feat: editable grid spacing and major grid lines in Drafting Settings

The Snap and Grid tab showed static grid values with dead checkboxes, and every grid line stroked identically.

Grid X/Y spacing and Major-line-every are now editable inputs (validated 2-100 for majors, dirty-tracked, applied with an error message on bad input); Adaptive-grid and Display-beyond-Limits checkboxes are wired to live state. Every Nth line partitions into major_segments and strokes subtly brighter (1.5x alpha, 0.75px) for the reference hierarchy. GRIDMAJOR state persists to UserSettings. Covers partition, invalidation, and parse tests.

src/app/drafting_settings.rs

@@ -16,6 +16,15 @@ impl DraftingSettingsState {
             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,
+            grid_x_input: crate::ui::window::drafting_settings::format_snap_spacing(
+                app.grid_spacing_x,
+            ),
+            grid_y_input: crate::ui::window::drafting_settings::format_snap_spacing(
+                app.grid_spacing_y,
+            ),
+            grid_major_input: format!("{}", app.grid_major_every),
+            grid_adaptive: app.grid_adaptive,
+            grid_beyond_limits: app.grid_beyond_limits,
             isometric: app.isometric_drafting,
             iso_plane: app.iso_plane,
             snap_angle_deg: app.snap_angle_deg,
@@ -61,7 +70,22 @@ impl OpenCADStudio {
                 live.snap_y_input = live.snap_x_input.clone();
             }
         }
+        let gx = crate::ui::window::drafting_settings::parse_snap_spacing(&state.grid_x_input);
+        let gy = crate::ui::window::drafting_settings::parse_snap_spacing(&state.grid_y_input);
+        let gm = crate::ui::window::drafting_settings::parse_grid_major(&state.grid_major_input);
+        let (Some(gx), Some(gy), Some(gm)) = (gx, gy, gm) else {
+            self.command_line.push_error(
+                crate::t!("Grid X/Y spacings must be positive numbers and Major every 2-100.")
+                    .as_ref(),
+            );
+            return false;
+        };
         self.show_grid = state.grid_on;
+        self.grid_spacing_x = gx;
+        self.grid_spacing_y = gy;
+        self.grid_major_every = gm;
+        self.grid_adaptive = state.grid_adaptive;
+        self.grid_beyond_limits = state.grid_beyond_limits;
         self.snapper.grid_snap_on = state.snap_on;
         self.snapper.snap_spacing_x = sx;
         self.snapper.snap_spacing_y = sy;
@@ -97,6 +121,11 @@ mod tests {
             snap_x_input: "10".to_string(),
             snap_y_input: "10".to_string(),
             snap_equal: true,
+            grid_x_input: "10".to_string(),
+            grid_y_input: "10".to_string(),
+            grid_major_input: "5".to_string(),
+            grid_adaptive: true,
+            grid_beyond_limits: true,
             isometric: false,
             iso_plane: crate::app::settings::IsoPlane::Left,
             snap_angle_deg: 0.0,
@@ -133,6 +162,11 @@ mod tests {
             snap_x_input: "10".to_string(),
             snap_y_input: "10".to_string(),
             snap_equal: true,
+            grid_x_input: "10".to_string(),
+            grid_y_input: "10".to_string(),
+            grid_major_input: "5".to_string(),
+            grid_adaptive: true,
+            grid_beyond_limits: true,
             isometric: false,
             iso_plane: crate::app::settings::IsoPlane::Left,
             snap_angle_deg: 0.0,
@@ -220,11 +254,33 @@ mod tests {
         let mut modded = base.clone();
         modded.snap_equal = false;
         assert!(modded.is_dirty(&base));
+
+        let mut modded = base.clone();
+        modded.grid_x_input = "5".to_string();
+        assert!(modded.is_dirty(&base));
+
+        let mut modded = base.clone();
+        modded.grid_y_input = "5".to_string();
+        assert!(modded.is_dirty(&base));
+
+        let mut modded = base.clone();
+        modded.grid_major_input = "10".to_string();
+        assert!(modded.is_dirty(&base));
+
+        let mut modded = base.clone();
+        modded.grid_adaptive = false;
+        assert!(modded.is_dirty(&base));
+
+        let mut modded = base.clone();
+        modded.grid_beyond_limits = false;
+        assert!(modded.is_dirty(&base));
     }
 
     #[test]
     fn test_parse_snap_spacing() {
-        use crate::ui::window::drafting_settings::{format_snap_spacing, parse_snap_spacing};
+        use crate::ui::window::drafting_settings::{
+            format_snap_spacing, parse_grid_major, 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);
@@ -232,5 +288,9 @@ mod tests {
         assert_eq!(parse_snap_spacing("abc"), None);
         assert_eq!(parse_snap_spacing(""), None);
         assert_eq!(format_snap_spacing(10.0), "10");
+        assert_eq!(parse_grid_major("5"), Some(5));
+        assert_eq!(parse_grid_major("1"), None);
+        assert_eq!(parse_grid_major("101"), None);
+        assert_eq!(parse_grid_major("abc"), None);
     }
 }

src/app/mod.rs

@@ -545,6 +545,8 @@ pub(super) struct OpenCADStudio {
     /// GRIDUNIT X/Y display spacing backing the DSettings grid-resize inputs.
     pub grid_spacing_x: f32,
     pub grid_spacing_y: f32,
+    /// GRIDMAJOR: every Nth line draws as a brighter major line.
+    pub grid_major_every: u32,
     /// Adaptive grid: scale GRIDUNIT up by 5x steps to stay readable.
     pub grid_adaptive: bool,
     /// Display the grid beyond LIMITS (infinite) instead of clipping to them.
@@ -2767,6 +2769,11 @@ pub enum Message {
     DraftingSettingsToggleSnap,
     DraftingSettingsSnapXChanged(String),
     DraftingSettingsSnapYChanged(String),
+    DraftingSettingsGridXChanged(String),
+    DraftingSettingsGridYChanged(String),
+    DraftingSettingsGridMajorChanged(String),
+    DraftingSettingsToggleAdaptiveGrid,
+    DraftingSettingsToggleBeyondLimits,
     DraftingSettingsToggleEqualSnap,
     DraftingSettingsToggleIsometric,
     DraftingSettingsSetIsoPlane(crate::app::settings::IsoPlane),
@@ -3815,6 +3822,7 @@ impl OpenCADStudio {
             show_grid: false,
             grid_spacing_x: 10.0,
             grid_spacing_y: 10.0,
+            grid_major_every: 5,
             grid_adaptive: true,
             grid_beyond_limits: true,
             dyn_input: true,

src/app/settings.rs

@@ -464,6 +464,9 @@ pub struct UserSettings {
     pub grid_spacing_x: f32,
     #[serde(default = "default_snap_spacing")]
     pub grid_spacing_y: f32,
+    /// GRIDMAJOR: every Nth grid line is a brighter major line.
+    #[serde(default = "default_grid_major")]
+    pub grid_major_every: u32,
     /// Adaptive grid scaling (default on).
     #[serde(default = "default_true")]
     pub grid_adaptive: bool,
@@ -496,10 +499,19 @@ fn default_snap_spacing() -> f32 {
     10.0
 }
 
+fn default_grid_major() -> u32 {
+    5
+}
+
 fn default_true() -> bool {
     true
 }
 
+/// Clamp a major-line interval to the range the dialog accepts.
+pub fn sanitize_grid_major(v: u32) -> u32 {
+    v.clamp(2, 100)
+}
+
 /// 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 {
@@ -616,6 +628,7 @@ impl Default for UserSettings {
             snap_spacing_y: 10.0,
             grid_spacing_x: 10.0,
             grid_spacing_y: 10.0,
+            grid_major_every: 5,
             grid_adaptive: true,
             grid_beyond_limits: true,
             block_mru: Vec::new(),

src/app/update/file.rs

@@ -533,6 +533,7 @@ impl OpenCADStudio {
             snap_spacing_y: self.snapper.snap_spacing_y,
             grid_spacing_x: self.grid_spacing_x,
             grid_spacing_y: self.grid_spacing_y,
+            grid_major_every: self.grid_major_every,
             grid_adaptive: self.grid_adaptive,
             grid_beyond_limits: self.grid_beyond_limits,
             block_mru: self.block_mru.clone(),
@@ -641,6 +642,7 @@ impl OpenCADStudio {
             crate::app::settings::sanitize_snap_spacing(s.snap_spacing_y);
         self.grid_spacing_x = crate::app::settings::sanitize_snap_spacing(s.grid_spacing_x);
         self.grid_spacing_y = crate::app::settings::sanitize_snap_spacing(s.grid_spacing_y);
+        self.grid_major_every = crate::app::settings::sanitize_grid_major(s.grid_major_every);
         self.grid_adaptive = s.grid_adaptive;
         self.grid_beyond_limits = s.grid_beyond_limits;
         // Block usage: clone but cap to sane sizes (MRU 20, freq map 200)

src/app/update/mod.rs

@@ -4596,6 +4596,36 @@ impl OpenCADStudio {
                 }
                 Task::none()
             }
+            Message::DraftingSettingsGridXChanged(value) => {
+                if let Some(state) = &mut self.drafting_settings_state {
+                    state.grid_x_input = value;
+                }
+                Task::none()
+            }
+            Message::DraftingSettingsGridYChanged(value) => {
+                if let Some(state) = &mut self.drafting_settings_state {
+                    state.grid_y_input = value;
+                }
+                Task::none()
+            }
+            Message::DraftingSettingsGridMajorChanged(value) => {
+                if let Some(state) = &mut self.drafting_settings_state {
+                    state.grid_major_input = value;
+                }
+                Task::none()
+            }
+            Message::DraftingSettingsToggleAdaptiveGrid => {
+                if let Some(state) = &mut self.drafting_settings_state {
+                    state.grid_adaptive = !state.grid_adaptive;
+                }
+                Task::none()
+            }
+            Message::DraftingSettingsToggleBeyondLimits => {
+                if let Some(state) = &mut self.drafting_settings_state {
+                    state.grid_beyond_limits = !state.grid_beyond_limits;
+                }
+                Task::none()
+            }
             Message::DraftingSettingsToggleEqualSnap => {
                 if let Some(state) = &mut self.drafting_settings_state {
                     state.snap_equal = !state.snap_equal;

src/app/view/mod.rs

@@ -465,6 +465,7 @@ impl OpenCADStudio {
                         bounds,
                         step_x,
                         step_y,
+                        major_every: self.grid_major_every,
                         origin,
                         axes,
                         limits,