dwm: Add save floats patch

Now it's possible to float and unfloat windows and those windows will
preserve their floating window size.

Note that this patch was merged with the alwayscenter patch so the diff
applies cleanly.

assets/dwm-savefloats-alwayscenter.patch

@@ -0,0 +1,44 @@
+diff --git a/dwm.c b/dwm.c
+index 67c6b2b..ed46374 100644
+--- a/dwm.c
++++ b/dwm.c
+@@ -88,6 +88,7 @@ struct Client {
+ 	char name[256];
+ 	float mina, maxa;
+ 	int x, y, w, h;
++	int sfx, sfy, sfw, sfh; /* stored float geometry, used on mode revert */
+ 	int oldx, oldy, oldw, oldh;
+ 	int basew, baseh, incw, inch, maxw, maxh, minw, minh, hintsvalid;
+ 	int bw, oldbw;
+@@ -1068,6 +1069,12 @@ manage(Window w, XWindowAttributes *wa)
+ 	updatewindowtype(c);
+ 	updatesizehints(c);
+ 	updatewmhints(c);
++	c->x = c->mon->mx + (c->mon->mw - WIDTH(c)) / 2;
++	c->y = c->mon->my + (c->mon->mh - HEIGHT(c)) / 2;
++	c->sfx = c->x;
++	c->sfy = c->y;
++	c->sfw = c->w;
++	c->sfh = c->h;
+ 	XSelectInput(dpy, w, EnterWindowMask|FocusChangeMask|PropertyChangeMask|StructureNotifyMask);
+ 	grabbuttons(c, 0);
+ 	if (!c->isfloating)
+@@ -1730,8 +1737,16 @@ togglefloating(const Arg *arg)
+ 		return;
+ 	selmon->sel->isfloating = !selmon->sel->isfloating || selmon->sel->isfixed;
+ 	if (selmon->sel->isfloating)
+-		resize(selmon->sel, selmon->sel->x, selmon->sel->y,
+-			selmon->sel->w, selmon->sel->h, 0);
++		/* restore last known float dimensions */
++		resize(selmon->sel, selmon->sel->sfx, selmon->sel->sfy,
++		       selmon->sel->sfw, selmon->sel->sfh, False);
++	else {
++		/* save last known float dimensions */
++		selmon->sel->sfx = selmon->sel->x;
++		selmon->sel->sfy = selmon->sel->y;
++		selmon->sel->sfw = selmon->sel->w;
++		selmon->sel->sfh = selmon->sel->h;
++	}
+ 	arrange(selmon);
+ }
+ 

specializations/dwm.nix

@@ -256,17 +256,13 @@ in
             ../assets/dwm-adjacenttag.patch
             ../assets/dwm-remove-layout-indicator.patch
             ../assets/dwm-remove-floating-indicator.patch
+            ../assets/dwm-savefloats-alwayscenter.patch
 
             (pkgs.fetchpatch {
               url = "https://dwm.suckless.org/patches/hide_vacant_tags/dwm-hide_vacant_tags-6.4.diff";
               hash = "sha256-GIbRW0Inwbp99rsKLfIDGvPwZ3pqihROMBp5vFlHx5Q=";
             })
 
-            (pkgs.fetchpatch {
-              url = "https://dwm.suckless.org/patches/alwayscenter/dwm-alwayscenter-20200625-f04cac6.diff";
-              hash = "sha256-xQEwrNphaLOkhX3ER09sRPB3EEvxC73oNWMVkqo4iSY=";
-            })
-
             (pkgs.fetchpatch {
               url = "https://dwm.suckless.org/patches/alpha/dwm-alpha-20230401-348f655.diff";
               hash = "sha256-ZhuqyDpY+nQQgrjniQ9DNheUgE9o/MUXKaJYRU3Uyl4=";