feat(block-editor): use gray viewport with blue grid

src/app/update/viewport.rs

@@ -3453,7 +3453,10 @@ impl OpenCADStudio {
         vw: f32,
         vh: f32,
     ) -> Option<crate::ui::overlay::UcsIconHit> {
-        if !self.show_ucs_icon || self.tabs[i].active_cmd.is_some() {
+        if !self.show_ucs_icon
+            || self.tabs[i].active_cmd.is_some()
+            || self.tabs[i].active_block_edit_session().is_some()
+        {
             return None;
         }
         let tab = &self.tabs[i];
@@ -4051,7 +4054,10 @@ impl OpenCADStudio {
         // UCS icon: click to select (grips appear), then drag a grip to
         // move/rotate. A click off the icon clears the selection. Works
         // in the corner too (parked icon), not just at the origin.
-        if self.show_ucs_icon && self.tabs[i].active_cmd.is_none() {
+        if self.show_ucs_icon
+            && self.tabs[i].active_cmd.is_none()
+            && self.tabs[i].active_block_edit_session().is_none()
+        {
             if let Some(hit) = self.ucs_icon_hit_info(i, vw, vh) {
                 // Already selected → a press on a grip starts the drag.
                 if self.ucs_icon_selected {

src/app/view/mod.rs

@@ -431,7 +431,12 @@ impl OpenCADStudio {
         mark("viewport_3d");
         let viewport_3d: Element<'_, Message> = if self.layout_settling && !tab.is_start {
             // Omit the shader and drafting overlays for the notice frame.
-            let bg = crosshair_background(tab, is_paper);
+            let in_block_editor = tab.active_block_edit_session().is_some();
+            let bg = if in_block_editor {
+                [0.62, 0.62, 0.62, 1.0]
+            } else {
+                crosshair_background(tab, is_paper)
+            };
             let lum = 0.299 * bg[0] + 0.587 * bg[1] + 0.114 * bg[2];
             let ink = if lum > 0.5 {
                 Color::from_rgba(0.0, 0.0, 0.0, 0.55)
@@ -631,7 +636,12 @@ impl OpenCADStudio {
                 .collect();
             let params_ms = crate::perf::elapsed_ms(t_params);
             let t_bg = crate::perf::enabled().then(iced::time::Instant::now);
-            let bg = crosshair_background(tab, is_paper);
+            let in_block_editor = tab.active_block_edit_session().is_some();
+            let bg = if in_block_editor {
+                [0.62, 0.62, 0.62, 1.0]
+            } else {
+                crosshair_background(tab, is_paper)
+            };
             let bg_ms = crate::perf::elapsed_ms(t_bg);
             if views_ms + params_ms + bg_ms >= 1.0 {
                 crate::perf_record!(
@@ -641,8 +651,9 @@ bg={bg_ms:.1}ms n={view_count}"
             }
             let bg_lum = 0.299 * bg[0] + 0.587 * bg[1] + 0.114 * bg[2];
             let grid_style = crate::ui::overlay::GridStyle {
-                opacity: self.model_space.grid_opacity,
+                opacity: if in_block_editor { 38 } else { self.model_space.grid_opacity },
                 bg_luminance: bg_lum,
+                color: if in_block_editor { [0.27, 0.48, 0.91] } else { [0.80, 0.80, 0.80] },
                 axes: self.grid_axes,
             };
             crate::ui::overlay::grid_overlay(grid, grid_style)
@@ -815,7 +826,9 @@ bg={bg_ms:.1}ms n={view_count}"
             // Rotation-only projection (view_proj_rte): the icon shows axis
             // DIRECTIONS only, so the full view_proj's huge UTM translation would
             // cancel catastrophically in f32 and make the tripod jitter.
-            let ucs_icons: Vec<crate::ui::overlay::UcsIconParams> = if !self.show_ucs_icon {
+            let ucs_icons: Vec<crate::ui::overlay::UcsIconParams> = if !self.show_ucs_icon
+                || tab.active_block_edit_session().is_some()
+            {
                 vec![]
             } else if let Some((vp_cam, full)) = tab.scene.viewport_edit_frame((vw, vh)) {
                 let (_, ux, uy, uz) = tab.ucs_xform().axes();
@@ -1413,7 +1426,9 @@ bg={bg_ms:.1}ms n={view_count}"
             b: desk_bg[2],
             a: desk_bg[3],
         };
-        let bg_color = if is_paper {
+        let bg_color = if tab.active_block_edit_session().is_some() {
+            Color { r: 0.62, g: 0.62, b: 0.62, a: 1.0 }
+        } else if is_paper {
             desk_color
         } else {
             let c = tab.scene.bg_color;

src/ui/overlay.rs

@@ -316,6 +316,7 @@ pub struct CrosshairOptions {
 pub struct GridStyle {
     pub opacity: u8,
     pub bg_luminance: f32,
+    pub color: [f32; 3],
     /// Draw the coloured X/Y axis lines through the grid origin.
     pub axes: bool,
 }
@@ -325,6 +326,7 @@ impl Default for GridStyle {
         Self {
             opacity: 18,
             bg_luminance: 0.15,
+            color: [0.80, 0.80, 0.80],
             axes: true,
         }
     }
@@ -2808,11 +2810,7 @@ fn draw_grid(
     // Major lines stay subtle: ~1.5x the minor alpha with a slightly heavier
     // stroke, matching the reference hierarchy without glaring.
     let major_alpha = (alpha * 1.5).clamp(0.03, 1.0);
-    let (r, g, b) = if style.bg_luminance > 0.5 {
-        (0.10, 0.10, 0.10)
-    } else {
-        (0.80, 0.80, 0.80)
-    };
+    let [r, g, b] = style.color;
     let minor_stroke = canvas::Stroke {
         width: 0.5,
         style: canvas::Style::Solid(Color { r, g, b, a: alpha }),