[drag-value] show full precision if needed

egui/src/demos/app.rs

@@ -404,13 +404,13 @@ impl Widgets {
         });
 
         ui.add(Slider::f32(&mut self.slider_value, -10.0..=10.0).text("value"));
-        if ui.add(Button::new("Double it")).clicked {
-            self.slider_value *= 2.0;
-        }
         ui.horizontal(|ui| {
             ui.label("drag this number:");
             ui.add(DragValue::f32(&mut self.slider_value).speed(0.01));
         });
+        if ui.add(Button::new("Assign PI")).clicked {
+            self.slider_value = std::f32::consts::PI;
+        }
 
         ui.horizontal(|ui| {
             ui.add(label!("Single line text input:"));

egui/src/math.rs

@@ -83,3 +83,16 @@ pub fn round_to_precision(value: f32, decimal_places: usize) -> f32 {
         .parse()
         .unwrap_or_else(|_| value)
 }
+
+pub fn format_with_minimum_precision(value: f32, precision: usize) -> String {
+    let text = format!("{:.*}", precision, value);
+    if (text.parse::<f32>().unwrap() - value).abs() <= std::f32::EPSILON {
+        // Enough precision to show the value accurately - good!
+        text
+    } else {
+        // The value has more precision than we expected.
+        // Probably the value was set not by the slider, but from outside.
+        // In any case: show the full value
+        value.to_string()
+    }
+}

egui/src/widgets.rs

@@ -96,7 +96,7 @@ impl Label {
 
     // TODO: this should return a LabelLayout which has a paint method.
     // We can then split Widget::Ui in two: layout + allocating space, and painting.
-    // this allows us to assemble lables, THEN detect interaction, THEN chose color style based on that.
+    // this allows us to assemble labels, THEN detect interaction, THEN chose color style based on that.
     // pub fn layout(self, ui: &mut ui) -> LabelLayout { }
 
     // TODO: a paint method for painting anywhere in a ui.
@@ -570,7 +570,7 @@ impl<'a> Widget for DragValue<'a> {
             .log10()
             .ceil()
             .max(0.0) as usize;
-        let button = Button::new(format!("{:.*}", precision, *value))
+        let button = Button::new(format_with_minimum_precision(*value, precision))
             .sense(Sense::drag())
             .text_style(TextStyle::Monospace);
         let interact = ui.add(button);

egui/src/widgets/slider.rs

@@ -184,7 +184,7 @@ impl<'a> Slider<'a> {
     fn text_ui(&mut self, ui: &mut Ui, x_range: RangeInclusive<f32>) {
         let aim_radius = ui.input().aim_radius();
         let value_text = self.format_value(aim_radius, x_range);
-        let label_text = self.text.as_ref().map(String::as_str).unwrap_or_default();
+        let label_text = self.text.as_deref().unwrap_or_default();
         let text = format!("{}: {}", label_text, value_text);
         let text_color = self.text_color.unwrap_or_else(|| ui.style().text_color);
         ui.add(Label::new(text).multiline(false).text_color(text_color));
@@ -203,16 +203,7 @@ impl<'a> Slider<'a> {
             (-range.log10()).ceil().max(0.0) as usize
         });
 
-        let text = format!("{:.*}", precision, value);
+        format_with_minimum_precision(value, precision)
-        if (text.parse::<f32>().unwrap() - value).abs() <= std::f32::EPSILON {
-            // Enough precision to show the value accurately - good!
-            text
-        } else {
-            // The value has more precision than we expected.
-            // Probably the value was set not by the slider, but from outside.
-            // In any case: show the full value
-            value.to_string()
-        }
     }
 }