feat(snap): editable Snap X/Y spacing with Equal lock, grid snap locks

Drafting Settings dialog gets text inputs for Snap X/Y spacing plus a working Equal X and Y checkbox (mirrored inputs, Y follows X on apply). Snapper gains fixed snap_spacing_x/y (persisted in UserSettings, default 10) decoupled from the adaptive visible-grid step. Grid snap no longer aperture-gated: with Snap On it rounds every point to the grid, object snaps still override by tier. Adds parse/lock regression tests.

src/app/drafting_settings.rs

@@ -3,10 +3,19 @@ use crate::ui::window::drafting_settings::{DraftingSettingsState, DraftingSettin
 
 impl DraftingSettingsState {
     pub(crate) fn from_app(app: &OpenCADStudio) -> Self {
+        let snap_x = app.snapper.snap_spacing_x;
+        let snap_y = app.snapper.snap_spacing_y;
+        // The dialog has no stored "equal" flag, so infer it: equal when
+        // X and Y match. This keeps the checkbox checked for the common
+        // case (including fresh defaults of 10/10).
+        let snap_equal = (snap_x - snap_y).abs() < 1e-6;
         Self {
             active_tab: DraftingSettingsTab::SnapAndGrid,
             snap_on: app.snapper.grid_snap(),
             grid_on: app.show_grid,
+            snap_x_input: crate::ui::window::drafting_settings::format_snap_spacing(snap_x),
+            snap_y_input: crate::ui::window::drafting_settings::format_snap_spacing(snap_y),
+            snap_equal,
             isometric: app.isometric_drafting,
             iso_plane: app.iso_plane,
             snap_angle_deg: app.snap_angle_deg,
@@ -33,24 +42,42 @@ impl OpenCADStudio {
         }
     }
 
-    pub(super) fn apply_drafting_settings(&mut self) {
-        if let Some(state) = &self.drafting_settings_state {
-            self.show_grid = state.grid_on;
-            self.snapper.grid_snap_on = state.snap_on;
-            self.isometric_drafting = state.isometric;
-            self.iso_plane = state.iso_plane;
-            self.snap_angle_deg = state.snap_angle_deg;
-            self.polar_mode = state.polar_on;
-            self.ortho_mode = state.ortho_on;
-            self.polar_increment_deg = state.polar_increment_deg;
-            self.snapper.snap_enabled = state.osnap_on;
-            self.snapper.otrack_enabled = state.otrack_on;
-            self.snapper.enabled = state.snap_modes.clone();
-            self.dyn_input = state.dyn_input_on;
-            self.quick_properties = state.quick_props_on;
-            self.selection_cycling = state.selection_cycling_on;
-            self.sync_vport_display(self.active_tab);
+    pub(super) fn apply_drafting_settings(&mut self) -> bool {
+        let Some(state) = &self.drafting_settings_state.clone() else {
+            return true;
+        };
+        let x = crate::ui::window::drafting_settings::parse_snap_spacing(&state.snap_x_input);
+        let y = crate::ui::window::drafting_settings::parse_snap_spacing(&state.snap_y_input);
+        let (Some(sx), Some(sy)) = (x, y) else {
+            self.command_line
+                .push_error(crate::t!("Snap X and Y spacings must be positive numbers.").as_ref());
+            return false;
+        };
+        // When locked, Y follows X so the two can never diverge.
+        let sy = if state.snap_equal { sx } else { sy };
+        if let Some(live) = &mut self.drafting_settings_state {
+            if live.snap_equal {
+                live.snap_y_input = live.snap_x_input.clone();
+            }
         }
+        self.show_grid = state.grid_on;
+        self.snapper.grid_snap_on = state.snap_on;
+        self.snapper.snap_spacing_x = sx;
+        self.snapper.snap_spacing_y = sy;
+        self.isometric_drafting = state.isometric;
+        self.iso_plane = state.iso_plane;
+        self.snap_angle_deg = state.snap_angle_deg;
+        self.polar_mode = state.polar_on;
+        self.ortho_mode = state.ortho_on;
+        self.polar_increment_deg = state.polar_increment_deg;
+        self.snapper.snap_enabled = state.osnap_on;
+        self.snapper.otrack_enabled = state.otrack_on;
+        self.snapper.enabled = state.snap_modes.clone();
+        self.dyn_input = state.dyn_input_on;
+        self.quick_properties = state.quick_props_on;
+        self.selection_cycling = state.selection_cycling_on;
+        self.sync_vport_display(self.active_tab);
+        true
     }
 }
 
@@ -64,6 +91,9 @@ mod tests {
             active_tab: DraftingSettingsTab::SnapAndGrid,
             snap_on: false,
             grid_on: true,
+            snap_x_input: "10".to_string(),
+            snap_y_input: "10".to_string(),
+            snap_equal: true,
             isometric: false,
             iso_plane: crate::app::settings::IsoPlane::Left,
             snap_angle_deg: 0.0,
@@ -96,6 +126,9 @@ mod tests {
             active_tab: DraftingSettingsTab::SnapAndGrid,
             snap_on: false,
             grid_on: true,
+            snap_x_input: "10".to_string(),
+            snap_y_input: "10".to_string(),
+            snap_equal: true,
             isometric: false,
             iso_plane: crate::app::settings::IsoPlane::Left,
             snap_angle_deg: 0.0,
@@ -166,5 +199,29 @@ mod tests {
         let mut modded = base.clone();
         modded.selection_cycling_on = true;
         assert!(modded.is_dirty(&base));
+
+        let mut modded = base.clone();
+        modded.snap_x_input = "5".to_string();
+        assert!(modded.is_dirty(&base));
+
+        let mut modded = base.clone();
+        modded.snap_y_input = "5".to_string();
+        assert!(modded.is_dirty(&base));
+
+        let mut modded = base.clone();
+        modded.snap_equal = false;
+        assert!(modded.is_dirty(&base));
+    }
+
+    #[test]
+    fn test_parse_snap_spacing() {
+        use crate::ui::window::drafting_settings::{format_snap_spacing, parse_snap_spacing};
+        assert_eq!(parse_snap_spacing("10"), Some(10.0));
+        assert_eq!(parse_snap_spacing(" 2.5 "), Some(2.5));
+        assert_eq!(parse_snap_spacing("0"), None);
+        assert_eq!(parse_snap_spacing("-1"), None);
+        assert_eq!(parse_snap_spacing("abc"), None);
+        assert_eq!(parse_snap_spacing(""), None);
+        assert_eq!(format_snap_spacing(10.0), "10");
     }
 }

src/app/mod.rs

@@ -2741,6 +2741,9 @@ pub enum Message {
     DraftingSettingsTabChanged(crate::ui::window::drafting_settings::DraftingSettingsTab),
     DraftingSettingsToggleGrid,
     DraftingSettingsToggleSnap,
+    DraftingSettingsSnapXChanged(String),
+    DraftingSettingsSnapYChanged(String),
+    DraftingSettingsToggleEqualSnap,
     DraftingSettingsToggleIsometric,
     DraftingSettingsSetIsoPlane(crate::app::settings::IsoPlane),
     DraftingSettingsResetRotation,

src/app/settings.rs

@@ -434,6 +434,13 @@ pub struct UserSettings {
         deserialize_with = "deserialize_commandline_fade_ms"
     )]
     pub commandline_fade_ms: i32,
+    /// SNAPUNIT X/Y spacing used by grid snap. 10 matches the Drafting
+    /// Settings dialog defaults; older configs without these keys fall
+    /// back via `default_snap_spacing`.
+    #[serde(default = "default_snap_spacing")]
+    pub snap_spacing_x: f32,
+    #[serde(default = "default_snap_spacing")]
+    pub snap_spacing_y: f32,
     /// Most-recently-inserted block names, most recent first, capped to 20.
     /// Used to rank INSERT suggestions without touching the drawing file.
     #[serde(default)]
@@ -455,6 +462,20 @@ fn default_commandline_fade_ms() -> i32 {
     3000
 }
 
+/// Default SNAPUNIT spacing shown in the Drafting Settings dialog.
+fn default_snap_spacing() -> f32 {
+    10.0
+}
+
+/// Clamp a snap spacing to the positive range the dialog accepts.
+pub fn sanitize_snap_spacing(v: f32) -> f32 {
+    if v.is_finite() && v > 0.0 && v <= 1e9 {
+        v
+    } else {
+        10.0
+    }
+}
+
 fn deserialize_commandline_fade_ms<'de, D>(de: D) -> Result<i32, D::Error>
 where
     D: serde::Deserializer<'de>,
@@ -552,6 +573,8 @@ impl Default for UserSettings {
             language: crate::i18n::Language::default(),
             cliprompt_lines: 3,
             commandline_fade_ms: 3000,
+            snap_spacing_x: 10.0,
+            snap_spacing_y: 10.0,
             block_mru: Vec::new(),
             block_freq: std::collections::HashMap::new(),
         }

src/app/update/file.rs

@@ -443,6 +443,8 @@ impl OpenCADStudio {
             commandline_fade_ms: crate::app::settings::clamp_commandline_fade_ms(
                 self.commandline_fade_ms,
             ),
+            snap_spacing_x: self.snapper.snap_spacing_x,
+            snap_spacing_y: self.snapper.snap_spacing_y,
             block_mru: self.block_mru.clone(),
             block_freq: self.block_freq.clone(),
         }
@@ -540,6 +542,10 @@ impl OpenCADStudio {
             crate::app::settings::clamp_commandline_fade_ms(s.commandline_fade_ms);
         self.command_line
             .set_commandline_fade_ms(self.commandline_fade_ms.clamp(0, 60000) as u32);
+        self.snapper.snap_spacing_x =
+            crate::app::settings::sanitize_snap_spacing(s.snap_spacing_x);
+        self.snapper.snap_spacing_y =
+            crate::app::settings::sanitize_snap_spacing(s.snap_spacing_y);
         // Block usage: clone but cap to sane sizes (MRU 20, freq map 200)
         self.block_mru = s.block_mru.iter().take(20).cloned().collect();
         self.block_freq = s

src/app/update/mod.rs

@@ -4484,6 +4484,33 @@ impl OpenCADStudio {
                 }
                 Task::none()
             }
+            Message::DraftingSettingsSnapXChanged(value) => {
+                if let Some(state) = &mut self.drafting_settings_state {
+                    state.snap_x_input = value.clone();
+                    if state.snap_equal {
+                        state.snap_y_input = value;
+                    }
+                }
+                Task::none()
+            }
+            Message::DraftingSettingsSnapYChanged(value) => {
+                if let Some(state) = &mut self.drafting_settings_state {
+                    state.snap_y_input = value.clone();
+                    if state.snap_equal {
+                        state.snap_x_input = value;
+                    }
+                }
+                Task::none()
+            }
+            Message::DraftingSettingsToggleEqualSnap => {
+                if let Some(state) = &mut self.drafting_settings_state {
+                    state.snap_equal = !state.snap_equal;
+                    if state.snap_equal {
+                        state.snap_y_input = state.snap_x_input.clone();
+                    }
+                }
+                Task::none()
+            }
             Message::DraftingSettingsToggleIsometric => {
                 if let Some(state) = &mut self.drafting_settings_state {
                     state.isometric = !state.isometric;
@@ -4574,17 +4601,19 @@ impl OpenCADStudio {
                 Task::none()
             }
             Message::DraftingSettingsApply => {
-                self.apply_drafting_settings();
-                self.drafting_settings_saved = self.drafting_settings_state.clone();
-                self.persist_settings_if_changed();
+                if self.apply_drafting_settings() {
+                    self.drafting_settings_saved = self.drafting_settings_state.clone();
+                    self.persist_settings_if_changed();
+                }
                 Task::none()
             }
             Message::DraftingSettingsOk => {
-                self.apply_drafting_settings();
-                self.drafting_settings_saved = self.drafting_settings_state.clone();
-                self.drafting_settings_close_confirm = false;
-                self.persist_settings_if_changed();
-                self.close_active_modal();
+                if self.apply_drafting_settings() {
+                    self.drafting_settings_saved = self.drafting_settings_state.clone();
+                    self.drafting_settings_close_confirm = false;
+                    self.persist_settings_if_changed();
+                    self.close_active_modal();
+                }
                 Task::none()
             }
             Message::DraftingSettingsClose => {

src/app/update/viewport.rs

@@ -1928,7 +1928,9 @@ impl OpenCADStudio {
                     )
                 }
             };
-            // Sync grid-snap spacing to the adaptive spacing of the visible grid.
+            // Sync the adaptive visible-grid step. It drives display and
+            // snap-aperture tolerances — grid *snap* itself locks to the
+            // fixed SNAPUNIT X/Y spacing from the Drafting Settings dialog.
             self.snapper.grid_spacing = grid_spacing;
             // Cursor and wires are model-space; the snap result is model.
             let snap_cursor = cursor_world;

src/snap.rs

@@ -149,6 +149,11 @@ pub struct Snapper {
     pub grid_snap_on: bool,
     /// World-space grid spacing.
     pub grid_spacing: f32,
+    /// User-configurable snap spacing (SNAPUNIT X/Y). Used for grid-snap
+    /// positions; kept separate from the adaptive `grid_spacing`, which
+    /// tracks the visible grid step and drives tolerances.
+    pub snap_spacing_x: f32,
+    pub snap_spacing_y: f32,
     /// Pixel-radius snap aperture, shared by OSNAP, tracking, polar and
     /// extension so the catch distance is the same everywhere.
     pub osnap_radius_px: f32,
@@ -216,6 +221,8 @@ impl Default for Snapper {
             enabled,
             grid_snap_on: false,
             grid_spacing: 1.0,
+            snap_spacing_x: 10.0,
+            snap_spacing_y: 10.0,
             osnap_radius_px: DEFAULT_OSNAP_RADIUS_PX,
             otrack_enabled: false,
             tracking_points: Vec::new(),
@@ -1012,6 +1019,8 @@ impl Snapper {
             },
             grid_snap_on: false,
             grid_spacing: self.grid_spacing,
+            snap_spacing_x: self.snap_spacing_x,
+            snap_spacing_y: self.snap_spacing_y,
             osnap_radius_px: self.osnap_radius_px,
             otrack_enabled: false,
             tracking_points: Vec::new(),
@@ -1084,9 +1093,16 @@ impl Snapper {
         // Object snaps therefore NEVER catch grid points; only when grid snap is
         // on can a grid corner be picked. It is evaluated first and at the
         // lowest priority, so any object snap inside the aperture overrides it.
+        // Unlike object snap, grid snap LOCKS: like AutoCAD SNAP, every point
+        // rounds to the grid — it is not gated by the aperture. (Gating it
+        // would break as soon as the fixed SNAPUNIT spacing differs from the
+        // adaptive visible-grid step on screen.)
         if self.grid_snap_on {
-            let s = self.grid_spacing as f64;
-            if s.abs() > 1e-9 {
+            let sx = self.snap_spacing_x as f64;
+            let sy = self.snap_spacing_y as f64;
+            // Z has no independent spacing in the dialog; follow X.
+            let sz = sx;
+            if sx.abs() > 1e-9 && sy.abs() > 1e-9 && sz.abs() > 1e-9 {
                 // Round in the UCS grid frame, then map back to world.
                 let (ax, ay, az) = grid_axes;
                 let ax = ax.normalize_or(Vec3::X).as_dvec3();
@@ -1107,13 +1123,16 @@ impl Snapper {
                 } else {
                     (rel.dot(ax), rel.dot(ay))
                 };
-                let ux = (ux / s).round() * s;
-                let uy = (uy / s).round() * s;
-                let uz = (rel.dot(az) / s).round() * s;
+                let ux = (ux / sx).round() * sx;
+                let uy = (uy / sy).round() * sy;
+                let uz = (rel.dot(az) / sz).round() * sz;
                 let gp = origin + ax * ux + ay * uy + az * uz;
                 let screen = world_to_screen(gp, view_rot, eye, bounds);
                 let d2 = dist2(screen, cursor_screen);
-                if d2 < radius2 && in_bounds(screen) {
+                // Lock, don't magnet: any in-pane grid point stands, so the
+                // cursor jumps grid-to-grid even when the SNAPUNIT spacing
+                // is far from the adaptive visible-grid step.
+                if in_bounds(screen) {
                     best = Some(SnapResult {
                         world: gp,
                         screen,
@@ -3815,4 +3834,32 @@ mod ext_tests {
         assert_eq!(res.world, DVec3::ZERO);
     }
 
+    #[test]
+    fn grid_snap_locks_beyond_aperture_with_independent_xy() {
+        let mut s = Snapper::default();
+        s.grid_snap_on = true;
+        s.snap_enabled = false; // grid only
+        s.snap_spacing_x = 1.0;
+        s.snap_spacing_y = 0.5;
+        s.osnap_radius_px = 15.0;
+
+        let view_rot = Mat4::IDENTITY;
+        let eye = DVec3::new(0.0, 0.0, 500.0);
+        let bounds = Rectangle { x: 0.0, y: 0.0, width: 1000.0, height: 1000.0 };
+        let wires: Vec<WireModel> = Vec::new();
+
+        // 500 px per world unit: the cursor sits ~160 px from the nearest
+        // grid corner — far outside the 15 px aperture — yet SNAP must still
+        // lock like AutoCAD instead of magnetizing only when near a point.
+        let cursor_world = DVec3::new(0.32, 0.47, 500.0);
+        let cursor_screen = world_to_screen(cursor_world, view_rot, eye, bounds);
+        let res = s.snap(
+            cursor_world, cursor_screen, &wires,
+            view_rot, eye, bounds, Vec3::ZERO, (Vec3::X, Vec3::Y, Vec3::Z), None,
+        ).expect("grid snap must lock even outside the aperture");
+        assert_eq!(res.snap_type, SnapType::Grid);
+        assert!((res.world.x - 0.0).abs() < 1e-9, "x rounds to 0: {:?}", res.world);
+        assert!((res.world.y - 0.5).abs() < 1e-9, "y rounds to 0.5: {:?}", res.world);
+    }
+
 }

src/ui/window/drafting_settings.rs

@@ -1,7 +1,7 @@
 use crate::app::settings::IsoPlane;
 use crate::app::Message;
 use crate::snap::{SnapType, ALL_SNAP_MODES};
-use iced::widget::{button, checkbox, column, container, row, scrollable, text, Space};
+use iced::widget::{button, checkbox, column, container, row, scrollable, text, text_input, Space};
 use iced::{Background, Border, Element, Fill, Length, Theme};
 use std::borrow::Cow;
 
@@ -28,6 +28,9 @@ pub struct DraftingSettingsState {
     // Snap and Grid
     pub snap_on: bool,
     pub grid_on: bool,
+    pub snap_x_input: String,
+    pub snap_y_input: String,
+    pub snap_equal: bool,
     pub isometric: bool,
     pub iso_plane: IsoPlane,
     pub snap_angle_deg: f32,
@@ -55,6 +58,9 @@ impl DraftingSettingsState {
     pub fn is_dirty(&self, saved: &Self) -> bool {
         self.snap_on != saved.snap_on
             || self.grid_on != saved.grid_on
+            || self.snap_x_input != saved.snap_x_input
+            || self.snap_y_input != saved.snap_y_input
+            || self.snap_equal != saved.snap_equal
             || self.isometric != saved.isometric
             || self.iso_plane != saved.iso_plane
             || (self.snap_angle_deg - saved.snap_angle_deg).abs() > 0.001
@@ -71,6 +77,25 @@ impl DraftingSettingsState {
     }
 }
 
+/// Format a snap spacing value for the dialog's text inputs.
+pub fn format_snap_spacing(v: f32) -> String {
+    if (v - v.round()).abs() < 1e-4 {
+        format!("{}", v.round() as i32)
+    } else {
+        format!("{v}")
+    }
+}
+
+/// Parse a snap spacing input. Spacings must be positive and finite.
+pub fn parse_snap_spacing(s: &str) -> Option<f32> {
+    let v: f32 = s.trim().parse().ok()?;
+    if v.is_finite() && v > 0.0 && v <= 1e9 {
+        Some(v)
+    } else {
+        None
+    }
+}
+
 /// Helper for grouped sub-panels with a light border and header title.
 fn group<'a>(title: impl Into<String>, body: impl Into<Element<'a, Message>>) -> Element<'a, Message> {
     container(
@@ -187,18 +212,28 @@ pub fn view_window<'a>(
             column![
                 row![
                     text(crate::t!("Snap X spacing:")).size(11).width(120),
-                    text("10.00").size(11),
+                    text_input("10", &state.snap_x_input)
+                        .on_input(Message::DraftingSettingsSnapXChanged)
+                        .size(11)
+                        .padding([4, 7])
+                        .width(100),
                 ]
                 .spacing(8)
                 .align_y(iced::Center),
                 row![
                     text(crate::t!("Snap Y spacing:")).size(11).width(120),
-                    text("10.00").size(11),
+                    text_input("10", &state.snap_y_input)
+                        .on_input(Message::DraftingSettingsSnapYChanged)
+                        .size(11)
+                        .padding([4, 7])
+                        .width(100),
                 ]
                 .spacing(8)
                 .align_y(iced::Center),
                 row![
-                    checkbox(true).size(14),
+                    checkbox(state.snap_equal)
+                        .on_toggle(|_| Message::DraftingSettingsToggleEqualSnap)
+                        .size(14),
                     text(crate::t!("Equal X and Y spacing")).size(11),
                 ]
                 .spacing(6)