initial commit

src/lib.rs

@@ -0,0 +1,39 @@
+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
+    }
+}