Render: level of detail and view clipping for pattern hatches on screen (fixes #544) (#638)

Squash of PR #638 by @STE1200.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/cadcraft-cli/src/main.rs

@@ -7,6 +7,7 @@
 //! cadcraft-cli commands [FILTER]                   command catalog (JSON)
 //! cadcraft-cli mcp [--connect HOST:PORT]           MCP server on stdio (headless or bridged to the app)
 //! cadcraft-cli perf [N]                            timing table on a synthetic N-entity drawing
+//! cadcraft-cli perf FILE                           canvas display-list build of a drawing, zoomed in step by step
 //! cadcraft-cli sample (bracket|floorplan) OUT       write a built-in sample drawing
 //! ```
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
@@ -60,7 +61,7 @@ const USAGE: &str = "usage:
   cadcraft-cli run [FILE | --sample | --metric] [--script TEXT] [--script-file F.scr] [--cmd 'id {json}']... [--save OUT.dxf] [--export OUT.(png|svg|pdf)] [FRAMING]
   cadcraft-cli commands [FILTER]
   cadcraft-cli mcp [--connect HOST:PORT]
-  cadcraft-cli perf [N]
+  cadcraft-cli perf [N | FILE]
   cadcraft-cli sample (bracket|floorplan) OUT.(dxf|dwg|svg|png)
   cadcraft-cli --version
 
@@ -393,11 +394,55 @@ fn synthetic(n: usize, side: f64) -> Result<cadcraft_engine::doc::Drawing, Strin
     Ok(dr)
 }
 
+/// `perf FILE`: the display list built as the canvas builds it (a 1600 x 1000 px view at the
+/// drawing's centre: tolerance, dash level of detail and view window from the zoom band), at
+/// zoom extents and zoomed in 4x at a time, next to the full-detail build plots use.
+fn perf_file(path: &str) -> Result<(), String> {
+    use cadcraft_engine::geom::{Bounds2, Vec2};
+    use cadcraft_engine::render::{Options, build};
+    use std::time::Instant;
+    let ms = |t: Instant| t.elapsed().as_secs_f64() * 1000.0;
+    let mut s = Session::empty();
+    let t = Instant::now();
+    open(&mut s, path)?;
+    let open_ms = ms(t);
+    let st = s.state().map_err(|e| e.to_string())?;
+    let (d, space) = (&st.doc, &st.space);
+    let ext = d.extents(space);
+    let size = ext.width().max(ext.height());
+    if ext.is_empty() || !(size.is_finite() && size > 0.0) {
+        return Err("perf: the drawing is empty".into());
+    }
+    outln!("open {open_ms:.0} ms, {} entities, extents {:.1} x {:.1}", d.entity_count(), ext.width(), ext.height());
+    outln!("{:>8} {:>10} {:>10}", "zoom", "build ms", "prims");
+    let mut finest = Options::default();
+    for k in 0..5 {
+        let zoom = 4f64.powi(k);
+        let h = size / zoom;
+        let pixel = 2f64.powi((h / 1000.0).max(1e-300).log2().floor() as i32);
+        let half = Vec2::new(h * 0.8, h * 0.5);
+        let visible = Bounds2::new(ext.center() - half, ext.center() + half);
+        let screen = Options { tolerance: pixel * 0.5, min_dash: pixel * 2.0, view: Some(visible.expand(h * 0.8)), ..Default::default() };
+        let t = Instant::now();
+        let n = build(d, space, &screen).prims.len();
+        outln!("{:>7}x {:>10.1} {n:>10}", zoom, ms(t));
+        finest = screen;
+    }
+    // Plots: every pattern line, everywhere (last, so its large list doesn't weigh on the above).
+    let t = Instant::now();
+    let n = build(d, space, &Options { min_dash: 0.0, view: None, ..finest }).prims.len();
+    outln!("{:>8} {:>10.1} {n:>10}", "full", ms(t));
+    Ok(())
+}
+
 fn perf(args: &[String]) -> Result<(), String> {
     use cadcraft_engine::doc::Space;
     use cadcraft_engine::geom::{Bounds2, Vec2};
     use cadcraft_engine::{select, snap};
     use std::time::Instant;
+    if let Some(path) = args.first().filter(|a| a.parse::<usize>().is_err()) {
+        return perf_file(path);
+    }
     let n: usize = match args.first() {
         Some(a) => a.parse().map_err(|_| format!("perf: bad entity count {a}"))?,
         None => 200_000,