Merge pull request #2057 from aleksei-suholita/perf/glass-dispersion-narrow-window

M8: glass takes one sample where its colours split under 1/256 px

ROADMAP.md

@@ -2,7 +2,7 @@
 
 **Stage: alpha** · next: beta, ~26 points and ~162–292 h away (one Opus 5.5 agent; ~33–67 h wall-clock with 5 agents)
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-02 · **Change:** minor (glass bends towards its core, and rounded rectangles work it out in closed form; glass's light is a line on its bevel and splay turns the bend towards the centre; glass bends with a thick-lens profile and splits its colours over 8 steps; glass effects take variables and keep their frost within 0–100; web host bridge: `?host=parent` or `data-host="page"` hands a page the app's files, documented in the hosting guide; a connector end moved with Cmd/Ctrl held goes on any part of an object, and stays there as the object moves or resizes; a tap on a plugin panel's button keeps what was typed in its fields; a Dash cap setting (none, round or square) on Dash and Custom strokes, drawn on both ends of every dash; library analytics list how many layers and files use each style and variable; the Controller menu names each button as PlayStation and Switch controllers do; widgets draw lines and SVG pictures (plugin API 6); a connector end dropped along a side of a shape attaches to that side (#1708); regression tests pin a rounded shape's one-sided stroke and SVG ids and font families without XML-forbidden characters (#1351, #1124); a damaged image is refused with a reason instead of showing as an empty box (#1474); an image copied in another app pastes again on the desktop, and in the browser for the first time (#492); SwiftUI and Compose code names a bound variable by its iOS or Android code syntax; the colour picker's Image tab shows a placeholder and Upload from computer, an asset preview, and a file dropped on it replaces the image, keeping the fill mode, crop and position (#1682); the Frame tool's Phone presets have the iPhone 17 family (#1691); Show in folder works in the Flatpak build and selects the file on Linux (#1701); a dashed line starts and ends with a half-length dash, on the canvas and in exports; the Pages, Layers and Assets search fields keep their text in the middle of the field (#1703); a board connector's path can be reshaped by dragging its path handles (#1710); boards have 16 more shapes (arrows, polygons, star, plus and flowchart symbols), in pickers that lay them out in a grid; library analytics count insertions and show insertions and detachments over the past 30 days, 90 days or year; a stroke's Custom style takes a dash pattern of any length as a comma-separated list (#1681); a control request can set its own timeout, up to 10 minutes (`timeoutMs`; `figcraft-cli mcp --attach PORT --timeout SECONDS`) (#1696); gap 6: a widget opens its plugin's panel (plugin API 5), whose callbacks redraw it; the keyboard's Menu key opens the context menu, as Shift+F10 does; an Open link action can open in place of the prototype, with "Open in new tab" off (gap 15); a collection of this file can be extended (Extend collection on its row, `variable.extendCollection`), its extension following its edits at once, and extended collections extend again in the file; the eyedropper with Cmd/Ctrl+Shift makes a colour style or variable of what it picks; a live session's welcome sends the document compressed to clients that read it, about seven times smaller (#1665); a control request that times out says truthfully whether it was dropped or is still running and will take effect, and only screenshots and input blame the window (#1673); a board keeps earlier votes' results, listed newest first in Results and deleted one at a time; the object a stamp will stick to is outlined while the stamp tool is over it or a stamp is dragged over it, and board objects take no drops (gap 24); a server can list the files shared from it now for everyone who reaches it, Home ▸ Online shows them and their links carry no secret (`team_files`, part of #742); team library analytics count detached instances per component and file (gap 10); skipping the Open link notice by command is saved with the preferences at once (gap 15); a selected connector's bar on a board sets its start and end points, solid or dashed, its weight and any colour (#1596); cells copied from a spreadsheet paste onto a board as a table; a long layer name stays on one line in the Export button and the Dev Mode header, ending with an ellipsis, and no longer covers the Design panel (#1650); with hundreds of layers selected, the Design panel and the selection overlays stop going over the whole selection on every frame, so dragging 648 layers averages about 1.1 ms of UI per frame (#1571); plugin panels show pictures: an `image` control, base64 within 256 KB and 4,096 px a side, named by its label (gap 6); `.fig` connector labels without a saved snapshot are kept, centred on their line (gap 1); a drag moving many layers re-runs only what sits around them, not each layer's bindings, sizing, text and instance checks, on every move (#1571); damaged font tracking table offsets are checked instead of wrapping on 32-bit targets, and font indexing makes its existing offset bounds explicit (#1125); BLine truncated
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-06 · **Change:** minor (glass takes one sample instead of its dispersion window where the colours split under 1/256 px; glass bends towards its core, and rounded rectangles work it out in closed form; glass's light is a line on its bevel and splay turns the bend towards the centre; glass bends with a thick-lens profile and splits its colours over 8 steps; glass effects take variables and keep their frost within 0–100; web host bridge: `?host=parent` or `data-host="page"` hands a page the app's files, documented in the hosting guide; a connector end moved with Cmd/Ctrl held goes on any part of an object, and stays there as the object moves or resizes; a tap on a plugin panel's button keeps what was typed in its fields; a Dash cap setting (none, round or square) on Dash and Custom strokes, drawn on both ends of every dash; library analytics list how many layers and files use each style and variable; the Controller menu names each button as PlayStation and Switch controllers do; widgets draw lines and SVG pictures (plugin API 6); a connector end dropped along a side of a shape attaches to that side (#1708); regression tests pin a rounded shape's one-sided stroke and SVG ids and font families without XML-forbidden characters (#1351, #1124); a damaged image is refused with a reason instead of showing as an empty box (#1474); an image copied in another app pastes again on the desktop, and in the browser for the first time (#492); SwiftUI and Compose code names a bound variable by its iOS or Android code syntax; the colour picker's Image tab shows a placeholder and Upload from computer, an asset preview, and a file dropped on it replaces the image, keeping the fill mode, crop and position (#1682); the Frame tool's Phone presets have the iPhone 17 family (#1691); Show in folder works in the Flatpak build and selects the file on Linux (#1701); a dashed line starts and ends with a half-length dash, on the canvas and in exports; the Pages, Layers and Assets search fields keep their text in the middle of the field (#1703); a board connector's path can be reshaped by dragging its path handles (#1710); boards have 16 more shapes (arrows, polygons, star, plus and flowchart symbols), in pickers that lay them out in a grid; library analytics count insertions and show insertions and detachments over the past 30 days, 90 days or year; a stroke's Custom style takes a dash pattern of any length as a comma-separated list (#1681); a control request can set its own timeout, up to 10 minutes (`timeoutMs`; `figcraft-cli mcp --attach PORT --timeout SECONDS`) (#1696); gap 6: a widget opens its plugin's panel (plugin API 5), whose callbacks redraw it; the keyboard's Menu key opens the context menu, as Shift+F10 does; an Open link action can open in place of the prototype, with "Open in new tab" off (gap 15); a collection of this file can be extended (Extend collection on its row, `variable.extendCollection`), its extension following its edits at once, and extended collections extend again in the file; the eyedropper with Cmd/Ctrl+Shift makes a colour style or variable of what it picks; a live session's welcome sends the document compressed to clients that read it, about seven times smaller (#1665); a control request that times out says truthfully whether it was dropped or is still running and will take effect, and only screenshots and input blame the window (#1673); a board keeps earlier votes' results, listed newest first in Results and deleted one at a time; the object a stamp will stick to is outlined while the stamp tool is over it or a stamp is dragged over it, and board objects take no drops (gap 24); a server can list the files shared from it now for everyone who reaches it, Home ▸ Online shows them and their links carry no secret (`team_files`, part of #742); team library analytics count detached instances per component and file (gap 10); skipping the Open link notice by command is saved with the preferences at once (gap 15); a selected connector's bar on a board sets its start and end points, solid or dashed, its weight and any colour (#1596); cells copied from a spreadsheet paste onto a board as a table; a long layer name stays on one line in the Export button and the Dev Mode header, ending with an ellipsis, and no longer covers the Design panel (#1650); with hundreds of layers selected, the Design panel and the selection overlays stop going over the whole selection on every frame, so dragging 648 layers averages about 1.1 ms of UI per frame (#1571); plugin panels show pictures: an `image` control, base64 within 256 KB and 4,096 px a side, named by its label (gap 6); `.fig` connector labels without a saved snapshot are kept, centred on their line (gap 1); a drag moving many layers re-runs only what sits around them, not each layer's bindings, sizing, text and instance checks, on every move (#1571); damaged font tracking table offsets are checked instead of wrLine truncated
 
 FigCraft is a clean-room, open-source, pure-Rust reimplementation of the Figma design workflow,
 native on macOS, Windows, Linux and FreeBSD and in the browser, fully drivable by agents through
@@ -358,6 +358,7 @@ Ranked; detail and milestones in [`docs/roadmap.md`](docs/roadmap.md).
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-11-06 | patch | M8: glass takes one backdrop sample instead of its 18-sample dispersion window where the colours split under 1/256 px (the flat end of the curve, where the move is short), within one level of the window over any backdrop: a large pane renders about 2–5% faster, with the same pixels in the renders compared. Tests: `glass::tests::a_split_too_narrow_to_show_takes_one_sample`. Numbers unchanged |
 | 2026-11-02 | patch | M8, #1885: a glass whose shape is too big to keep whole at the zoom (past `MAX_SHAPE_PX` with its core's margin) bends along its edge normals instead of working out a core, so its fields never cover more pixels than a kept shape's, and the core's feature transform holds 16 bytes a pixel. The edge normals are box-blurred twice again and the bend directions once, as documented. Test: `glass::tests::a_shape_too_big_to_keep_bends_along_its_normals`. Numbers unchanged |
 | 2026-11-02 | minor | M3, #1885: glass bends the backdrop towards its core, the shape shrunk by `depth` and the bevel, as the reference tool's: round a sharp corner the bend turns smoothly instead of meeting along the diagonal, and a part thinner than twice that (a capsule, a letter's stroke) bends across itself towards its own middle (pixels about as deep as any within 2 px). Rectangles, frames, components, instances and sections whose corners aren't smoothed work their glass out in closed form, with nothing to rasterise, transform or keep: a zoom frame draws in 40 ms instead of 54 and a resize frame in 46 instead of 67 (`glass_render_timings`, release, 2×). Other shapes keep their fields, with the bend directions for the last two depths asked for beside them, so dragging the Depth slider works out only those again. Tests: `glass::tests::a_sharp_corner_bends_round_towards_the_core`, `glass::tests::a_thin_part_bends_across_itself`, `glass::tests::neighbouring_strokes_bend_towards_their_own_middles`, `glass::tests::a_rounded_rectangle_in_closed_form_matches_its_distance_transform`, `glass_cut_tests::what_the_shape_depends_on_works_it_out_again_and_nothing_else_does`. Numbers unchanged |
 | 2026-11-02 | minor | M3, #1885: glass's light is a line on its 1-unit bevel added to the backdrop, as the reference tool's: fully where the edge faces the light, none below 0.35 of facing it and 0.6 as much on the opposite side, with a faint gradient across the curve, 5% darker facing the light and lighter opposite (it was a glow mixed towards white, as deep as `splay` made it). `splay` turns the bend from along the edge's normal towards the way away from the layer's centre, as the reference tool's does, and no longer widens the light: files with a splay above 0 look different. The direction to the centre is worked out in the shape's own frame, so cut renders match. Tests: `glass::tests::the_light_lies_on_the_bevel_and_the_gradient_across_the_curve`, `backdrop_tests::splay_turns_the_bend_towards_the_centre`, `glass_cut_tests::the_light_is_a_line_on_the_bevel`. Numbers unchanged |

crates/render/src/glass.rs

@@ -381,15 +381,27 @@ pub(crate) fn bend_at(x: f32, depth: f32, bevel: f32, refraction: f32) -> f32 {
     core + (rim - core) * u
 }
 
+/// Below this split (pixels: the move's length × `k`) the dispersion window takes one sample: its
+/// steps lie within 1/256 px of the moved point, so one sample is within one level (of 255) of the
+/// window even across the hardest edge, from black to white or opaque to clear in a pixel.
+const ONE_SAMPLE_SPLIT_PX: f32 = 1.0 / 256.0;
+
 /// The backdrop seen at pixel coordinates (`x`, `y`) moved by (`dx`, `dy`), its channels split by
 /// `k` (dispersion, 0–1): red moves up to `k` further, blue up to `k` less, each smeared along the
-/// move by a triangular window of [`DISPERSION_STEPS`]. One sample when `k` is too small to show.
+/// move by a triangular window of [`DISPERSION_STEPS`]. One sample when the split is too small to
+/// show: `k` under 0.001, or the channels under [`ONE_SAMPLE_SPLIT_PX`] apart (where the curve
+/// flattens out and the move is short).
 fn dispersed(frosted: &Pixmap, x: f32, y: f32, dx: f32, dy: f32, k: f32) -> [f32; 4] {
-    let at = |s: f32| sample(frosted, x + dx * s, y + dy * s);
-    if k < 0.001 {
-        let s = at(1.0);
+    if k < 0.001 || (dx * dx + dy * dy).sqrt() * k < ONE_SAMPLE_SPLIT_PX {
+        let s = sample(frosted, x + dx, y + dy);
         return [s[0].min(s[3]), s[1].min(s[3]), s[2].min(s[3]), s[3]];
     }
+    dispersion_window(frosted, x, y, dx, dy, k)
+}
+
+/// [`dispersed`]'s triangular window, every step sampled.
+fn dispersion_window(frosted: &Pixmap, x: f32, y: f32, dx: f32, dy: f32, k: f32) -> [f32; 4] {
+    let at = |s: f32| sample(frosted, x + dx * s, y + dy * s);
     let last = (DISPERSION_STEPS - 1) as f32;
     let (mut acc, mut sum) = ([0.0f32; 4], 0.0f32);
     for i in 1..DISPERSION_STEPS - 1 {
@@ -1053,6 +1065,40 @@ mod tests {
         assert_eq!(spread[2], 0.0);
     }
 
+    /// Where the channels split under [`ONE_SAMPLE_SPLIT_PX`], one sample stands in for the window
+    /// within one level, even over the hardest backdrops: 1 px columns of black and white, and of
+    /// white and nothing.
+    #[test]
+    fn a_split_too_narrow_to_show_takes_one_sample() {
+        for clear in [false, true] {
+            let mut p = Pixmap::new(64, 4).unwrap();
+            for (i, px) in p.data_mut().chunks_exact_mut(4).enumerate() {
+                let on = i % 2 == 1;
+                let v = if on { 255 } else { 0 };
+                px.copy_from_slice(&[v, v, v, if clear { v } else { 255 }]);
+            }
+            let mut worst = 0.0f32;
+            for step in 0..400 {
+                let x = 20.0 + step as f32 / 100.0;
+                // Along the columns' rows and across them, and out past the backdrop's last row.
+                for (dx, dy) in [(2.0f32, 0.0f32), (-2.0, 0.0), (1.2, 1.6), (0.0, 2.0), (40.0, 0.0)] {
+                    let k = ONE_SAMPLE_SPLIT_PX * 0.999 / (dx * dx + dy * dy).sqrt();
+                    let one = dispersed(&p, x, 2.0, dx, dy, k);
+                    assert_eq!(one, dispersed(&p, x, 2.0, dx, dy, 0.0), "one sample at {x}");
+                    let window = dispersion_window(&p, x, 2.0, dx, dy, k);
+                    worst = one.iter().zip(window).fold(worst, |m, (a, b)| m.max((a - b).abs()));
+                }
+            }
+            assert!(worst <= 1.0, "clear {clear}: {worst}");
+        }
+        // A wider split still takes the window.
+        let mut p = Pixmap::new(64, 4).unwrap();
+        p.data_mut().chunks_exact_mut(4).step_by(2).for_each(|px| px.copy_from_slice(&[255; 4]));
+        let k = ONE_SAMPLE_SPLIT_PX * 2.0 / 2.0;
+        assert_eq!(dispersed(&p, 20.3, 2.0, 2.0, 0.0, k), dispersion_window(&p, 20.3, 2.0, 2.0, 0.0, k));
+        assert_ne!(dispersed(&p, 20.3, 2.0, 2.0, 0.0, k), dispersed(&p, 20.3, 2.0, 2.0, 0.0, 0.0));
+    }
+
     /// A `w` × `h` coverage with the rectangles `rects` (x, y, width, height) filled.
     fn coverage(w: u32, h: u32, rects: &[(f32, f32, f32, f32)]) -> Pixmap {
         let mut p = Pixmap::new(w, h).unwrap();