chore: post-merge cleanup for #287/#289

- Reword the two new explanatory comments to describe the behaviour on its
  own instead of citing another product.
- window_to_sheet: drop the unused window_min parameter (the caller already
  derives its coordinate offset from the returned min-corner position) and fix
  the doc comment to match what the function returns.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/update/file.rs

@@ -1072,8 +1072,7 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
                         PlotScale::Fit
                     }
                 };
-                let (scale, ox, oy) =
+                let (scale, ox, oy) = window_to_sheet((win_w, win_h), (sheet_w, sheet_h), scale_sel);
-                    window_to_sheet((win_w, win_h), (x0, y0), (sheet_w, sheet_h), scale_sel);
 
                 let scene = &self.tabs[i].scene;
                 // Cull to the window so a small-area plot doesn't write the whole

src/io/paper_sizes.rs

@@ -63,12 +63,12 @@ pub enum PlotScale {
     Ratio(f64),
 }
 
-/// Map a world-space window onto a sheet. Returns (scale, offset_x, offset_y):
+/// Map a world-space window onto a sheet. Returns (scale, offset_x, offset_y),
-/// world (x, y) -> sheet mm ((x - window_min.0) * scale + offset_x, (y - window_min.1) * scale + offset_y).
+/// where the scaled window is centered on the sheet and (offset_x, offset_y) is
-/// The scaled window is centered on the sheet.
+/// the sheet-mm position of the window's min corner. The caller turns that into
+/// its own coordinate offset.
 pub fn window_to_sheet(
     window_wh: (f64, f64),
-    window_min: (f64, f64),
     sheet_mm: (f64, f64),
     scale: PlotScale,
 ) -> (f64, f64, f64) {
@@ -86,7 +86,6 @@ pub fn window_to_sheet(
     let scaled_h = wh * scale;
     let offset_x = (sheet_mm.0 - scaled_w) / 2.0;
     let offset_y = (sheet_mm.1 - scaled_h) / 2.0;
-    let _ = window_min; // offset already places the window min at (offset_x, offset_y)
     (scale, offset_x, offset_y)
 }
 
@@ -109,7 +108,7 @@ mod tests {
     fn fit_centers_and_scales_within_margin() {
         // 100×100 window onto a 210×297 sheet, Fit. Limiting axis is width:
         // usable = 210/1.05 = 200; scale = 200/100 = 2.0.
-        let (s, ox, oy) = window_to_sheet((100.0, 100.0), (0.0, 0.0), (210.0, 297.0), PlotScale::Fit);
+        let (s, ox, oy) = window_to_sheet((100.0, 100.0), (210.0, 297.0), PlotScale::Fit);
         assert!((s - 2.0).abs() < 1e-9, "scale {s}");
         // Window is 100*2 = 200 wide/tall; centered on 210×297.
         assert!((ox - (210.0 - 200.0) / 2.0).abs() < 1e-9, "ox {ox}");
@@ -117,12 +116,11 @@ mod tests {
     }
 
     #[test]
-    fn ratio_applies_exact_scale_and_offsets_window_min() {
+    fn ratio_applies_exact_scale_and_centers() {
-        // Ratio(0.5): scale is exactly 0.5; a window starting at (10,20)
+        // Ratio(0.5): scale is exactly 0.5; the scaled window is centered and
-        // maps its min corner to the offset so (10,20) -> (ox,oy).
+        // (ox, oy) is the sheet-mm position of its min corner.
-        let (s, ox, oy) = window_to_sheet((100.0, 80.0), (10.0, 20.0), (210.0, 297.0), PlotScale::Ratio(0.5));
+        let (s, ox, oy) = window_to_sheet((100.0, 80.0), (210.0, 297.0), PlotScale::Ratio(0.5));
         assert!((s - 0.5).abs() < 1e-9);
-        // Centered: sheet_center - scaled_window_center, then min maps to offset.
         // scaled window = 50×40; centered box origin = ((210-50)/2,(297-40)/2).
         assert!((ox - (210.0 - 50.0) / 2.0).abs() < 1e-9, "ox {ox}");
         assert!((oy - (297.0 - 40.0) / 2.0).abs() < 1e-9, "oy {oy}");

src/io/pdf_export.rs

@@ -283,10 +283,9 @@ fn build_pdf(
         }
 
         // Line weight: CTB override (in pt) or screen px → points. Divided by
-        // `scale` in both branches so pen widths stay absolute under the
+        // `scale` in both branches so pen widths stay absolute under the scaled
-        // scaled CTM above (AutoCAD keeps lineweights independent of plot
+        // CTM above — lineweights are independent of plot scale, so without this
-        // scale) — without this a Fit plot of a large window renders
+        // a Fit plot of a large window renders near-invisible hairlines.
-        // near-invisible hairlines.
         let lw_pt = lw_override
             .unwrap_or_else(|| (wire.line_weight_px * LW_PX_TO_PT).max(0.1) / scale.max(1e-6));
         if last_lw.map(|l| (l - lw_pt).abs() > 0.01).unwrap_or(true) {

src/scene/camera_ops.rs

@@ -642,9 +642,9 @@ impl Scene {
         // both rejects below: its centroid sits at the base point (inside
         // the consensus cluster), and in a fresh drawing `local_extent_max`
         // is still the 1e9 default, so the far points pass the `lim` filter
-        // too (issue #284). Exclude them up front — matching AutoCAD, where
+        // too (issue #284). Exclude them up front — an infinite construction
-        // infinite lines never contribute to ZOOM Extents — and fall back
+        // line should never contribute to ZOOM Extents — and fall back to their
-        // to their base points if the drawing holds nothing else.
+        // base points if the drawing holds nothing else.
         let mut infinite_base_pts: Vec<glam::Vec3> = Vec::new();
         wires.retain(|w| {
             let is_infinite = Self::handle_from_wire_name(&w.name)