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Merge pull request #9 from bratorange/logarithmic. Fixes #8

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Logarithmic Knobs
This commit is contained in:
Daniel Dada
2026-01-23 10:55:36 +03:00
committed by GitHub
parent fb3f9d75dc e3a378cc6e
commit a637ff4bca
6 changed files with 61 additions and 27 deletions
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8
README.md
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@@ -18,6 +18,7 @@ A simple, customizable knob widget for egui.
- Configurable sweep range
- Background arc with filled segments
- Adjustable drag sensitivity
- Logarithmic scaling
## Installation
@@ -104,6 +105,13 @@ Knob::new(&mut value, 0.0, 1.0, KnobStyle::Wiper)
.with_label_format(|v| format!("{:.0}%", v * 100.0));
```
#### Logarithmic Knobs
```rust
// Enable logarithmic scaling
Knob::new(&mut value, 0.0, 1.0, KnobStyle::Wiper)
.with_logarithmic_scaling();
```
## Running demo app
```bash

10
examples/example_knob.rs
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@@ -21,6 +21,7 @@ struct KnobDemo {
show_bg_arc: bool,
show_filled: bool,
use_step: bool,
logarithmic_scaling: bool,
knob_color: egui::Color32,
line_color: egui::Color32,
text_color: egui::Color32,
@@ -33,6 +34,7 @@ impl Default for KnobDemo {
show_bg_arc: true,
show_filled: true,
use_step: false,
logarithmic_scaling: false,
knob_color: egui::Color32::DARK_GRAY,
line_color: egui::Color32::LIGHT_BLUE,
text_color: egui::Color32::WHITE,
@@ -51,6 +53,8 @@ impl eframe::App for KnobDemo {
ui.checkbox(&mut self.show_bg_arc, "Background arc");
ui.checkbox(&mut self.show_filled, "Filled segment");
ui.checkbox(&mut self.use_step, "Step (0.02)");
ui.checkbox(&mut self.logarithmic_scaling, "Logarithmic");
});
ui.horizontal(|ui| {
@@ -82,7 +86,7 @@ impl eframe::App for KnobDemo {
.enumerate()
{
ui.vertical(|ui| {
let mut knob = Knob::new(&mut self.values[i], 0.0, 1.0, *config)
let mut knob = Knob::new(&mut self.values[i], 0., 1., *config)
.with_label(*label, LabelPosition::Bottom)
.with_background_arc(self.show_bg_arc)
.with_show_filled_segments(self.show_filled)
@@ -91,6 +95,10 @@ impl eframe::App for KnobDemo {
.with_double_click_reset(0.5)
.with_middle_scroll();
if self.logarithmic_scaling {
knob = knob.with_logarithmic_scaling();
}
if *label == "Wiper, Sweep" {
knob = knob.with_sweep_range(0.25, 0.75).with_size(50.0);
}

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4
src/config.rs
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@@ -18,6 +18,7 @@ pub struct KnobConfig {
pub(crate) max_angle: f32,
pub(crate) reset_value: Option<f32>,
pub(crate) allow_scroll: bool,
pub(crate) logarithmic_scaling: bool,
}
impl KnobConfig {
@@ -39,7 +40,8 @@ impl KnobConfig {
show_background_arc: true,
show_filled_segments: true,
reset_value: None,
allow_scroll:false
allow_scroll:false,
logarithmic_scaling: false,
}
}
}

11
src/render.rs
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@@ -6,27 +6,28 @@ use crate::style::{KnobStyle, LabelPosition};
pub(crate) struct KnobRenderer<'a> {
config: &'a KnobConfig,
value: f32,
raw: f32,
min: f32,
max: f32,
}
impl<'a> KnobRenderer<'a> {
pub fn new(config: &'a KnobConfig, value: f32, min: f32, max: f32) -> Self {
pub fn new(config: &'a KnobConfig, value: f32, raw: f32, min: f32, max: f32) -> Self {
Self {
config,
value,
raw,
min,
max,
}
}
pub fn compute_angle(&self) -> f32 {
if self.min == self.max || self.value.is_nan() {
if self.min == self.max || self.raw.is_nan() {
self.config.min_angle
} else {
self.config.min_angle
+ (self.value - self.min) / (self.max - self.min)
* (self.config.max_angle - self.config.min_angle)
+ self.raw * (self.config.max_angle - self.config.min_angle)
}
}
@@ -99,7 +100,7 @@ impl<'a> KnobRenderer<'a> {
if self.config.show_filled_segments {
let filled_segments = (segments as f32
* ((self.value - self.min) / (self.max - self.min)).clamp(0.0, 1.0))
* self.raw.clamp(0.0, 1.0))
as usize;
if filled_segments > 0 {

53
src/widget.rs
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@@ -1,4 +1,4 @@
use egui::{Color32, Response, Sense, Ui, Widget};
use egui::{remap, Color32, Response, Sense, Ui, Widget};
use crate::config::KnobConfig;
use crate::render::KnobRenderer;
@@ -168,6 +168,10 @@ impl<'a> Knob<'a> {
self.config.allow_scroll = true;
self
}
pub fn with_logarithmic_scaling(mut self) -> Self {
self.config.logarithmic_scaling = true;
self
}
}
impl Widget for Knob<'_> {
@@ -176,8 +180,13 @@ impl Widget for Knob<'_> {
*self.value = self.min;
}
let current_value = *self.value;
let renderer = KnobRenderer::new(&self.config, current_value, self.min, self.max);
let mut raw = if self.config.logarithmic_scaling {
remap(*self.value, self.min..=self.max, 1.0..=10.0).log(10.0)
} else {
remap(*self.value, self.min..=self.max, 0.0..=1.0)
};
let renderer = KnobRenderer::new(&self.config, *self.value, raw, self.min, self.max);
let adjusted_size = renderer.calculate_size(ui);
let (rect, response) = ui.allocate_exact_size(adjusted_size, Sense::click_and_drag());
@@ -185,26 +194,21 @@ impl Widget for Knob<'_> {
let mut response = response;
if response.dragged() {
let delta = response.drag_delta().y;
let range = self.max - self.min;
let step = self.config.step.unwrap_or(range * self.config.drag_sensitivity);
let new_value = (*self.value - delta * step).clamp(self.min, self.max);
let step = self.config.step.unwrap_or(self.config.drag_sensitivity);
raw = (raw - delta * step).clamp(0.0,1.0);
*self.value = if let Some(step) = self.config.step {
let steps = ((new_value - self.min) / step).round();
(self.min + steps * step).clamp(self.min, self.max)
raw = if let Some(step) = self.config.step {
let steps = (raw / step).round();
(steps * step).clamp(0.0, 1.0)
} else {
new_value
raw
};
if self.value.is_nan() {
*self.value = self.min;
*self.value = 0.0;
}
response.mark_changed();
} else if response.double_clicked() {
if let Some(reset_value) = self.config.reset_value {
*self.value = reset_value
}
} else if response.hovered() & self.config.allow_scroll {
if let Some(scoll) = ui.input(|input| {
input.events.iter().find_map(|e| match e {
@@ -212,9 +216,21 @@ impl Widget for Knob<'_> {
_ => None,
})
}) {
*self.value = (*self.value
raw = (raw
+ scoll.y * self.config.step.unwrap_or(self.config.drag_sensitivity))
.clamp(self.min, self.max);
.clamp(0.0, 1.0);
}
}
*self.value = if self.config.logarithmic_scaling {
remap(10f32.powf(raw), 1.0..=10.0, self.min..=self.max)
}else {
remap(raw, 0.0..=1.0, self.min..=self.max)
};
if response.double_clicked() {
if let Some(reset_value) = self.config.reset_value {
*self.value = reset_value
}
}
@@ -222,8 +238,7 @@ impl Widget for Knob<'_> {
let center = knob_rect.center();
let radius = self.config.size / 2.0;
let updated_value = *self.value;
let updated_renderer = KnobRenderer::new(&self.config, updated_value, self.min, self.max);
let updated_renderer = KnobRenderer::new(&self.config, *self.value, raw, self.min, self.max);
updated_renderer.render_knob(ui.painter(), center, radius, response.hovered());
updated_renderer.render_label(ui, rect);