From 2ed6f512eea50a0a0f0fef5e08a10859509e6587 Mon Sep 17 00:00:00 2001
From: Fini <fini.yang@gmail.com>
Date: Sun, 12 Jul 2026 13:21:34 +0800
Subject: [PATCH] feat(canvas): halo outline and fattened rounded pencil

User-picked O4 treatment: a wide translucent slate halo OUTSIDE the
white rim keeps the cursor silhouette readable on light designs while
the white edge stays crisp on dark ones (contact shadow relaxed to
compensate). The default rounded silhouette is additionally fattened
1.28x across the pencil axis with the tip hotspot fixed.
---
 .../src/widgets/canvas_agent_cursor.rs        | 78 ++++++++++++-------
 1 file changed, 48 insertions(+), 30 deletions(-)

diff --git a/crates/op-editor-ui/src/widgets/canvas_agent_cursor.rs b/crates/op-editor-ui/src/widgets/canvas_agent_cursor.rs
index d71f513b5..2ec171f4b 100644
--- a/crates/op-editor-ui/src/widgets/canvas_agent_cursor.rs
+++ b/crates/op-editor-ui/src/widgets/canvas_agent_cursor.rs
@@ -209,6 +209,15 @@ pub(crate) fn silhouette_for(style: op_editor_core::PencilCursorStyle) -> Silhou
 
 /// Fallback for reveals not owned by any tagged agent (the same red the
 /// retired dashed-reveal border used as its untagged default).
+/// O4 outline halo — near-black slate, drawn wide and translucent
+/// OUTSIDE the white rim.
+const PENCIL_HALO: Color = Color {
+    r: 0.067,
+    g: 0.094,
+    b: 0.153,
+    a: 1.0,
+};
+
 /// Chubby variant's eraser butt.
 const PENCIL_ERASER_PINK: Color = Color {
     r: 1.0,
@@ -231,52 +240,53 @@ const FALLBACK_COLOR: Color = Color {
 /// `PENCIL_TIP_POINTS`). Anatomy mirrors Pencil's multiplayer cursor
 /// (solid tinted pointer + name pill) without copying its arrow.
 ///
-/// ROUNDED variant (user-picked "B", 2026-07-12): every corner of the
+/// ROUNDED variant (user-picked "B", then fattened 1.28x across the
+/// pencil axis with the tip hotspot fixed - "加胖更可爱", 2026-07-12): every corner of the
 /// straight-edged silhouette is a quadratic arc — round shoulders at the
 /// eraser butt, a curved collar, a soft tip wedge. The arcs are baked
 /// as dense polygon samples so the existing polygon painters render
 /// them smoothly with no new backend primitive.
 const ROUNDED_BODY: [(f32, f32); 19] = [
-    (0.00, 0.00), // graphite tip (hotspot)
-    (7.60, 2.00),
-    (8.11, 2.18),
-    (8.58, 2.44),
-    (9.00, 2.80),
-    (20.00, 13.80),
-    (20.60, 14.63),
-    (20.80, 15.50),
-    (20.60, 16.43),
-    (20.00, 17.40),
-    (17.40, 20.00),
-    (16.43, 20.60),
-    (15.50, 20.80),
-    (14.62, 20.60),
-    (13.80, 20.00),
-    (2.80, 9.00),
-    (2.44, 8.58),
-    (2.18, 8.11),
-    (2.00, 7.60),
+    (0.00, 0.00),
+    (8.38, 1.22),
+    (8.94, 1.35),
+    (9.44, 1.58),
+    (9.87, 1.93),
+    (20.87, 12.93),
+    (21.44, 13.79),
+    (21.54, 14.76),
+    (21.18, 15.85),
+    (20.36, 17.04),
+    (17.04, 20.36),
+    (15.85, 21.18),
+    (14.76, 21.54),
+    (13.78, 21.44),
+    (12.93, 20.87),
+    (1.93, 9.87),
+    (1.58, 9.44),
+    (1.35, 8.94),
+    (1.22, 8.38),
 ];
 
 /// White wedge over the tip — the sharpened-graphite highlight, with a
 /// curved base matching the rounded collar.
 const ROUNDED_TIP: [(f32, f32); 6] = [
     (0.00, 0.00),
-    (4.40, 1.20),
-    (3.53, 1.92),
+    (4.85, 0.75),
+    (3.76, 1.69),
     (2.70, 2.70),
-    (1.92, 3.53),
-    (1.20, 4.40),
+    (1.69, 3.76),
+    (0.75, 4.85),
 ];
 
 /// Collar seam between the sharpened cone and the painted body — a soft
 /// arc sampled as a short polyline.
 const ROUNDED_COLLAR: [(f32, f32); 5] = [
-    (2.00, 7.60),
-    (3.48, 6.12),
-    (4.90, 4.70),
-    (6.27, 3.32),
-    (7.60, 2.00),
+    (1.22, 8.38),
+    (3.11, 6.49),
+    (4.93, 4.67),
+    (6.68, 2.91),
+    (8.38, 1.22),
 ];
 
 /// A scheduled placement the cursor must reach: one generated node's
@@ -632,6 +642,8 @@ pub(crate) fn paint_cursor_swatch(
             .map(|(dx, dy)| Point2D::new(origin.x + dx, origin.y + dy))
             .collect()
     };
+    cx.backend
+        .stroke_polygon(&at(silhouette.body), PENCIL_HALO.with_alpha(0.28), 4.5);
     cx.backend.fill_polygon(&at(silhouette.body), color);
     cx.backend
         .stroke_polygon(&at(silhouette.body), Color::WHITE.with_alpha(0.9), 1.2);
@@ -682,7 +694,13 @@ fn paint_sprite(cx: &mut PaintCx<'_>, sprite: &CursorSprite, now_ms: u64, silhou
         .map(|p| Point2D::new(p.x + 1.0, p.y + 1.5))
         .collect();
     cx.backend
-        .fill_polygon(&shadow, Color::BLACK.with_alpha(0.18 * sprite.alpha));
+        .fill_polygon(&shadow, Color::BLACK.with_alpha(0.14 * sprite.alpha));
+    // Dark halo OUTSIDE the white outline (user-picked "O4", the macOS
+    // pointer treatment): a pure-white outline vanished on light designs;
+    // the wide low-alpha dark ring keeps the silhouette readable on any
+    // ground while the white rim keeps it crisp on dark ones.
+    cx.backend
+        .stroke_polygon(&body, PENCIL_HALO.with_alpha(0.28 * sprite.alpha), 5.4);
     cx.backend
         .fill_polygon(&body, sprite.color.with_alpha(sprite.alpha));
     cx.backend