Adds togglable attachaside feature

config.def.h

@@ -13,6 +13,7 @@ static const int showbar = 1;				  /* 0 means no bar */
 static const int topbar = 1;				  /* 0 means bottom bar */
 static const char *fonts[] = {"Cantarell-Regular:size=12", "Fira Code Nerd Font:size=12"};
 
+static int isattachaside = 0;
 static int barheight;
 static char xresourcesfont[30];
 
@@ -327,6 +328,7 @@ static Key keys[] = {
 	{MODKEY | ShiftMask | Mod1Mask, XK_d, toggledoubledraw, {0} },
 	{MODKEY|ShiftMask, XK_w, warpfocus, {0} },
 	{MODKEY|Mod1Mask, XK_w, centerwindow, {0} },
+	{MODKEY|Mod1Mask, XK_a, toggleattachaside, {0} },
 	{MODKEY|ShiftMask|ControlMask, XK_s, toggleshowtags, { .ui = 2 } },
 	{MODKEY, XK_i, incnmaster, {.i = +1}},
 	{MODKEY, XK_d, incnmaster, {.i = -1}},

instantwm.c

@@ -757,6 +757,21 @@ attach(Client *c)
 	c->mon->clients = c;
 }
 
+void
+attachaside(Client *c) {
+    if (!isattachaside) {
+        attach(c);
+        return;
+    }
+    Client *at = nexttagged(c);
+    if(!at) {
+        attach(c);
+        return;
+    }
+    c->next = at->next;
+    at->next = c;
+}
+
 void
 attachstack(Client *c)
 {
@@ -2174,7 +2189,7 @@ manage(Window w, XWindowAttributes *wa)
 		c->isfloating = c->oldstate = trans != None || c->isfixed;
 	if (c->isfloating)
 		XRaiseWindow(dpy, c->win);
-	attach(c);
+	attachaside(c);
 	attachstack(c);
 	XChangeProperty(dpy, root, netatom[NetClientList], XA_WINDOW, 32, PropModeAppend,
 		(unsigned char *) &(c->win), 1);
@@ -3176,6 +3191,16 @@ void shutkill(const Arg *arg) {
 		killclient(arg);
 }
 
+Client *
+nexttagged(Client *c) {
+	Client *walked = c->mon->clients;
+	for(;
+		walked && (walked->isfloating || !ISVISIBLEONTAG(walked, c->tags));
+		walked = walked->next
+	);
+	return walked;
+}
+
 Client *
 nexttiled(Client *c)
 {
@@ -3725,7 +3750,7 @@ sendmon(Client *c, Monitor *m)
 	detachstack(c);
 	c->mon = m;
 	c->tags = m->tagset[m->seltags]; /* assign tags of target monitor */
-	attach(c);
+	attachaside(c);
 	attachstack(c);
 	focus(NULL);
 	arrange(NULL);
@@ -4317,6 +4342,12 @@ tagtoright(const Arg *arg) {
 
 }
 
+// toggle attach new clients to stack area
+void
+toggleattachaside(void) {
+    isattachaside = !isattachaside;
+}
+
 // toggle tag icon view
 void
 togglealttag(const Arg *arg)
@@ -4969,7 +5000,7 @@ updategeom(void)
 					m->clients = c->next;
 					detachstack(c);
 					c->mon = mons;
-					attach(c);
+					attachaside(c);
 					attachstack(c);
 				}
 				if (m == selmon)

instantwm.h

@@ -23,6 +23,7 @@
 #define INTERSECT(x,y,w,h,m)    (MAX(0, MIN((x)+(w),(m)->wx+(m)->ww) - MAX((x),(m)->wx)) \
                                * MAX(0, MIN((y)+(h),(m)->wy+(m)->wh) - MAX((y),(m)->wy)))
 #define ISVISIBLE(C)            ((C->tags & C->mon->tagset[C->mon->seltags]) || C->issticky)
+#define ISVISIBLEONTAG(C, T)    ((C->tags & T))
 #define HIDDEN(C)               ((getstate(C->win) == IconicState))
 #define LENGTH(X)               (sizeof X / sizeof X[0])
 #define MOUSEMASK               (BUTTONMASK|PointerMotionMask)
@@ -189,6 +190,7 @@ void arrange(Monitor *m);
 void arrangemon(Monitor *m);
 void resetcursor();
 void attach(Client *c);
+void attachaside(Client *c);
 void attachstack(Client *c);
 void buttonpress(XEvent *e);
 void checkotherwm(void);
@@ -244,6 +246,7 @@ void moveresize(const Arg *arg);
 void distributeclients(const Arg *arg);
 void keyresize(const Arg *arg);
 void centerwindow();
+Client *nexttagged(Client *c);
 Client *nexttiled(Client *c);
 void pop(Client *);
 void shutkill(const Arg *arg);
@@ -292,6 +295,7 @@ void tagtoleft(const Arg *arg);
 void tagtoright(const Arg *arg);
 void uppress(const Arg *arg);
 void downpress(const Arg *arg);
+void toggleattachaside(void);
 void togglealttag(const Arg *arg);
 void alttabfree(const Arg *arg);
 void toggleanimated(const Arg *arg);