Merge pull request #6353 from Messhias/feat/g5-brush-lib-game-trails

G5: built-in Game Trails brush library

crates/engine/src/cmd/brushlib.rs

@@ -165,13 +165,13 @@ pub struct BuiltinBrushLibrary {
     make: fn() -> BrushLibrary,
 }
 
-/// The built-in brush libraries, in menu order: original brushes generated in code, one library
-/// per kind of brush.
+/// The built-in brush libraries, in menu order: original brushes generated in code.
 pub const BUILTIN: &[BuiltinBrushLibrary] = &[
     BuiltinBrushLibrary { id: "art-ribbons", name: "Art Ribbons", make: art_ribbons },
     BuiltinBrushLibrary { id: "calligraphic-nibs", name: "Calligraphic Nibs", make: calligraphic_nibs },
     BuiltinBrushLibrary { id: "pattern-borders", name: "Pattern Borders", make: pattern_borders },
     BuiltinBrushLibrary { id: "scatter-shapes", name: "Scatter Shapes", make: scatter_shapes },
+    BuiltinBrushLibrary { id: "game-trails", name: "Game Trails", make: game_trails },
 ];
 
 /// Built-in library `id`, made once.
@@ -378,6 +378,44 @@ fn scatter_shapes() -> BrushLibrary {
     built("Scatter Shapes", doc, brushes)
 }
 
+/// Game Trails: art brushes for motion lines and impact streaks (original game HUD / VFX art).
+fn game_trails() -> BrushLibrary {
+    let speed = {
+        let n = 32;
+        let half = |x: f64| 2.2 * (1.0 - x / 100.0).powf(1.2).max(0.08);
+        let xs = |i: usize| 100.0 * i as f64 / n as f64;
+        let mut pts: Vec<Point> = (0..=n).map(xs).map(|x| Point::new(x, -half(x))).collect();
+        pts.extend((0..n).rev().map(xs).map(|x| Point::new(x, half(x))));
+        PathData::single(SubPath::polyline(&pts, true))
+    };
+    let dash = group(vec![
+        black(shapes::rounded_rectangle(Rect::new(0.0, -1.0, 14.0, 1.0), 1.0)),
+        black(shapes::rounded_rectangle(Rect::new(22.0, -1.0, 36.0, 1.0), 1.0)),
+        black(shapes::rounded_rectangle(Rect::new(44.0, -1.0, 58.0, 1.0), 1.0)),
+        black(shapes::rounded_rectangle(Rect::new(66.0, -1.0, 80.0, 1.0), 1.0)),
+        black(shapes::rounded_rectangle(Rect::new(88.0, -1.0, 100.0, 1.0), 1.0)),
+    ]);
+    let burst = {
+        // A wedge that flares from a tip at x=0 to a wide end at x=100.
+        let tip = Point::new(0.0, 0.0);
+        let top = Point::new(100.0, -6.0);
+        let bot = Point::new(100.0, 6.0);
+        PathData::single(SubPath::polyline(&[tip, top, bot], true))
+    };
+    let zigzag = band(100.0, 1.8, 40, |x| {
+        let t = (x / 12.5).floor();
+        let local = (x / 12.5) - t;
+        if (t as i32) % 2 == 0 { -3.0 + 6.0 * local } else { 3.0 - 6.0 * local }
+    });
+    let brushes = vec![
+        art("Speed Line", black(speed), Colorization::Tints),
+        art("Dash Trail", dash, Colorization::Tints),
+        art("Burst Ray", black(burst), Colorization::Tints),
+        art("Zigzag", black(zigzag), Colorization::Tints),
+    ];
+    built("Game Trails", Document::new(100.0, 100.0), brushes)
+}
+
 // ---------- commands ----------
 
 fn builtin_info(b: &BuiltinBrushLibrary) -> LibraryInfo {

crates/engine/src/tests/brushlib.rs

@@ -104,7 +104,7 @@ fn the_builtin_libraries_are_original_brushes_generated_in_code() {
     let list = run(&mut s, "brush.libraries", json!({}));
     let libs = list["libraries"].as_array().unwrap();
     let ids: Vec<&str> = libs.iter().map(|l| l["id"].as_str().unwrap()).collect();
-    assert_eq!(ids, ["art-ribbons", "calligraphic-nibs", "pattern-borders", "scatter-shapes"]);
+    assert_eq!(ids, ["art-ribbons", "calligraphic-nibs", "pattern-borders", "scatter-shapes", "game-trails"]);
     assert!(libs.iter().all(|l| l["category"] == "builtIn"));
     let lib = run(&mut s, "brush.library", json!({"library": "art ribbons"}));
     assert_eq!(
@@ -112,8 +112,20 @@ fn the_builtin_libraries_are_original_brushes_generated_in_code() {
         ["Notched Ribbon", "Double Line", "Wave", "Teardrop", "Striped Ribbon"]
     );
     assert_eq!(libs[0]["count"].as_u64(), Some(5));
+    let trails = run(&mut s, "brush.library", json!({"library": "game-trails"}));
+    assert_eq!(
+        trails["brushes"].as_array().unwrap().iter().map(|b| b["name"].as_str().unwrap()).collect::<Vec<_>>(),
+        ["Speed Line", "Dash Trail", "Burst Ray", "Zigzag"]
+    );
+    assert_eq!(libs[4]["count"].as_u64(), Some(4));
     // One kind of brush per library, every brush drawing something.
-    for (id, kind) in [("art-ribbons", "art"), ("calligraphic-nibs", "calligraphic"), ("pattern-borders", "pattern"), ("scatter-shapes", "scatter")] {
+    for (id, kind) in [
+        ("art-ribbons", "art"),
+        ("calligraphic-nibs", "calligraphic"),
+        ("pattern-borders", "pattern"),
+        ("scatter-shapes", "scatter"),
+        ("game-trails", "art"),
+    ] {
         let (_, lib) = cmd::brushlib::library(&s, id).unwrap();
         assert!(lib.len() >= 4, "{id}");
         for b in &lib.brushes {