Media: a shaped corner follows the pointer up and down; the fitted crop is told once

With an aspect, a corner drag sizes the crop by whichever side the pointer
moved further, so a drag straight up or down resizes it too. The upload
tells the host the fitted crop once per file, whether the host keeps it or
not; a host that dropped it had set off a loop of reports. The annotator's
Escape stops only when it lets a chosen mark go.

src/media/crop.rs

@@ -72,7 +72,7 @@ pub(crate) fn grip_at(crop: Crop, at: (f32, f32), reach: (f32, f32), shaped: boo
     }
 }
 
-/// The crop after `grip` moves by `by`, in shares, kept inside the picture with sides of at least `least`. With `shape`, a width over height in shares, only corners resize and the box keeps that shape, anchored at the opposite corner.
+/// The crop after `grip` moves by `by`, in shares, kept inside the picture with sides of at least `least`. With `shape`, a width over height in shares, only corners resize and the box keeps that shape, anchored at the opposite corner, sized by whichever side the pointer moved further.
 pub(crate) fn dragged(
     crop: Crop,
     grip: Grip,
@@ -108,7 +108,13 @@ pub(crate) fn dragged(
     if let Some(shape) = shape {
         let tall = if grip.top { y2 } else { 1.0 - y1 };
         let wide = if grip.left { x2 } else { 1.0 - x1 };
-        let w = (x2 - x1)
+        let (across, down) = (x2 - x1, (y2 - y1) * shape);
+        let asked = if (across - crop.w).abs() >= (down - crop.w).abs() {
+            across
+        } else {
+            down
+        };
+        let w = asked
             .max(least * shape.max(1.0))
             .min(tall * shape)
             .min(wide);
@@ -252,6 +258,39 @@ mod tests {
         assert_eq!(dragged(HALF, edge, (0.0, -0.1), 0.05, Some(1.0)), HALF);
     }
 
+    #[test]
+    fn a_shaped_corner_follows_the_pointer_up_and_down_too() {
+        let bottom_right = Grip {
+            right: true,
+            bottom: true,
+            ..Grip::default()
+        };
+        let down = dragged(HALF, bottom_right, (0.0, 0.2), 0.05, Some(1.0));
+        assert!(
+            near(
+                down,
+                Crop {
+                    w: 0.7,
+                    h: 0.7,
+                    ..HALF
+                }
+            ),
+            "straight down grows it: {down:?}"
+        );
+        let up = dragged(HALF, bottom_right, (0.0, -0.2), 0.05, Some(1.0));
+        assert!(
+            near(
+                up,
+                Crop {
+                    w: 0.3,
+                    h: 0.3,
+                    ..HALF
+                }
+            ),
+            "straight up shrinks it: {up:?}"
+        );
+    }
+
     #[test]
     fn a_new_shape_takes_the_largest_centered_box_inside() {
         let wide = fitted(HALF, 2.0);