From 4c088c32846b989ce4b631d504dc135459533e89 Mon Sep 17 00:00:00 2001
From: Michael Anderson <andermic@gmail.com>
Date: Tue, 13 Oct 2026 07:15:32 -0500
Subject: [PATCH] Never crash: Give the loupe a finite aspect for a zero-size
 crop

Count each side as at least one pixel.
---
 crates/pipeline/src/geometry.rs  | 25 +++++++++++++++++++++++--
 crates/ui-egui/src/tests_zoom.rs | 27 +++++++++++++++++++++++++++
 docs/whats-new.md                |  4 ++++
 3 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/crates/pipeline/src/geometry.rs b/crates/pipeline/src/geometry.rs
index bea792c19..5e35a0552 100644
--- a/crates/pipeline/src/geometry.rs
+++ b/crates/pipeline/src/geometry.rs
@@ -167,10 +167,12 @@ impl Frame {
         }
     }
 
-    /// Aspect ratio (w/h) of the output.
+    /// Aspect ratio (w/h) of the output. A crop narrower than a source pixel (or of no size, from
+    /// an agent or a sidecar) counts each side as one pixel, so the aspect stays finite: 0/0 made
+    /// it NaN, and the loupe laid the photo out at a NaN size.
     pub fn aspect(&self) -> f64 {
         let r = self.crop.rect_px(self.ow, self.oh);
-        r.width() / r.height()
+        r.width().max(1.0) / r.height().max(1.0)
     }
 
     /// Size of the (cropped) output at the source's own resolution, in pixels.
@@ -383,6 +385,25 @@ mod tests {
         assert!((back.x - 50.0).abs() < 1e-6 && (back.y - 50.0).abs() < 1e-6);
     }
 
+    /// A crop of no size (or under a pixel wide) gave a NaN or infinite aspect; each side now
+    /// counts as at least one source pixel.
+    #[test]
+    fn degenerate_crops_have_a_finite_aspect() {
+        let mut s = DevelopSettings::default();
+        for (rect, want) in [
+            (Rect::new(0.5, 0.5, 0.5, 0.5), 1.0),
+            (Rect::new(0.0, 0.0, 1e-9, 1.0), 1.0 / 200.0),
+            (Rect::new(0.0, 0.5, 1.0, 0.5), 400.0),
+            (Rect::new(0.25, 0.0, 0.75, 1.0), 1.0),
+        ] {
+            s.crop.geometry.rect = rect;
+            let f = Frame::new(400, 200, &s, true);
+            assert!((f.aspect() - want).abs() < 1e-9, "{rect:?}: {}", f.aspect());
+            let (w, h) = f.fit(1000, 1000);
+            assert!((1..=1000).contains(&w) && (1..=1000).contains(&h), "{rect:?}: {w}×{h}");
+        }
+    }
+
     #[test]
     fn flip_mirrors() {
         let mut s = DevelopSettings::default();
diff --git a/crates/ui-egui/src/tests_zoom.rs b/crates/ui-egui/src/tests_zoom.rs
index ddea400d0..b0595d27d 100644
--- a/crates/ui-egui/src/tests_zoom.rs
+++ b/crates/ui-egui/src/tests_zoom.rs
@@ -108,3 +108,30 @@ fn zoomed_before_after_views_stay_in_their_panes() {
         }
     }
 }
+
+/// A crop of no size (or a hair wide), from an agent or a sidecar, gave the loupe a NaN aspect:
+/// the photo was laid out at a NaN size, which egui's debug checks stop on (a panic in a debug
+/// build) and nothing could be drawn or clicked. It now lays out at a finite size, fitted and at
+/// 100 %.
+#[test]
+fn a_crop_of_no_size_lays_out_at_a_finite_size() {
+    let mut h = detail();
+    for rect in [[0.5, 0.5, 0.5, 0.5], [0.0, 0.0, 1e-9, 1.0], [0.0, 0.3, 1.0, 0.3]] {
+        let r = h.request("engine.execute", json!({"command": "crop.set", "params": {"rect": rect}}), T);
+        assert_eq!(r["ok"], true, "{r}");
+        for zoom in ["view.zoomFit", "view.zoom100"] {
+            let r = h.request("engine.execute", json!({"command": zoom}), T);
+            assert_eq!(r["ok"], true, "{zoom}: {r}");
+            h.settle(SETTLE);
+            let img = h.app.image_rect.expect("the loupe laid the photo out");
+            assert!(img.min.is_finite() && img.max.is_finite(), "{rect:?} at {zoom}: {img:?}");
+            let r = h.request(
+                "ui.pointer",
+                json!({"events": [{"kind": "down", "x": 0.5, "y": 0.5}, {"kind": "drag", "x": 0.6, "y": 0.4}, {"kind": "up", "x": 0.6, "y": 0.4}]}),
+                T,
+            );
+            assert_eq!(r["ok"], true, "{r}");
+            h.step();
+        }
+    }
+}
diff --git a/docs/whats-new.md b/docs/whats-new.md
index b5c2ac68c..e3661749c 100644
--- a/docs/whats-new.md
+++ b/docs/whats-new.md
@@ -2,6 +2,10 @@
 
 ## 2026-10-13
 
+### Reliability
+- A crop of no size (from an agent or a sidecar) no longer gives the Detail view a photo of no size to lay out
+  (its width over its height was 0 / 0, which stopped debug builds); it shows as a single pixel's colour.
+
 ### Slider drags on large raws
 - Dragging a slider no longer re-renders the edited photo's filmstrip thumbnail on every frame; it follows once you
   let go. On a 64 MP raw the first of those renders decoded the whole file again, which held up the loupe's