patch: scratchpadz

This patch enables the use of multiple pre-assigned scratchpad
terminals.  This patch uses reserved tags for stowing scratchpads, these
are the tagmasks just beyond those defined for normal use.

DWM's rule system is used to handle spawning scratchpad windows.  We use
one rule per scratchpad to define what SPTAG it belongs to, whether it
is floating, an instance identifier, and what program to exec in st
(your shell by default).  Keybinds should be setup to call togglescratch
with a pointer to the rule struct which defines the scratchpad.

The togglescratch function uses the information in the rule to craft an
st command line to spawn.  However, if some client is already open on
the rule's tagmask, it will just act like toggleview(tagmask).

Normal clients may be opened while viewing scratchpads, they are always
excluded from scratchpad tags.

This patch is inspired by the "scratchpad" and "scratchpads" patches
from suckless.org.

2 files changed, 53 insertions, 4 deletions

diff --git a/config.def.h b/config.def.h
index d969b02..fe50ff3 100644
--- a/config.def.h
+++ b/config.def.h
@@ -24,13 +24,16 @@ static const char *colors[][3]      = {
 static const char *tags[] = { "1", "2", "3", "4", "5", "6", "7", "8", "9", "0" };
 static const char *tagfmt = "[%s: %.30s]";
 
+static const char *scratchpad_size = "120x34";
 static const Rule rules[] = {
 	/* xprop(1):
 	 *	WM_CLASS(STRING) = instance, class
 	 *	WM_NAME(STRING) = title
 	 */
-	/* class      instance    title       tags mask     isfloating   monitor */
-	{  NULL,      NULL,       NULL,       0,            0,           -1 },
+	/* class      instance    title       tags mask     isfloating   monitor   scratchpad exec */
+	{ "st",       "sp-shell", NULL,       SPTAG(0),     1,           -1,       NULL },
+	{ "st",       "sp-pythn", NULL,       SPTAG(1),     1,           -1,       "ipython3" },
+	{ "st",       "sp-mixer", NULL,       SPTAG(2),     1,           -1,       "alsamixer" },
 };
 
 /* layout(s) */
@@ -109,6 +112,9 @@ static const Key keys[] = {
 	{ MODKEY,                       XK_period, focusmon,       {.i = +1 } },
 	{ MODKEY|ShiftMask,             XK_comma,  tagmon,         {.i = -1 } },
 	{ MODKEY|ShiftMask,             XK_period, tagmon,         {.i = +1 } },
+	{ MODKEY,                       XK_grave,  togglescratch,  {.v = &rules[0]} },
+	{ MODKEY,                       XK_equal,  togglescratch,  {.v = &rules[1]} },
+	{ MODKEY,                       XK_minus,  togglescratch,  {.v = &rules[2]} },
 	TAGKEYS(                        XK_1,                      0)
 	TAGKEYS(                        XK_2,                      1)
 	TAGKEYS(                        XK_3,                      2)
diff --git a/dwm.c b/dwm.c
index d8f0f96..b253eb3 100644
--- a/dwm.c
+++ b/dwm.c
@@ -53,7 +53,9 @@
 #define MOUSEMASK               (BUTTONMASK|PointerMotionMask)
 #define WIDTH(X)                ((X)->w + 2 * (X)->bw)
 #define HEIGHT(X)               ((X)->h + 2 * (X)->bw)
-#define TAGMASK                 ((1 << LENGTH(tags)) - 1)
+#define TAGMASK                 (~0)
+#define SPTAG(X)                (1 << (LENGTH(tags) + (X)))
+#define SPTAGMASK               (~0 << LENGTH(tags))
 #define TEXTW(X)                (drw_fontset_getwidth(drw, (X)) + lrpad)
 
 #define OPAQUE                  0xffU
@@ -144,6 +146,7 @@ typedef struct {
 	unsigned int tags;
 	int isfloating;
 	int monitor;
+	const char *scratchpad_exec;
 } Rule;
 
 /* function declarations */
@@ -225,6 +228,7 @@ static void tile(Monitor *m);
 static void togglebar(const Arg *arg);
 static void holdbar(const Arg *arg);
 static void togglefloating(const Arg *arg);
+static void togglescratch(const Arg *arg);
 static void toggletag(const Arg *arg);
 static void toggleview(const Arg *arg);
 static void unfocus(Client *c, int setfocus);
@@ -379,6 +383,10 @@ applyrules(Client *c)
 		{
 			c->isfloating = r->isfloating;
 			c->tags |= r->tags;
+			if ((r->tags & SPTAGMASK) && r->isfloating) {
+				c->x = c->mon->wx + (c->mon->ww / 2 - WIDTH(c) / 2);
+				c->y = c->mon->wy + (c->mon->wh / 2 - HEIGHT(c) / 2);
+			}
 			for (m = mons; m && m->num != r->monitor; m = m->next);
 			if (m)
 				c->mon = m;
@@ -388,7 +396,7 @@ applyrules(Client *c)
 		XFree(ch.res_class);
 	if (ch.res_name)
 		XFree(ch.res_name);
-	c->tags = c->tags & TAGMASK ? c->tags & TAGMASK : c->mon->tagset[c->mon->seltags];
+	c->tags = c->tags & TAGMASK ? c->tags & TAGMASK : (c->mon->tagset[c->mon->seltags] & ~SPTAGMASK);
 }
 
 int
@@ -1994,6 +2002,41 @@ togglefloating(const Arg *arg)
 }
 
 void
+togglescratch(const Arg *arg)
+{
+	const Rule *sp = arg->v;
+
+	unsigned int found = 0;
+	unsigned int scratchtag = sp->tags;
+	Client *c;
+
+	for (c = selmon->clients; c && !(found = c->tags & scratchtag); c = c->next) {}
+
+	if (found) {
+		unsigned int newtagset = selmon->tagset[selmon->seltags] ^ scratchtag;
+		if (newtagset) {
+			selmon->tagset[selmon->seltags] = newtagset;
+			focus(NULL);
+			arrange(selmon);
+		}
+		if (ISVISIBLE(c)) {
+			focus(c);
+			restack(selmon);
+		}
+	} else {
+		const char *exec[] = { "st", "-n", sp->instance, "-g", scratchpad_size, NULL, NULL, NULL };
+		if (sp->scratchpad_exec) {
+			exec[5] = "-e";
+			exec[6] = sp->scratchpad_exec;
+		}
+
+		Arg execarg = {.v = exec};
+		selmon->tagset[selmon->seltags] |= scratchtag;
+		spawn(&execarg);
+	}
+}
+
+void
 toggletag(const Arg *arg)
 {
 	unsigned int newtags;