obsqrbtz/egui_knob
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feat: Add with_sweep_range() method for

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control over knob start position and rotation range. Maintains backward compatibility
This commit is contained in:
sacha-renault
2025-07-05 21:45:57 +02:00
parent 06bca1c13a
commit 9968afbe48
2 changed files with 38 additions and 4 deletions
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6
examples/example_knob.rs
View File

@@ -117,7 +117,8 @@ impl eframe::App for KnobExample {
egui::Color32::from_rgb(100, 255, 100),
)
.with_size(50.0)
.with_label_format(|v| format!("{:.2}%", v)),
.with_label_format(|v| format!("{:.2}%", v))
.with_sweep_range(1. / 8., 0.75),
);
ui.add(
@@ -128,7 +129,8 @@ impl eframe::App for KnobExample {
egui::Color32::from_rgb(50, 50, 220),
egui::Color32::from_rgb(100, 100, 255),
)
.with_size(50.0),
.with_size(50.0)
.with_sweep_range(0., 2.),
);
});
});

36
src/lib.rs
View File

@@ -1,3 +1,5 @@
use core::f32;
use egui::{Align2, Color32, Rect, Response, Sense, Stroke, Ui, Vec2, Widget};
/// Position of the label relative to the knob
@@ -42,6 +44,8 @@ pub struct Knob<'a> {
label_offset: f32,
label_format: Box<dyn Fn(f32) -> String>,
step: Option<f32>,
min_angle: f32,
max_angle: f32,
}
impl<'a> Knob<'a> {
@@ -69,9 +73,37 @@ impl<'a> Knob<'a> {
label_offset: 1.0,
label_format: Box::new(|v| format!("{:.2}", v)),
step: None,
min_angle: -std::f32::consts::PI,
max_angle: std::f32::consts::PI * 0.5,
}
}
/// Sets the angular sweep range of the knob
///
/// This controls where the knob starts and how far it can rotate. By default,
/// knobs start at the bottom-left (135°) and sweep 270° clockwise to bottom-right.
///
/// # Arguments
/// * `start_angle_normalized` - Starting position as fraction of full circle:
/// - `0.0` = bottom (6 o'clock)
/// - `0.25` = left (9 o'clock)
/// - `0.5` = top (12 o'clock)
/// - `0.75` = right (3 o'clock)
/// * `range` - How far the knob can sweep as fraction of full circle:
/// - `0.25` = quarter turn (90°)
/// - `0.5` = half turn (180°)
/// - `0.75` = three-quarter turn (270°)
/// - `1.0` = full turn (360°)
/// - Values > 1.0 create multi-turn knobs
pub fn with_sweep_range(mut self, start_angle_normalized: f32, range: f32) -> Self {
self.min_angle =
start_angle_normalized.rem_euclid(1.) * f32::consts::PI * 2. + f32::consts::PI / 2.;
// A range of 1. represent a full turn
self.max_angle = self.min_angle + range.max(0.) * 2. * f32::consts::PI;
self
}
/// Sets the size of the knob
pub fn with_size(mut self, size: f32) -> Self {
self.size = size;
@@ -210,8 +242,8 @@ impl Widget for Knob<'_> {
let center = knob_rect.center();
let radius = knob_size.x / 2.0;
let angle = (*self.value - self.min) / (self.max - self.min) * std::f32::consts::PI * 1.5
- std::f32::consts::PI;
let angle = self.min_angle
+ (*self.value - self.min) / (self.max - self.min) * (self.max_angle - self.min_angle);
painter.circle_stroke(
center,