From d041bea32ad0d4ef99b8cb82f1467789ab9c0249 Mon Sep 17 00:00:00 2001
From: Hakan Seven <hakanseven8125@gmail.com>
Date: Wed, 17 Jun 2026 04:56:42 +0300
Subject: [PATCH] =?UTF-8?q?fix(snap):=20shrink=20OSNAP=20pickup=20radius?=
 =?UTF-8?q?=20to=20=C2=BC=20of=20crosshair=20arm?=
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OSNAP registered snapping over the full crosshair-arm radius (60 px),
making it too easy to snap and leaving little room to click just outside
a snap point. Split out a dedicated osnap_radius_px (¼ of the arm) used
only for object-snap matching; tracking, polar and extension pickup keep
the larger snap_radius_px.

Closes #108

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 src/snap/mod.rs | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/snap/mod.rs b/src/snap/mod.rs
index 0bed7f700..62f835021 100644
--- a/src/snap/mod.rs
+++ b/src/snap/mod.rs
@@ -87,8 +87,11 @@ pub struct Snapper {
     pub enabled: HashSet<SnapType>,
     /// World-space grid spacing.
     pub grid_spacing: f32,
-    /// Pixel-radius threshold.
+    /// Pixel-radius threshold for tracking / polar / extension pickup.
     pub snap_radius_px: f32,
+    /// Pixel-radius threshold for object snapping (OSNAP). Kept smaller than
+    /// `snap_radius_px` so it is easy to click just outside a snap point.
+    pub osnap_radius_px: f32,
     /// Object Snap Tracking on/off (F11).
     pub otrack_enabled: bool,
     /// Acquired OST points (world XZ, Y=0 plane).
@@ -114,6 +117,7 @@ impl Default for Snapper {
             enabled,
             grid_spacing: 1.0,
             snap_radius_px: CROSSHAIR_ARM,
+            osnap_radius_px: CROSSHAIR_ARM * 0.25,
             otrack_enabled: false,
             tracking_points: Vec::new(),
             last_snap_world: None,
@@ -302,6 +306,7 @@ impl Snapper {
             },
             grid_spacing: self.grid_spacing,
             snap_radius_px: self.snap_radius_px,
+            osnap_radius_px: self.osnap_radius_px,
             otrack_enabled: false,
             tracking_points: Vec::new(),
             last_snap_world: None,
@@ -323,7 +328,7 @@ impl Snapper {
             return None;
         }
         let mut best: Option<SnapResult> = None;
-        let mut best_d2 = self.snap_radius_px * self.snap_radius_px;
+        let mut best_d2 = self.osnap_radius_px * self.osnap_radius_px;
 
         // World-space snap radius — derived from the view scale so wires whose
         // entire extent is clearly outside the snap circle can be skipped cheaply
@@ -333,7 +338,7 @@ impl Snapper {
         let world_snap_r = {
             let s = view_proj.col(0).x.abs() * bounds.width * 0.5;
             if s > 1e-6 {
-                self.snap_radius_px / s
+                self.osnap_radius_px / s
             } else {
                 f32::MAX
             }
@@ -514,7 +519,7 @@ impl Snapper {
                         p0 - p1,
                         view_proj,
                         bounds,
-                        self.snap_radius_px,
+                        self.osnap_radius_px,
                     ) {
                         try_pt(ext, SnapType::Extension);
                     }
@@ -529,7 +534,7 @@ impl Snapper {
                         p_last - p_prev,
                         view_proj,
                         bounds,
-                        self.snap_radius_px,
+                        self.osnap_radius_px,
                     ) {
                         try_pt(ext, SnapType::Extension);
                     }