Refresh stale depth bounds after geometry edits, allow orbiting through camera poles, and preserve hidden-line occlusion for selected solids.\n\nFixes #957
Model space appearance now follows the active UI theme instead of a
hardcoded dark background. Canvas mode is user-selectable (Match Theme /
Classic CAD Dark / Custom RGB), with matching controls for the paper
sheet and desk surround backgrounds and grid opacity.
Implements industry-standard CAD system variables, all settable via
command name, SETVAR, and the Options dialog:
- COLORTHEME (0/1 dark/light UI scheme, preserves custom palettes)
- COLORSCHEME (interactive named-theme selection)
- BACKGROUND (THEME/CLASSIC/DEFAULT/DESK presets, RGB triplets)
- SELECTIONAREA, SELECTIONAREAOPACITY (translucent marquee fill)
- WINDOWSAREACOLOR/WINDOWAREACOLOR, CROSSINGAREACOLOR (ACI or theme)
- SELECTIONEFFECT, SELECTIONEFFECTCOLOR (GPU highlight pass, driven by
selection_generation invalidation — no retessellation)
- SELECTIONPREVIEW (bit 0 = idle rollover, bit 1 = in-command hover)
- GRIPSIZE, GRIPCOLOR, GRIPHOT, GRIPHOVER (grip overlay styling)
Scene.selection was Rc<RefCell<SelectionState>> (31 fields, ~1.6KB
with poly_points) cloned deep per view_main per pane via
(*sel_ref).clone() at view/mod.rs:760. Replace with
Arc<RefCell<SelectionState>> (Arc::new(RefCell::new(...)) at
scene/mod.rs:1436,1868), SelectionCanvas holds Arc<RefCell> and
selection_overlay takes Arc<RefCell> (overlay.rs:365,415),
view_main does Arc::clone(&tab.scene.selection) (atomic bump)
instead of deep clone. sel_ref stays borrowed for field reads
(vp_size etc.).
Bench (release, n=5000): SelectionState::clone 39-68ns (64pts) /
11-22ns (0pts) vs Arc::clone 7ns — 5-9x on the hot path.
Tests:
- selection_is_arc_not_refcell: asserts type_name contains Arc
- bench_selection_state_clone / bench_selection_arc_clone / bench_selection_state_clone_empty (ignored, release)
ramox81