gave up and limited recursion depth

kiln-core/src/board.rs

@@ -112,16 +112,16 @@ impl Board {
     ///
     /// With a single grid the draw order is a fixed precedence (no layer walk):
     ///
-    /// 1. the player (drawn on top; not part of the grid yet);
-    /// 2. an object at the cell — a solid object always, otherwise the first
-    ///    non-transparent non-solid object (`tile != 0`, so invisible objects exist);
-    /// 3. the grid cell `(glyph, arch)` — a solid always draws, a non-solid only when
-    ///    visible (`tile != 0`);
-    /// 4. a portal at the cell (portals sit on a transparent grid cell);
-    /// 5. a [`decoration`](Board::decorations) at the cell (reached only because the
-    ///    grid cell was empty);
-    /// 6. the [`floor`](Board::floor) glyph, if any;
-    /// 7. the canonical black `Empty` glyph.
+    /// 1. a sensor `Above` the grid whose glyph is visible (drawn on top of the
+    ///    player too);
+    /// 2. the grid cell's tile — the player or an object — when its glyph is
+    ///    visible (`tile != 0`, so invisible objects exist);
+    /// 3. a sensor `Below` the grid whose glyph is visible (only reachable
+    ///    because the grid cell drew nothing);
+    /// 4. a portal at the cell (portals sit on a transparent grid cell), when
+    ///    its glyph is visible;
+    /// 5. the [`floor`](Board::floor) glyph, if any;
+    /// 6. the canonical black `Empty` glyph.
     ///
     /// Panics if out of bounds.
     pub fn glyph_at<P: Into<Point>>(&self, p: P) -> Glyph {
@@ -145,6 +145,12 @@ impl Board {
             return below.scripting.glyph;
         }
 
+        // A portal at the cell, if its glyph is visible (a `tile = 0` portal is
+        // deliberately invisible, so the floor shows through instead).
+        if let Some(portal) = self.portal_at(p) && portal.glyph.is_visible() {
+            return portal.glyph;
+        }
+
         // Otherwise the floor, or the canonical black empty cell.
         self.floor.glyph_at(p, self.width).unwrap_or_else(Glyph::transparent)
     }