fix: improve resize edge stability

Author: dy-tea

TODO.md

@@ -2,7 +2,6 @@
 - Per-window animation overrides
 - Ensure animations and blur work together without visual artifacts
 - Custom animation shaders for windows (e.g. open/close animations)
-- Tiled and interactive resize does not have stable position (edge(s) that should not move do(es) not have stable position), specifically for undersized surfaces (surfaces that are smaller than their allocated size)
 - Floating toplevels do not animate their position on workspace switch
 
 # Effects

src/animation.c

@@ -694,27 +694,22 @@ static void update_resize_entry(animation_entry_t *entry) {
 		if (IS_TILED(c) || c->state == STATE_FLOATING || c->state == STATE_FULLSCREEN) {
 			int geo_w = (int)entry->toplevel->geometry.width;
 			int geo_h = (int)entry->toplevel->geometry.height;
-			bool undersized = geo_w < entry->to.width || geo_h < entry->to.height;
 
+			// always honour anchored edges, even for undersized surfaces
 			int cx, cy;
-			if (undersized) {
+			if (entry->from.x == entry->to.x)
+				cx = 0;
+			else if (from_right == to_right)
+				cx = width - geo_w;
+			else
 				cx = (width - geo_w) / 2;
+
+			if (entry->from.y == entry->to.y)
+				cy = 0;
+			else if (from_bottom == to_bottom)
+				cy = height - geo_h;
+			else
 				cy = (height - geo_h) / 2;
-			} else {
-				if (entry->from.x == entry->to.x)
-					cx = 0;
-				else if (from_right == to_right)
-					cx = width - geo_w;
-				else
-					cx = (width - geo_w) / 2;
-
-				if (entry->from.y == entry->to.y)
-					cy = 0;
-				else if (from_bottom == to_bottom)
-					cy = height - geo_h;
-				else
-					cy = (height - geo_h) / 2;
-			}
 
 			if (cx < 0)
 				cx = 0;