fix(render): correct lineweight display scaling

Remove the global display boost and scale paper-space lineweights with the current sheet zoom across wire, block-wire, and hatch paths.

Fixes #962

src/scene/pipeline/uniforms.rs

@@ -25,8 +25,9 @@ pub struct Uniforms {
     /// zooming inside MSPACE changes one scalar instead of re-tessellating and
     /// re-uploading every dashed wire.
     pub linetype_scale: f32,
-    /// Pads the struct to the uniform alignment required by wgpu.
-    pub _pad: f32,
+    /// Multiplier for screen-space lineweights. Model space keeps `1.0`;
+    /// paper layouts derive it from the current paper zoom.
+    pub lineweight_scale: f32,
 
     // ── Relative-to-eye (double-single) additions ───────────────────────────
     // Appended at the end so existing field offsets are unchanged; shaders that
@@ -116,7 +117,7 @@ impl Uniforms {
             flat_shade: 0.0,
             transparency_enable: 1.0,
             linetype_scale: 1.0,
-            _pad: 0.0,
+            lineweight_scale: 1.0,
             view_rot: camera.view_proj_rte(bounds),
             eye_high,
             _pad_eh: 0.0,

src/scene/view/render.rs

@@ -23,6 +23,7 @@ use crate::scene::{
 };
 
 const DISPLAY_STYLE_CACHE_LIMIT: usize = if cfg!(target_arch = "wasm32") { 4 } else { 24 };
+const MM_TO_PX: f32 = 96.0 / 25.4;
 
 // ── Camera hover state (shader::Program::State) ───────────────────────────
 
@@ -2592,7 +2593,7 @@ impl Scene {
                     wire.fill_tris_low.clear();
                 }
                 if let Some(mm) = style.resolve_lineweight(wire.aci) {
-                    wire.line_weight_px = (mm * (96.0 / 25.4) * 2.0).max(1.0);
+                    wire.line_weight_px = (mm * MM_TO_PX).max(1.0);
                 }
                 for vertex in &mut wire.text_verts {
                     self.apply_display_plot_style(&mut vertex.color, wire.aci, &style);
@@ -2648,7 +2649,7 @@ impl Scene {
                     }
                 }
                 if let Some(mm) = style.resolve_lineweight(hatch.aci) {
-                    hatch.line_weight_px = (mm * (96.0 / 25.4) * 2.0).max(1.0);
+                    hatch.line_weight_px = (mm * MM_TO_PX).max(1.0);
                 }
                 if let crate::scene::model::hatch_model::HatchPattern::Gradient {
                     color2, ..
@@ -2710,7 +2711,7 @@ impl Scene {
             self.apply_display_plot_style(&mut color, wire.aci, &style);
             let line_weight_px = style
                 .resolve_lineweight(wire.aci)
-                .map(|mm| (mm * (96.0 / 25.4) * 2.0).max(1.0))
+                .map(|mm| (mm * MM_TO_PX).max(1.0))
                 .unwrap_or(wire.line_weight_px);
             for (triangle_index, triangle) in wire.fill_tris.chunks_exact(3).enumerate() {
                 let mut boundary = Vec::with_capacity(4);
@@ -2943,15 +2944,8 @@ pub struct InheritStyle {
 
 /// Convert a concrete (already layer-resolved) lineweight to display pixels.
 pub(crate) fn lineweight_to_px(lw: &LineWeight) -> f32 {
-    const MM_TO_PX: f32 = 96.0 / 25.4;
-    // CAD apps display model-space lineweights larger than their true physical
-    // size so the gradations stay legible on screen — at true scale a 0.5 mm
-    // line is ~2 px and is indistinguishable from thinner weights (which all
-    // floor to 1 px). Apply the same legibility boost so weights are pronounced
-    // and tell apart, matching other DWG editors. (#147)
-    const LWT_DISPLAY_BOOST: f32 = 2.0;
     lw.millimeters()
-        .map(|mm| (mm as f32 * MM_TO_PX * LWT_DISPLAY_BOOST).max(1.0))
+        .map(|mm| (mm as f32 * MM_TO_PX).max(1.0))
         .unwrap_or(1.0)
 }
 
@@ -3853,6 +3847,11 @@ impl Scene {
             full_bounds,
             self.document.header.lineweight_display || display_plot_lineweights,
         );
+        if self.current_layout != "Model" {
+            let paper_per_pixel = 2.0 * self.camera.borrow().ortho_size() / canvas.1.max(1.0);
+            let paper_units_per_mm = self.paper_space_unit_factor() as f32;
+            uniforms.lineweight_scale = paper_units_per_mm / paper_per_pixel / MM_TO_PX;
+        }
 
         // Model space: scale linetypes using the current annotation scale so their
         // appearance can match a paper-space viewport at the same drawing scale.

src/shaders/block_wire.wgsl

@@ -5,7 +5,7 @@ struct Uniforms {
     flat_shade: f32,
     transparency_enable: f32,
     linetype_scale: f32,
-    _pad: f32,
+    lineweight_scale: f32,
     view_rot: mat4x4<f32>,
     eye_high: vec3<f32>,
     _pad_eh: f32,
@@ -67,7 +67,7 @@ fn resolve_hw(taper_ratio: f32, world_hw: f32, px_hw: f32) -> f32 {
     if world_hw > 0.0 {
         return max(world_hw / u.world_per_pixel, 0.5);
     }
-    return select(0.5, px_hw, u.lwdisplay_enable > 0.5);
+    return select(0.5, max(px_hw * u.lineweight_scale, 0.5), u.lwdisplay_enable > 0.5);
 }
 
 fn marker_relative(

src/shaders/hatch.wgsl

@@ -14,7 +14,8 @@ struct Uniforms {
     lwdisplay_enable:    f32,
     flat_shade:          f32,
     transparency_enable: f32,
-    _pad:                vec2<f32>,
+    _linetype_scale:     f32,
+    lineweight_scale:    f32,
     // Relative-to-eye (double-single): see wire.wgsl.
     view_rot:            mat4x4<f32>,
     eye_high:            vec3<f32>,
@@ -162,7 +163,11 @@ fn check_family(
         -ddx_xz.x * sin_a + ddx_xz.y * cos_a,
         -ddy_xz.x * sin_a + ddy_xz.y * cos_a,
     )) * 0.5;
-    let width_px = select(1.0, max(fam.line_width, 1.0), u.lwdisplay_enable > 0.5);
+    let width_px = select(
+        1.0,
+        max(fam.line_width * u.lineweight_scale, 1.0),
+        u.lwdisplay_enable > 0.5,
+    );
     let half_line = half_px * width_px;
 
     // World units per screen pixel on each axis — used to light exactly the

src/shaders/hatch_texture.wgsl

@@ -13,7 +13,8 @@ struct Uniforms {
     lwdisplay_enable:    f32,
     flat_shade:          f32,
     transparency_enable: f32,
-    _pad:                vec2<f32>,
+    _linetype_scale:     f32,
+    lineweight_scale:    f32,
     view_rot:            mat4x4<f32>,
     eye_high:            vec3<f32>,
     _pad_eh:             f32,
@@ -146,7 +147,11 @@ fn check_family(
         -ddx_xz.x * sin_a + ddx_xz.y * cos_a,
         -ddy_xz.x * sin_a + ddy_xz.y * cos_a,
     )) * 0.5;
-    let width_px = select(1.0, max(fam.line_width, 1.0), u.lwdisplay_enable > 0.5);
+    let width_px = select(
+        1.0,
+        max(fam.line_width * u.lineweight_scale, 1.0),
+        u.lwdisplay_enable > 0.5,
+    );
     let half_line = half_px * width_px;
 
     let wpx = length(vec2<f32>(ddx_xz.x, ddy_xz.x));

src/shaders/wire.wgsl

@@ -29,7 +29,7 @@ struct Uniforms {
     // every line opaque.
     transparency_enable: f32,
     linetype_scale: f32,
-    _pad: f32,
+    lineweight_scale: f32,
     // ── Relative-to-eye (double-single) ──────────────────────────────────
     // view_rot is the rotation-only view-projection; vertices subtract the eye
     // (eye_high + eye_low, two f32 emulating f64) before transforming, so the
@@ -102,7 +102,7 @@ struct VertexOut {
 fn resolve_hw(taper: f32, world_hw: f32, px_hw: f32) -> f32 {
     if taper > 0.0 { return max(taper / u.world_per_pixel, 0.5); }
     if world_hw > 0.0 { return max(world_hw / u.world_per_pixel, 0.5); }
-    return select(0.5, px_hw, u.lwdisplay_enable > 0.5);
+    return select(0.5, max(px_hw * u.lineweight_scale, 0.5), u.lwdisplay_enable > 0.5);
 }
 
 fn marker_relative(position_high: vec3<f32>, position_low: vec3<f32>, instance: InstanceIn) -> vec3<f32> {

src/shaders/wire_indexed.wgsl

@@ -12,7 +12,7 @@ struct Uniforms {
     flat_shade: f32,
     transparency_enable: f32,
     linetype_scale: f32,
-    _pad: f32,
+    lineweight_scale: f32,
     view_rot:         mat4x4<f32>,
     eye_high:         vec3<f32>,
     _pad_eh:          f32,
@@ -81,7 +81,7 @@ fn resolve_hw(taper_ratio: f32, world_hw: f32, px_hw: f32) -> f32 {
         return max((taper_ratio * world_hw) / u.world_per_pixel, 0.5);
     }
     if world_hw > 0.0 { return max(world_hw / u.world_per_pixel, 0.5); }
-    return select(0.5, px_hw, u.lwdisplay_enable > 0.5);
+    return select(0.5, max(px_hw * u.lineweight_scale, 0.5), u.lwdisplay_enable > 0.5);
 }
 
 fn marker_relative(position_high: vec3<f32>, position_low: vec3<f32>, c: WireConst) -> vec3<f32> {