Providing more control over hover label in plots

egui/src/widgets/plot/items/bar.rs

@@ -1,5 +1,5 @@
-use crate::emath::NumExt;
 use crate::epaint::{Color32, RectShape, Shape, Stroke};
+use crate::plot::items::num_decimals_with_max_digits;
 
 use super::{add_rulers_and_text, highlighted_color, Orientation, PlotConfig, RectElement};
 use crate::plot::{BarChart, ScreenTransform, Value};
@@ -184,7 +184,7 @@ impl RectElement for Bar {
 
     fn default_values_format(&self, transform: &ScreenTransform) -> String {
         let scale = transform.dvalue_dpos();
-        let y_decimals = ((-scale[1].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
+        let y_decimals = num_decimals_with_max_digits(scale[1], 6);
         format!("\n{:.*}", y_decimals, self.value)
     }
 }

egui/src/widgets/plot/items/box_elem.rs

@@ -1,5 +1,5 @@
-use crate::emath::NumExt;
 use crate::epaint::{Color32, RectShape, Shape, Stroke};
+use crate::plot::items::num_decimals_with_max_digits;
 
 use super::{add_rulers_and_text, highlighted_color, Orientation, PlotConfig, RectElement};
 use crate::plot::{BoxPlot, ScreenTransform, Value};
@@ -268,7 +268,7 @@ impl RectElement for BoxElem {
 
     fn default_values_format(&self, transform: &ScreenTransform) -> String {
         let scale = transform.dvalue_dpos();
-        let y_decimals = ((-scale[1].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
+        let y_decimals = num_decimals_with_max_digits(scale[1], 6);
         format!(
             "\nMax = {max:.decimals$}\
              \nQuartile 3 = {q3:.decimals$}\

egui/src/widgets/plot/items/mod.rs

@@ -7,7 +7,7 @@ use epaint::Mesh;
 
 use crate::*;
 
-use super::{CustomLabelFuncRef, PlotBounds, ScreenTransform};
+use super::{HoverFormatter, HoverLine, PlotBounds, ScreenTransform};
 use rect_elem::*;
 use values::{ClosestElem, PlotGeometry};
 
@@ -26,8 +26,13 @@ const DEFAULT_FILL_ALPHA: f32 = 0.05;
 pub(super) struct PlotConfig<'a> {
     pub ui: &'a Ui,
     pub transform: &'a ScreenTransform,
-    pub show_x: bool,
-    pub show_y: bool,
+    pub hover_config: HoverConfig,
+    pub hover_formatter: &'a HoverFormatter,
+}
+
+pub struct HoverConfig {
+    pub hover_line: HoverLine,
+    pub show_hover_label: bool,
 }
 
 /// Trait shared by things that can be drawn in the plot.
@@ -61,13 +66,7 @@ pub(super) trait PlotItem {
         }
     }
 
-    fn on_hover(
-        &self,
-        elem: ClosestElem,
-        shapes: &mut Vec<Shape>,
-        plot: &PlotConfig<'_>,
-        custom_label_func: &CustomLabelFuncRef,
-    ) {
+    fn on_hover(&self, elem: ClosestElem, shapes: &mut Vec<Shape>, plot: &PlotConfig<'_>) {
         let points = match self.geometry() {
             PlotGeometry::Points(points) => points,
             PlotGeometry::None => {
@@ -89,7 +88,7 @@ pub(super) trait PlotItem {
         let pointer = plot.transform.position_from_value(&value);
         shapes.push(Shape::circle_filled(pointer, 3.0, line_color));
 
-        rulers_at_value(pointer, value, self.name(), plot, shapes, custom_label_func);
+        rulers_at_value(pointer, value, self.name(), plot, shapes);
     }
 }
 
@@ -1375,13 +1374,7 @@ impl PlotItem for BarChart {
         find_closest_rect(&self.bars, point, transform)
     }
 
-    fn on_hover(
-        &self,
-        elem: ClosestElem,
-        shapes: &mut Vec<Shape>,
-        plot: &PlotConfig<'_>,
-        _: &CustomLabelFuncRef,
-    ) {
+    fn on_hover(&self, elem: ClosestElem, shapes: &mut Vec<Shape>, plot: &PlotConfig<'_>) {
         let bar = &self.bars[elem.index];
 
         bar.add_shapes(plot.transform, true, shapes);
@@ -1517,13 +1510,7 @@ impl PlotItem for BoxPlot {
         find_closest_rect(&self.boxes, point, transform)
     }
 
-    fn on_hover(
-        &self,
-        elem: ClosestElem,
-        shapes: &mut Vec<Shape>,
-        plot: &PlotConfig<'_>,
-        _: &CustomLabelFuncRef,
-    ) {
+    fn on_hover(&self, elem: ClosestElem, shapes: &mut Vec<Shape>, plot: &PlotConfig<'_>) {
         let box_plot = &self.boxes[elem.index];
 
         box_plot.add_shapes(plot.transform, true, shapes);
@@ -1570,11 +1557,14 @@ fn add_rulers_and_text(
     text: Option<String>,
     shapes: &mut Vec<Shape>,
 ) {
+    let hover_config = &plot.hover_config;
+
     let orientation = elem.orientation();
-    let show_argument = plot.show_x && orientation == Orientation::Vertical
-        || plot.show_y && orientation == Orientation::Horizontal;
-    let show_values = plot.show_y && orientation == Orientation::Vertical
-        || plot.show_x && orientation == Orientation::Horizontal;
+    let show_argument = hover_config.hover_line.show_x_line()
+        && orientation == Orientation::Vertical
+        || hover_config.hover_line.show_y_line() && orientation == Orientation::Horizontal;
+    let show_values = hover_config.hover_line.show_y_line() && orientation == Orientation::Vertical
+        || hover_config.hover_line.show_x_line() && orientation == Orientation::Horizontal;
 
     let line_color = rulers_color(plot.ui);
 
@@ -1643,52 +1633,32 @@ pub(super) fn rulers_at_value(
     name: &str,
     plot: &PlotConfig<'_>,
     shapes: &mut Vec<Shape>,
-    custom_label_func: &CustomLabelFuncRef,
 ) {
+    let hover_config = &plot.hover_config;
+
     let line_color = rulers_color(plot.ui);
-    if plot.show_x {
+    if hover_config.hover_line.show_x_line() {
         shapes.push(vertical_line(pointer, plot.transform, line_color));
     }
-    if plot.show_y {
+    if hover_config.hover_line.show_y_line() {
         shapes.push(horizontal_line(pointer, plot.transform, line_color));
     }
 
-    let mut prefix = String::new();
-
-    if !name.is_empty() {
-        prefix = format!("{}\n", name);
-    }
-
-    let text = {
-        let scale = plot.transform.dvalue_dpos();
-        let x_decimals = ((-scale[0].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
-        let y_decimals = ((-scale[1].abs().log10()).ceil().at_least(0.0) as usize).at_most(6);
-        if let Some(custom_label) = custom_label_func {
-            custom_label(name, &value)
-        } else if plot.show_x && plot.show_y {
-            format!(
-                "{}x = {:.*}\ny = {:.*}",
-                prefix, x_decimals, value.x, y_decimals, value.y
-            )
-        } else if plot.show_x {
-            format!("{}x = {:.*}", prefix, x_decimals, value.x)
-        } else if plot.show_y {
-            format!("{}y = {:.*}", prefix, y_decimals, value.y)
-        } else {
-            unreachable!()
-        }
-    };
+    if hover_config.show_hover_label {
+        let hover_label_func = plot.hover_formatter;
+        let text = hover_label_func(&plot.hover_config, name, &value);
 
-    let font_id = TextStyle::Body.resolve(plot.ui.style());
+        let font_id = TextStyle::Body.resolve(plot.ui.style());
 
-    shapes.push(Shape::text(
-        &*plot.ui.fonts(),
-        pointer + vec2(3.0, -2.0),
-        Align2::LEFT_BOTTOM,
-        text,
-        font_id,
-        plot.ui.visuals().text_color(),
-    ));
+        shapes.push(Shape::text(
+            &*plot.ui.fonts(),
+            pointer + vec2(3.0, -2.0),
+            Align2::LEFT_BOTTOM,
+            text,
+            font_id,
+            plot.ui.visuals().text_color(),
+        ));
+    }
 }
 
 fn find_closest_rect<'a, T>(
@@ -1710,3 +1680,8 @@ where
         })
         .min_by_key(|e| e.dist_sq.ord())
 }
+
+/// Returns the number of decimals required to show the specified maximum number of digits
+pub(super) fn num_decimals_with_max_digits(value: f64, max_digits: usize) -> usize {
+    max_digits - ((value.abs().log10()).ceil().at_least(0.0) as usize).at_most(max_digits)
+}