View cube edges are targets: hovering an edge lights a band along it on both faces it joins, and a click turns the view halfway between those faces (top-front looks down at 45°, front-right along the diagonal). The cube now has 26 targets (6 faces, 12 edges, 8 corner facets); its drawing is unchanged. Looking straight at a face, the four edges around it are bands along its border. Tests: every target's patches are hit where drawn, the patches cover the drawn cube from any direction, edges pick from an iso view and face-on, and the s39 scenario hovers and clicks edges

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/tests/scenarios/s39_view_cube_hover.json

@@ -1,19 +1,28 @@
 [
- {"note": "The view cube is a cube with chamfered corners. Its targets are the 6 faces and the 8 corner facets; hover lights exactly the one under the pointer (edges are not targets: a point on an edge goes to a neighbour), and a click turns the view to it."},
+ {"note": "The view cube is a cube with chamfered corners. Its targets are the 6 faces, the 12 edges (a band along each edge, on both faces it joins) and the 8 corner facets; hover lights exactly the one under the pointer, and a click turns the view to it."},
  {"call": "ui.view", "params": {"view": "home"}},
  {"move": {"cube": [0, 0, 1]}},
  {"expect": {"count": {"name": "cube_highlights", "value": 1}, "shown_handles": ["cube_hover:top"]}},
  {"move": {"cube": [0.3, -1, 0.2]}},
  {"expect": {"count": {"name": "cube_highlights", "value": 1}, "shown_handles": ["cube_hover:front"]}},
- {"note": "On the top-front edge: one target, the top or the front face."},
+ {"note": "On the top-front edge, and just off it on the top face: the edge."},
  {"move": {"cube": [0, -1, 1]}},
- {"expect": {"count": {"name": "cube_highlights", "value": 1}}},
+ {"expect": {"count": {"name": "cube_highlights", "value": 1}, "shown_handles": ["cube_hover:top-front"]}},
+ {"move": {"cube": [0, -0.9, 1]}},
+ {"expect": {"count": {"name": "cube_highlights", "value": 1}, "shown_handles": ["cube_hover:top-front"]}},
  {"move": {"cube": [0.873, -0.873, 0.873]}},
  {"expect": {"count": {"name": "cube_highlights", "value": 1}, "shown_handles": ["cube_hover:top-front-right"]}},
  {"click": {"handle": "cube:top-front-right"}},
  {"expect": {"camera": {"yaw_deg": -45, "pitch_deg": 35.26}}},
  {"click": {"handle": "cube:front"}},
  {"expect": {"camera": {"yaw_deg": 0, "pitch_deg": 0}}},
+ {"note": "Looking straight at FRONT, its top edge is a band along the face's top: it turns to the view halfway between FRONT and TOP."},
+ {"move": {"cube": [0, -1, 0.95]}},
+ {"expect": {"count": {"name": "cube_highlights", "value": 1}, "shown_handles": ["cube_hover:top-front"]}},
+ {"click": {"handle": "cube:top-front"}},
+ {"expect": {"camera": {"yaw_deg": 0, "pitch_deg": 45}}},
+ {"click": {"handle": "cube:front-right"}},
+ {"expect": {"camera": {"yaw_deg": -45, "pitch_deg": 0}}},
  {"call": "ui.view", "params": {"view": "home"}},
  {"click": {"handle": "cube:top-back-right"}},
  {"expect": {"camera": {"yaw_deg": -135, "pitch_deg": 35.26}}},