LR-CROP-RECT: a too-small crop's corner drag reaches the minimum size (#2308)

The free-corner solve clamped its minimum-size bounds to zero, so a crop
already under the minimum stayed under it when a corner was dragged out
a little (2 px grew to 4 px where 8 px is the minimum). Keep the bounds
as given: the solve then grows it to the minimum, as the unrotated path
does, and falls back to that path when the minimum doesn't fit.

crates/geom/src/crop_drag.rs

@@ -236,7 +236,7 @@ fn nearest_offset(points: &[(Point, Vec2)], extra: &[(Vec2, f64)], angle: f64, w
             planes.push((n, b.max(0.0) + s));
         }
     }
-    planes.extend(extra.iter().map(|(n, b)| (*n, b.max(0.0))));
+    planes.extend_from_slice(extra);
     if planes.iter().all(|(n, b)| n.dot(want) <= *b) {
         return Some(want);
     }
@@ -707,6 +707,15 @@ mod tests {
         }
     }
 
+    //   Scenario: a free corner of a crop under the minimum size on a straightened photo
+    #[test]
+    fn given_straightened_photo_when_a_corner_of_a_too_small_crop_is_dragged_then_it_reaches_the_minimum() {
+        let start = CropGeometry { rect: Rect::new(0.3, 0.3, 0.3 + 2.0 / W, 0.6), angle: 6.0 };
+        let g = drag(start, BottomRight, p(start.rect.x1, 0.6), p(start.rect.x1 + 2.0 / W, 0.62), None);
+        assert!(g.rect.width() * W >= MIN_CROP_FRACTION * H - EPS, "{:?}", g.rect);
+        assert!(g.is_within_image(W, H) && near(g.rect.x0, 0.3) && near(g.rect.y0, 0.3), "{:?}", g.rect);
+    }
+
     //   Scenario: a free corner moved inside, or across its anchor, on a straightened photo
     #[test]
     fn given_straightened_photo_when_a_free_corner_moves_inside_then_it_follows_and_keeps_a_minimum_size() {