diff -up -x dwm -x '*.o' -x compile_commands.json dwm-6.3-orig/config.mk dwm-6.3/config.mk
--- dwm-6.3-orig/config.mk	2024-06-25 01:55:26.769203813 +0200
+++ dwm-6.3/config.mk	2024-12-15 01:12:39.132847648 +0100
@@ -24,6 +24,8 @@ FREETYPEINC = /usr/include/freetype2
 INCS = -I${X11INC} -I${FREETYPEINC}
 LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS}
 
+LIBS += -lXRes
+
 # flags
 CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_C_SOURCE=200809L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}
 #CFLAGS   = -g -std=c99 -pedantic -Wall -O0 ${INCS} ${CPPFLAGS}
diff -up -x dwm -x '*.o' -x compile_commands.json dwm-6.3-orig/dwm.c dwm-6.3/dwm.c
--- dwm-6.3-orig/dwm.c	2024-06-25 01:55:26.771203825 +0200
+++ dwm-6.3/dwm.c	2025-01-16 21:07:02.942737362 +0100
@@ -40,6 +40,7 @@
 #include <X11/extensions/Xinerama.h>
 #endif /* XINERAMA */
 #include <X11/Xft/Xft.h>
+#include <X11/extensions/XRes.h>
 
 #include "drw.h"
 #include "util.h"
@@ -49,7 +50,7 @@
 #define CLEANMASK(mask)         (mask & ~(numlockmask|LockMask) & (ShiftMask|ControlMask|Mod1Mask|Mod2Mask|Mod3Mask|Mod4Mask|Mod5Mask))
 #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]))
+#define ISVISIBLE(C)            (C->swallowed == NULL && (C->tags & C->mon->tagset[C->mon->seltags]))
 #define LENGTH(X)               (sizeof X / sizeof X[0])
 #define MOUSEMASK               (BUTTONMASK|PointerMotionMask)
 #define WIDTH(X)                ((X)->w + 2 * (X)->bw)
@@ -93,6 +94,11 @@ struct Client {
 	int bw, oldbw;
 	unsigned int tags;
 	int isfixed, isfloating, isurgent, neverfocus, oldstate, isfullscreen;
+
+	Client *swallower;
+	Client *swallowed;
+	Client *next_swallowed;
+
 	Client *next;
 	Client *snext;
 	Monitor *mon;
@@ -141,6 +147,12 @@ typedef struct {
 	int monitor;
 } Rule;
 
+typedef struct SwallowDef {
+	pid_t pid;
+	Client *swallower;
+	struct SwallowDef *next;
+} SwallowDef;
+
 /* function declarations */
 static void applyrules(Client *c);
 static int applysizehints(Client *c, int *x, int *y, int *w, int *h, int interact);
@@ -260,6 +272,8 @@ static void (*handler[LASTEvent]) (XEven
 	[PropertyNotify] = propertynotify,
 	[UnmapNotify] = unmapnotify
 };
+static Atom swallow_atom;
+static SwallowDef *swallowlist;
 static Atom wmatom[WMLast], netatom[NetLast];
 static int running = 1;
 static Cur *cursor[CurLast];
@@ -400,6 +414,69 @@ arrangemon(Monitor *m)
 		m->lt[m->sellt]->arrange(m);
 }
 
+pid_t
+wintopid(Window window) {
+  XResClientIdSpec spec;
+  spec.client = window;
+  spec.mask = XRES_CLIENT_ID_XID;
+
+  long count;
+  XResClientIdValue *output;
+  XResQueryClientIds(dpy, 1, &spec, &count, &output);
+
+  pid_t pid = -1;
+
+  for (int i = 0; i < count; ++i)
+    if (output[i].spec.mask == XRES_CLIENT_ID_PID_MASK) {
+      pid = *(pid_t *)output[i].value;
+      break;
+    }
+
+  XResClientIdsDestroy(count, output);
+
+  return pid;
+}
+
+void
+copyclientpos(Client *dst, Client *src) {
+	dst->bw = src->bw;
+	resizeclient(dst, src->x, src->y, src->w, src->h);
+	dst->oldx = src->oldx;
+	dst->oldy = src->oldy;
+	dst->oldw = src->oldw;
+	dst->oldh = src->oldh;
+	dst->oldbw = src->oldbw;
+	dst->oldstate = src->oldstate;
+	dst->isfullscreen = src->isfullscreen;
+	dst->isfloating = src->isfloating;
+	dst->tags = src->tags;
+	dst->mon = src->mon;
+}
+
+void
+checkswallowed(Client *c) {
+	pid_t pid = wintopid(c->win);
+
+	if(pid < 0) return;
+	for(SwallowDef *sd = swallowlist; sd != NULL; sd = sd->next) {
+		if(pid == sd->pid) {
+			c->swallower = sd->swallower;
+			copyclientpos(c, sd->swallower);
+
+			c->next_swallowed = c->swallower->swallowed;
+			c->swallower->swallowed = c;
+
+			c->next = c->swallower->next;
+			c->swallower->next = c;
+
+			c->snext = c->swallower->snext;
+			c->swallower->snext = c;
+
+			return;
+		}
+	}
+}
+
 void
 attach(Client *c)
 {
@@ -526,7 +603,15 @@ clientmessage(XEvent *e)
 	} else if (cme->message_type == netatom[NetActiveWindow]) {
 		if (c != selmon->sel && !c->isurgent)
 			seturgent(c, 1);
+	} else if(cme->message_type == swallow_atom) {
+		SwallowDef *node = ecalloc(1, sizeof(SwallowDef));
+		node->pid = cme->data.l[0];
+		node->swallower = c;
+		node->next = swallowlist;
+		swallowlist = node;
+		return;
 	}
+
 }
 
 void
@@ -1052,6 +1137,7 @@ manage(Window w, XWindowAttributes *wa)
 	c->y = MAX(c->y, ((c->mon->by == c->mon->my) && (c->x + (c->w / 2) >= c->mon->wx)
 		&& (c->x + (c->w / 2) < c->mon->wx + c->mon->ww)) ? bh : c->mon->my);
 	c->bw = borderpx;
+	checkswallowed(c);
 
 	wc.border_width = c->bw;
 	XConfigureWindow(dpy, w, CWBorderWidth, &wc);
@@ -1066,8 +1152,10 @@ manage(Window w, XWindowAttributes *wa)
 		c->isfloating = c->oldstate = trans != None || c->isfixed;
 	if (c->isfloating)
 		XRaiseWindow(dpy, c->win);
-	attach(c);
-	attachstack(c);
+	if(!c->swallower) {
+		attach(c);
+		attachstack(c);
+	}
 	XChangeProperty(dpy, root, netatom[NetClientList], XA_WINDOW, 32, PropModeAppend,
 		(unsigned char *) &(c->win), 1);
 	XMoveResizeWindow(dpy, c->win, c->x + 2 * sw, c->y, c->w, c->h); /* some windows require this */
@@ -1164,6 +1252,10 @@ movemouse(const Arg *arg)
 		case Expose:
 		case MapRequest:
 			handler[ev.type](&ev);
+
+			// A MapRequest could've caused the current window to swallow another one.
+			if(c->swallowed)
+				c = c->swallowed;
 			break;
 		case MotionNotify:
 			if ((ev.xmotion.time - lasttime) <= (1000 / 60))
@@ -1318,6 +1410,9 @@ resizemouse(const Arg *arg)
 		case Expose:
 		case MapRequest:
 			handler[ev.type](&ev);
+
+			if(c->swallowed)
+				c = c->swallowed;
 			break;
 		case MotionNotify:
 			if ((ev.xmotion.time - lasttime) <= (1000 / 60))
@@ -1566,6 +1661,7 @@ setup(void)
 	netatom[NetWMWindowType] = XInternAtom(dpy, "_NET_WM_WINDOW_TYPE", False);
 	netatom[NetWMWindowTypeDialog] = XInternAtom(dpy, "_NET_WM_WINDOW_TYPE_DIALOG", False);
 	netatom[NetClientList] = XInternAtom(dpy, "_NET_CLIENT_LIST", False);
+	swallow_atom = XInternAtom(dpy, "_BETTER_SWALLOW", False);
 	/* init cursors */
 	cursor[CurNormal] = drw_cur_create(drw, XC_left_ptr);
 	cursor[CurResize] = drw_cur_create(drw, XC_sizing);
@@ -1583,6 +1679,8 @@ setup(void)
 		PropModeReplace, (unsigned char *) &wmcheckwin, 1);
 	XChangeProperty(dpy, wmcheckwin, netatom[NetWMName], utf8string, 8,
 		PropModeReplace, (unsigned char *) "dwm", 3);
+	XChangeProperty(dpy, root, swallow_atom, utf8string, 8,
+		PropModeReplace, (unsigned char *) "supported", 9);
 	XChangeProperty(dpy, root, netatom[NetWMCheck], XA_WINDOW, 32,
 		PropModeReplace, (unsigned char *) &wmcheckwin, 1);
 	/* EWMH support per view */
@@ -1766,11 +1864,55 @@ unfocus(Client *c, int setfocus)
 }
 
 void
+deleteswallower(Client *c) {
+	SwallowDef **prevnext = &swallowlist;
+	for(SwallowDef *sd = swallowlist; sd != NULL;) {
+		if(sd->swallower == c) {
+			SwallowDef *next = sd->next;
+			*prevnext = next;
+			free(sd);
+			sd = next;
+		} else {
+			prevnext = &sd->next;
+			sd = sd->next;
+		}
+	}
+
+	Client *sw = c->swallowed;
+	while(sw) {
+		sw->swallower = NULL;
+		Client *next = sw->next_swallowed;
+ 		sw->next_swallowed = NULL;
+		sw = next;
+	}
+}
+
+void
 unmanage(Client *c, int destroyed)
 {
 	Monitor *m = c->mon;
 	XWindowChanges wc;
 
+	if(c->swallower) {
+		Client **prev = &c->swallower->swallowed;
+		for(; *prev != c; prev = &(*prev)->next_swallowed)
+			;
+		*prev = c->next_swallowed;
+		c->next_swallowed = NULL;
+
+		if(c->swallower->swallowed == NULL) {
+			detach(c->swallower);
+			detachstack(c->swallower);
+
+			c->swallower->next = c->next;
+			c->next = c->swallower;
+			c->swallower->snext = c->snext;
+			c->snext = c->swallower;
+
+			copyclientpos(c->swallower, c);
+		}
+	}
+
 	detach(c);
 	detachstack(c);
 	if (!destroyed) {
@@ -1783,9 +1925,10 @@ unmanage(Client *c, int destroyed)
 		XSync(dpy, False);
 		XSetErrorHandler(xerror);
 		XUngrabServer(dpy);
-	}
+	} else deleteswallower(c);
+	if(c->swallower) focus(c->swallower);
+	else focus(NULL);
 	free(c);
-	focus(NULL);
 	updateclientlist();
 	arrange(m);
 }