Move all crates into a crates directory (#1940)

crates/egui_demo_lib/src/demo/dancing_strings.rs

@@ -0,0 +1,67 @@
+use egui::{containers::*, *};
+
+#[derive(Default)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "serde", serde(default))]
+pub struct DancingStrings {}
+
+impl super::Demo for DancingStrings {
+    fn name(&self) -> &'static str {
+        "♫ Dancing Strings"
+    }
+
+    fn show(&mut self, ctx: &Context, open: &mut bool) {
+        use super::View as _;
+        Window::new(self.name())
+            .open(open)
+            .default_size(vec2(512.0, 256.0))
+            .vscroll(false)
+            .show(ctx, |ui| self.ui(ui));
+    }
+}
+
+impl super::View for DancingStrings {
+    fn ui(&mut self, ui: &mut Ui) {
+        let color = if ui.visuals().dark_mode {
+            Color32::from_additive_luminance(196)
+        } else {
+            Color32::from_black_alpha(240)
+        };
+
+        Frame::canvas(ui.style()).show(ui, |ui| {
+            ui.ctx().request_repaint();
+            let time = ui.input().time;
+
+            let desired_size = ui.available_width() * vec2(1.0, 0.35);
+            let (_id, rect) = ui.allocate_space(desired_size);
+
+            let to_screen =
+                emath::RectTransform::from_to(Rect::from_x_y_ranges(0.0..=1.0, -1.0..=1.0), rect);
+
+            let mut shapes = vec![];
+
+            for &mode in &[2, 3, 5] {
+                let mode = mode as f64;
+                let n = 120;
+                let speed = 1.5;
+
+                let points: Vec<Pos2> = (0..=n)
+                    .map(|i| {
+                        let t = i as f64 / (n as f64);
+                        let amp = (time * speed * mode).sin() / mode;
+                        let y = amp * (t * std::f64::consts::TAU / 2.0 * mode).sin();
+                        to_screen * pos2(t as f32, y as f32)
+                    })
+                    .collect();
+
+                let thickness = 10.0 / mode as f32;
+                shapes.push(epaint::Shape::line(points, Stroke::new(thickness, color)));
+            }
+
+            ui.painter().extend(shapes);
+        });
+        ui.vertical_centered(|ui| {
+            ui.add(crate::egui_github_link_file!());
+        });
+    }
+}