules[] = {
 	RULE(.type = WTYPE "SPLASH",  .isfloating = 1)
 	RULE(.class = "feh",             .tags = 0)
 	// RULE(.class = "kitty",           .isterminal = 1)
-	RULE(.title = "Discord Updater", .tags = 1 << 4, .isfloating = 1, .matchonce = 1, .floatpos = "50% 50%", .monitor = 1)
-	RULE(.class = "discord",         .tags = 1 << 4, .monitor = 1)
+	RULE(.title = "Discord Updater", .tags = 1 << 4, .isfloating = 1, .matchonce = 1, .floatpos = "50% 50%")
+	RULE(.class = "discord",         .tags = 1 << 4)
 	RULE(.class = "lutris",          .isfloating = 1)
 };
 
@@ -123,6 +123,13 @@ static const BarRule barrules[] = {
 	{ -1,       0,     BAR_ALIGN_NONE,   width_wintitle,        draw_wintitle,        click_wintitle,     "wintitle" },
 };
 
+static const MonitorRule monrules[] = {
+	/* monitor layout  mfact  nmaster  showbar  tagset */
+	{  1,      0,      -1,    -1,      -1,      1 << 5  },
+	{  2,      0,      -1,    -1,      -1,      1 << 4  },
+	{  -1,     0,      -1,    -1,      -1,      0       }, // default
+};
+
 static const Layout layouts[] = {
 	/* symbol     arrange function */
 	{ "[]=",      tile },    /* first entry is default */

dwm.c

@@ -1,4 +1,4 @@
-/* See LICENSE file for copyright and license details.
+/* See LICENSE file for cpyright and license details.
  *
  * dynamic window manager is designed like any other X client as well. It is
  * driven through handling X events. In contrast to other X clients, a window
@@ -242,6 +242,15 @@ struct Clientlist {
 	Client *stack;
 };
 
+typedef struct {
+	int monitor;
+	int layout;
+	float mfact;
+	int nmaster;
+	int showbar;
+	unsigned int tagset;
+} MonitorRule;
+
 /* function declarations */
 static void applyrules(Client *c);
 static int applysizehints(Client *c, int *x, int *y, int *w, int *h, int interact);
@@ -898,6 +907,8 @@ createmon(void)
 
 	const BarRule *br;
 	Bar *bar;
+	unsigned int j;
+	const MonitorRule *mr;
 
 	/* bail out if the number of monitors exceeds the number of tags */
 	for (i=1, tm=mons; tm; i++, tm=tm->next);
@@ -926,9 +937,6 @@ createmon(void)
 	m->showbar = showbar;
 
 	for (mi = 0, mon = mons; mon; mon = mon->next, mi++); // monitor index
-	m->lt[0] = &layouts[0];
-	m->lt[1] = &layouts[1 % LENGTH(layouts)];
-	strncpy(m->ltsymbol, layouts[0].symbol, sizeof m->ltsymbol);
 
 	/* Derive the number of bars for this monitor based on bar rules */
 	for (n = -1, i = 0; i < LENGTH(barrules); i++) {
@@ -947,6 +955,24 @@ createmon(void)
 		istopbar = !istopbar;
 	}
 
+	for (j = 0; j < LENGTH(monrules); j++) {
+		mr = &monrules[j];
+		if ((mr->monitor == -1 || mr->monitor == mi)) {
+			m->lt[0] = &layouts[mr->layout];
+			m->lt[1] = &layouts[1 % LENGTH(layouts)];
+			strncpy(m->ltsymbol, layouts[mr->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->tagset)
+				m->tagset[m->seltags] = mr->tagset;
+			break;
+		}
+	}
 	return m;
 }