initial commit

.gitignore

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+/target

Cargo.toml

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+[package]
+name = "egui_knob"
+version = "0.1.0"
+edition = "2021"
+
+[[bin]]
+name = "demo"
+path = "examples/demo.rs"
+
+[lib]
+name = "egui_knob"
+path = "src/lib.rs"
+
+[dependencies]
+egui = "0.30"
+eframe = { version = "0.30.0", features = ["default_fonts"] }

examples/demo.rs

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+use eframe::egui;
+use egui_knob::Knob;
+
+fn main() -> eframe::Result<()> {
+    eframe::run_native(
+        "Knob Example",
+        eframe::NativeOptions::default(),
+        Box::new(|_cc| Ok(Box::new(KnobExample::default()))),
+    )
+}
+
+struct KnobExample {
+    value: f32,
+}
+
+impl Default for KnobExample {
+    fn default() -> Self {
+        Self { value: 0.5 }
+    }
+}
+
+impl eframe::App for KnobExample {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        egui::CentralPanel::default().show(ctx, |ui| {
+            ui.add(Knob::new(&mut self.value, 0.0, 1.0));
+            ui.label(format!("Value: {:.2}", self.value));
+        });
+    }
+}

src/lib.rs

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+use egui::{Response, Sense, Ui, Vec2, Widget};
+
+pub struct Knob<'a> {
+    value: &'a mut f32,
+    min: f32,
+    max: f32,
+}
+
+impl<'a> Knob<'a> {
+    pub fn new(value: &'a mut f32, min: f32, max: f32) -> Self {
+        Self { value, min, max }
+    }
+}
+
+impl Widget for Knob<'_> {
+    fn ui(self, ui: &mut Ui) -> Response {
+        let desired_size = Vec2::splat(40.0);
+        let (rect, response) = ui.allocate_exact_size(desired_size, Sense::drag());
+
+        if response.dragged() {
+            let delta = response.drag_delta().y;
+            let range = self.max - self.min;
+            let step = range * 0.005;
+            *self.value = (*self.value - delta * step).clamp(self.min, self.max);
+        }
+
+        let painter = ui.painter();
+        let center = rect.center();
+        let radius = rect.width() / 2.0;
+        let angle = (*self.value - self.min) / (self.max - self.min) * std::f32::consts::PI * 1.5
+            - std::f32::consts::PI * 0.75;
+
+        painter.circle_stroke(center, radius, egui::Stroke::new(2.0, ui.visuals().text_color()));
+        let pointer = center + Vec2::angled(angle) * (radius * 0.7);
+        painter.line_segment([center, pointer], egui::Stroke::new(3.0, ui.visuals().text_color()));
+
+        response
+    }
+}