Add gaps

Many users new to dwm find themselves caught out by being kicked out to the login manager (dwm crashing) when they open 50+ clients for demonstration purposes. The number of clients reported varies depending on the resolution of the monitor.

The cause of this is due to how the default tile layout calculates the height of the next client based on the position of the previous client. Because clients have a minimum size the (ty) position can exceed that of the window height, resulting in (m->wh - ty) becoming negative. The negative height stored as an unsigned int results in a very large height ultimately resulting in dwm crashing.

This patch adds safeguards to prevent the ty and my positions from exceeding that of the window height.

config.def.h

@@ -3,6 +3,11 @@
 /* appearance */
 static const unsigned int borderpx  = 1;        /* border pixel of windows */
 static const unsigned int snap      = 32;       /* snap pixel */
+static const unsigned int gappih    = 10;       /* horiz inner gap between windows */
+static const unsigned int gappiv    = 10;       /* vert inner gap between windows */
+static const unsigned int gappoh    = 10;       /* horiz outer gap between windows and screen edge */
+static const unsigned int gappov    = 10;       /* vert outer gap between windows and screen edge */
+static const int smartgaps          = 0;        /* 1 means no outer gap when there is only one window */
 static const int showbar            = 1;        /* 0 means no bar */
 static const int topbar             = 1;        /* 0 means bottom bar */
 static const char *fonts[]          = { "monospace:size=10" };
@@ -70,6 +75,22 @@ static Key keys[] = {
 	{ MODKEY,                       XK_d,      incnmaster,     {.i = -1 } },
 	{ MODKEY,                       XK_h,      setmfact,       {.f = -0.05} },
 	{ MODKEY,                       XK_l,      setmfact,       {.f = +0.05} },
+	{ MODKEY|Mod4Mask,              XK_h,      incrgaps,       {.i = +1 } },
+	{ MODKEY|Mod4Mask,              XK_l,      incrgaps,       {.i = -1 } },
+	{ MODKEY|Mod4Mask|ShiftMask,    XK_h,      incrogaps,      {.i = +1 } },
+	{ MODKEY|Mod4Mask|ShiftMask,    XK_l,      incrogaps,      {.i = -1 } },
+	{ MODKEY|Mod4Mask|ControlMask,  XK_h,      incrigaps,      {.i = +1 } },
+	{ MODKEY|Mod4Mask|ControlMask,  XK_l,      incrigaps,      {.i = -1 } },
+	{ MODKEY|Mod4Mask,              XK_0,      togglegaps,     {0} },
+	{ MODKEY|Mod4Mask|ShiftMask,    XK_0,      defaultgaps,    {0} },
+	{ MODKEY,                       XK_y,      incrihgaps,     {.i = +1 } },
+	{ MODKEY,                       XK_o,      incrihgaps,     {.i = -1 } },
+	{ MODKEY|ControlMask,           XK_y,      incrivgaps,     {.i = +1 } },
+	{ MODKEY|ControlMask,           XK_o,      incrivgaps,     {.i = -1 } },
+	{ MODKEY|Mod4Mask,              XK_y,      incrohgaps,     {.i = +1 } },
+	{ MODKEY|Mod4Mask,              XK_o,      incrohgaps,     {.i = -1 } },
+	{ MODKEY|ShiftMask,             XK_y,      incrovgaps,     {.i = +1 } },
+	{ MODKEY|ShiftMask,             XK_o,      incrovgaps,     {.i = -1 } },
 	{ MODKEY,                       XK_Return, zoom,           {0} },
 	{ MODKEY,                       XK_Tab,    view,           {0} },
 	{ MODKEY|ShiftMask,             XK_c,      killclient,     {0} },

config.mk

@@ -25,7 +25,7 @@ INCS = -I${X11INC} -I${FREETYPEINC}
 LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS}
 
 # flags
-CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_C_SOURCE=2 -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
+CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_C_SOURCE=200809L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
 #CFLAGS   = -g -std=c99 -pedantic -Wall -O0 ${INCS} ${CPPFLAGS}
 CFLAGS   = -std=c99 -pedantic -Wall -Wno-deprecated-declarations -Os ${INCS} ${CPPFLAGS}
 LDFLAGS  = ${LIBS}

dwm.c

@@ -119,6 +119,10 @@ struct Monitor {
 	int by;               /* bar geometry */
 	int mx, my, mw, mh;   /* screen size */
 	int wx, wy, ww, wh;   /* window area  */
+	int gappih;           /* horizontal gap between windows */
+	int gappiv;           /* vertical gap between windows */
+	int gappoh;           /* horizontal outer gaps */
+	int gappov;           /* vertical outer gaps */
 	unsigned int seltags;
 	unsigned int sellt;
 	unsigned int tagset[2];
@@ -169,6 +173,7 @@ static void focus(Client *c);
 static void focusin(XEvent *e);
 static void focusmon(const Arg *arg);
 static void focusstack(const Arg *arg);
+static Atom getatomprop(Client *c, Atom prop);
 static int getrootptr(int *x, int *y);
 static long getstate(Window w);
 static int gettextprop(Window w, Atom atom, char *text, unsigned int size);
@@ -199,6 +204,16 @@ static void sendmon(Client *c, Monitor *m);
 static void setclientstate(Client *c, long state);
 static void setfocus(Client *c);
 static void setfullscreen(Client *c, int fullscreen);
+static void setgaps(int oh, int ov, int ih, int iv);
+static void incrgaps(const Arg *arg);
+static void incrigaps(const Arg *arg);
+static void incrogaps(const Arg *arg);
+static void incrohgaps(const Arg *arg);
+static void incrovgaps(const Arg *arg);
+static void incrihgaps(const Arg *arg);
+static void incrivgaps(const Arg *arg);
+static void togglegaps(const Arg *arg);
+static void defaultgaps(const Arg *arg);
 static void setlayout(const Arg *arg);
 static void setmfact(const Arg *arg);
 static void setup(void);
@@ -240,6 +255,7 @@ static char stext[256];
 static int screen;
 static int sw, sh;           /* X display screen geometry width, height */
 static int bh, blw = 0;      /* bar geometry */
+static int enablegaps = 1;   /* enables gaps, used by togglegaps */
 static int lrpad;            /* sum of left and right padding for text */
 static int (*xerrorxlib)(Display *, XErrorEvent *);
 static unsigned int numlockmask = 0;
@@ -638,6 +654,10 @@ createmon(void)
 	m->nmaster = nmaster;
 	m->showbar = showbar;
 	m->topbar = topbar;
+	m->gappih = gappih;
+	m->gappiv = gappiv;
+	m->gappoh = gappoh;
+	m->gappov = gappov;
 	m->lt[0] = &layouts[0];
 	m->lt[1] = &layouts[1 % LENGTH(layouts)];
 	strncpy(m->ltsymbol, layouts[0].symbol, sizeof m->ltsymbol);
@@ -695,7 +715,7 @@ dirtomon(int dir)
 void
 drawbar(Monitor *m)
 {
-	int x, w, sw = 0;
+	int x, w, tw = 0;
 	int boxs = drw->fonts->h / 9;
 	int boxw = drw->fonts->h / 6 + 2;
 	unsigned int i, occ = 0, urg = 0;
@@ -704,8 +724,8 @@ drawbar(Monitor *m)
 	/* draw status first so it can be overdrawn by tags later */
 	if (m == selmon) { /* status is only drawn on selected monitor */
 		drw_setscheme(drw, scheme[SchemeNorm]);
-		sw = TEXTW(stext) - lrpad + 2; /* 2px right padding */
-		drw_text(drw, m->ww - sw, 0, sw, bh, 0, stext, 0);
+		tw = TEXTW(stext) - lrpad + 2; /* 2px right padding */
+		drw_text(drw, m->ww - tw, 0, tw, bh, 0, stext, 0);
 	}
 
 	for (c = m->clients; c; c = c->next) {
@@ -728,7 +748,7 @@ drawbar(Monitor *m)
 	drw_setscheme(drw, scheme[SchemeNorm]);
 	x = drw_text(drw, x, 0, w, bh, lrpad / 2, m->ltsymbol, 0);
 
-	if ((w = m->ww - sw - x) > bh) {
+	if ((w = m->ww - tw - x) > bh) {
 		if (m->sel) {
 			drw_setscheme(drw, scheme[m == selmon ? SchemeSel : SchemeNorm]);
 			drw_text(drw, x, 0, w, bh, lrpad / 2, m->sel->name, 0);
@@ -1497,6 +1517,111 @@ setfullscreen(Client *c, int fullscreen)
 	}
 }
 
+void
+setgaps(int oh, int ov, int ih, int iv)
+{
+	if (oh < 0) oh = 0;
+	if (ov < 0) ov = 0;
+	if (ih < 0) ih = 0;
+	if (iv < 0) iv = 0;
+
+	selmon->gappoh = oh;
+	selmon->gappov = ov;
+	selmon->gappih = ih;
+	selmon->gappiv = iv;
+	arrange(selmon);
+}
+
+void
+togglegaps(const Arg *arg)
+{
+	enablegaps = !enablegaps;
+	arrange(selmon);
+}
+
+void
+defaultgaps(const Arg *arg)
+{
+	setgaps(gappoh, gappov, gappih, gappiv);
+}
+
+void
+incrgaps(const Arg *arg)
+{
+	setgaps(
+		selmon->gappoh + arg->i,
+		selmon->gappov + arg->i,
+		selmon->gappih + arg->i,
+		selmon->gappiv + arg->i
+	);
+}
+
+void
+incrigaps(const Arg *arg)
+{
+	setgaps(
+		selmon->gappoh,
+		selmon->gappov,
+		selmon->gappih + arg->i,
+		selmon->gappiv + arg->i
+	);
+}
+
+void
+incrogaps(const Arg *arg)
+{
+	setgaps(
+		selmon->gappoh + arg->i,
+		selmon->gappov + arg->i,
+		selmon->gappih,
+		selmon->gappiv
+	);
+}
+
+void
+incrohgaps(const Arg *arg)
+{
+	setgaps(
+		selmon->gappoh + arg->i,
+		selmon->gappov,
+		selmon->gappih,
+		selmon->gappiv
+	);
+}
+
+void
+incrovgaps(const Arg *arg)
+{
+	setgaps(
+		selmon->gappoh,
+		selmon->gappov + arg->i,
+		selmon->gappih,
+		selmon->gappiv
+	);
+}
+
+void
+incrihgaps(const Arg *arg)
+{
+	setgaps(
+		selmon->gappoh,
+		selmon->gappov,
+		selmon->gappih + arg->i,
+		selmon->gappiv
+	);
+}
+
+void
+incrivgaps(const Arg *arg)
+{
+	setgaps(
+		selmon->gappoh,
+		selmon->gappov,
+		selmon->gappih,
+		selmon->gappiv + arg->i
+	);
+}
+
 void
 setlayout(const Arg *arg)
 {
@@ -1520,7 +1645,7 @@ setmfact(const Arg *arg)
 	if (!arg || !selmon->lt[selmon->sellt]->arrange)
 		return;
 	f = arg->f < 1.0 ? arg->f + selmon->mfact : arg->f - 1.0;
-	if (f < 0.1 || f > 0.9)
+	if (f < 0.05 || f > 0.95)
 		return;
 	selmon->mfact = f;
 	arrange(selmon);
@@ -1673,26 +1798,32 @@ tagmon(const Arg *arg)
 void
 tile(Monitor *m)
 {
-	unsigned int i, n, h, mw, my, ty;
+	unsigned int i, n, h, r, oe = enablegaps, ie = enablegaps, mw, my, ty;
 	Client *c;
 
 	for (n = 0, c = nexttiled(m->clients); c; c = nexttiled(c->next), n++);
 	if (n == 0)
 		return;
 
+	if (smartgaps == n) {
+		oe = 0; // outer gaps disabled
+	}
+
 	if (n > m->nmaster)
-		mw = m->nmaster ? m->ww * m->mfact : 0;
+		mw = m->nmaster ? (m->ww + m->gappiv*ie) * m->mfact : 0;
 	else
-		mw = m->ww;
-	for (i = my = ty = 0, c = nexttiled(m->clients); c; c = nexttiled(c->next), i++)
+		mw = m->ww - 2*m->gappov*oe + m->gappiv*ie;
+	for (i = 0, my = ty = m->gappoh*oe, c = nexttiled(m->clients); c; c = nexttiled(c->next), i++)
 		if (i < m->nmaster) {
-			h = (m->wh - my) / (MIN(n, m->nmaster) - i);
-			resize(c, m->wx, m->wy + my, mw - (2*c->bw), h - (2*c->bw), 0);
-			my += HEIGHT(c);
+			r = MIN(n, m->nmaster) - i;
+			h = (m->wh - my - m->gappoh*oe - m->gappih*ie * (r - 1)) / r;
+			resize(c, m->wx + m->gappov*oe, m->wy + my, mw - (2*c->bw) - m->gappiv*ie, h - (2*c->bw), 0);
+			my += HEIGHT(c) + m->gappih*ie;
 		} else {
-			h = (m->wh - ty) / (n - i);
-			resize(c, m->wx + mw, m->wy + ty, m->ww - mw - (2*c->bw), h - (2*c->bw), 0);
-			ty += HEIGHT(c);
+			r = n - i;
+			h = (m->wh - ty - m->gappoh*oe - m->gappih*ie * (r - 1)) / r;
+			resize(c, m->wx + mw + m->gappov*oe, m->wy + ty, m->ww - mw - (2*c->bw) - 2*m->gappov*oe, h - (2*c->bw), 0);
+			ty += HEIGHT(c) + m->gappih*ie;
 		}
 }