Added clickable button on left side of the bar

config.def.h

@@ -5,6 +5,7 @@ static const unsigned int borderpx  = 1;        /* border pixel of windows */
 static const unsigned int snap      = 32;       /* snap pixel */
 static const int showbar            = 1;        /* 0 means no bar */
 static const int topbar             = 1;        /* 0 means bottom bar */
+static const char buttonbar[]       = "<O>";
 static const char *fonts[]          = { "monospace:size=10" };
 static const char dmenufont[]       = "monospace:size=10";
 static const char col_gray1[]       = "#222222";
@@ -100,6 +101,7 @@ static Key keys[] = {
 /* click can be ClkTagBar, ClkLtSymbol, ClkStatusText, ClkWinTitle, ClkClientWin, or ClkRootWin */
 static Button buttons[] = {
 	/* click                event mask      button          function        argument */
+	{ ClkButton,		    0,		        Button1,	    spawn,		    {.v = dmenucmd } },
 	{ ClkLtSymbol,          0,              Button1,        setlayout,      {0} },
 	{ ClkLtSymbol,          0,              Button3,        setlayout,      {.v = &layouts[2]} },
 	{ ClkWinTitle,          0,              Button2,        zoom,           {0} },

dwm.c

@@ -64,7 +64,7 @@ enum { NetSupported, NetWMName, NetWMState, NetWMCheck,
        NetWMFullscreen, NetActiveWindow, NetWMWindowType,
        NetWMWindowTypeDialog, NetClientList, NetLast }; /* EWMH atoms */
 enum { WMProtocols, WMDelete, WMState, WMTakeFocus, WMLast }; /* default atoms */
-enum { ClkTagBar, ClkLtSymbol, ClkStatusText, ClkWinTitle,
+enum { ClkTagBar, ClkLtSymbol, ClkStatusText, ClkButton, ClkWinTitle,
        ClkClientWin, ClkRootWin, ClkLast }; /* clicks */
 
 typedef union {
@@ -432,18 +432,23 @@ buttonpress(XEvent *e)
 	}
 	if (ev->window == selmon->barwin) {
 		i = x = 0;
-		do
-			x += TEXTW(tags[i]);
-		while (ev->x >= x && ++i < LENGTH(tags));
-		if (i < LENGTH(tags)) {
-			click = ClkTagBar;
-			arg.ui = 1 << i;
-		} else if (ev->x < x + blw)
-			click = ClkLtSymbol;
-		else if (ev->x > selmon->ww - TEXTW(stext))
-			click = ClkStatusText;
-		else
-			click = ClkWinTitle;
+		x += TEXTW(buttonbar);
+		if(ev->x < x) {
+			click = ClkButton;
+		} else {
+			do
+				x += TEXTW(tags[i]);
+			while (ev->x >= x && ++i < LENGTH(tags));
+			if (i < LENGTH(tags)) {
+				click = ClkTagBar;
+				arg.ui = 1 << i;
+			} else if (ev->x < x + blw)
+				click = ClkLtSymbol;
+			else if (ev->x > selmon->ww - TEXTW(stext))
+				click = ClkStatusText;
+			else
+				click = ClkWinTitle;
+		}
 	} else if ((c = wintoclient(ev->window))) {
 		focus(c);
 		restack(selmon);
@@ -715,6 +720,9 @@ drawbar(Monitor *m)
 			urg |= c->tags;
 	}
 	x = 0;
+	w = blw = TEXTW(buttonbar);
+	drw_setscheme(drw, scheme[SchemeNorm]);
+	x = drw_text(drw, x, 0, w, bh, lrpad / 2, buttonbar, 0);
 	for (i = 0; i < LENGTH(tags); i++) {
 		w = TEXTW(tags[i]);
 		drw_setscheme(drw, scheme[m->tagset[m->seltags] & 1 << i ? SchemeSel : SchemeNorm]);