Break out plotting to own crate egui_plot (#3282)

This replaces `egui::plot` with the new crate `egui_plot`

crates/egui_plot/src/legend.rs

@@ -0,0 +1,258 @@
+use std::{collections::BTreeMap, string::String};
+
+use crate::*;
+
+use super::items::PlotItem;
+
+/// Where to place the plot legend.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Corner {
+    LeftTop,
+    RightTop,
+    LeftBottom,
+    RightBottom,
+}
+
+impl Corner {
+    pub fn all() -> impl Iterator<Item = Corner> {
+        [
+            Corner::LeftTop,
+            Corner::RightTop,
+            Corner::LeftBottom,
+            Corner::RightBottom,
+        ]
+        .iter()
+        .copied()
+    }
+}
+
+/// The configuration for a plot legend.
+#[derive(Clone, PartialEq)]
+pub struct Legend {
+    pub text_style: TextStyle,
+    pub background_alpha: f32,
+    pub position: Corner,
+}
+
+impl Default for Legend {
+    fn default() -> Self {
+        Self {
+            text_style: TextStyle::Body,
+            background_alpha: 0.75,
+            position: Corner::RightTop,
+        }
+    }
+}
+
+impl Legend {
+    /// Which text style to use for the legend. Default: `TextStyle::Body`.
+    pub fn text_style(mut self, style: TextStyle) -> Self {
+        self.text_style = style;
+        self
+    }
+
+    /// The alpha of the legend background. Default: `0.75`.
+    pub fn background_alpha(mut self, alpha: f32) -> Self {
+        self.background_alpha = alpha;
+        self
+    }
+
+    /// In which corner to place the legend. Default: `Corner::RightTop`.
+    pub fn position(mut self, corner: Corner) -> Self {
+        self.position = corner;
+        self
+    }
+}
+
+#[derive(Clone)]
+struct LegendEntry {
+    color: Color32,
+    checked: bool,
+    hovered: bool,
+}
+
+impl LegendEntry {
+    fn new(color: Color32, checked: bool) -> Self {
+        Self {
+            color,
+            checked,
+            hovered: false,
+        }
+    }
+
+    fn ui(&mut self, ui: &mut Ui, text: String, text_style: &TextStyle) -> Response {
+        let Self {
+            color,
+            checked,
+            hovered,
+        } = self;
+
+        let font_id = text_style.resolve(ui.style());
+
+        let galley = ui.fonts(|f| f.layout_delayed_color(text, font_id, f32::INFINITY));
+
+        let icon_size = galley.size().y;
+        let icon_spacing = icon_size / 5.0;
+        let total_extra = vec2(icon_size + icon_spacing, 0.0);
+
+        let desired_size = total_extra + galley.size();
+        let (rect, response) = ui.allocate_exact_size(desired_size, Sense::click());
+
+        response
+            .widget_info(|| WidgetInfo::selected(WidgetType::Checkbox, *checked, galley.text()));
+
+        let visuals = ui.style().interact(&response);
+        let label_on_the_left = ui.layout().horizontal_placement() == Align::RIGHT;
+
+        let icon_position_x = if label_on_the_left {
+            rect.right() - icon_size / 2.0
+        } else {
+            rect.left() + icon_size / 2.0
+        };
+        let icon_position = pos2(icon_position_x, rect.center().y);
+        let icon_rect = Rect::from_center_size(icon_position, vec2(icon_size, icon_size));
+
+        let painter = ui.painter();
+
+        painter.add(epaint::CircleShape {
+            center: icon_rect.center(),
+            radius: icon_size * 0.5,
+            fill: visuals.bg_fill,
+            stroke: visuals.bg_stroke,
+        });
+
+        if *checked {
+            let fill = if *color == Color32::TRANSPARENT {
+                ui.visuals().noninteractive().fg_stroke.color
+            } else {
+                *color
+            };
+            painter.add(epaint::Shape::circle_filled(
+                icon_rect.center(),
+                icon_size * 0.4,
+                fill,
+            ));
+        }
+
+        let text_position_x = if label_on_the_left {
+            rect.right() - icon_size - icon_spacing - galley.size().x
+        } else {
+            rect.left() + icon_size + icon_spacing
+        };
+
+        let text_position = pos2(text_position_x, rect.center().y - 0.5 * galley.size().y);
+        painter.galley_with_color(text_position, galley, visuals.text_color());
+
+        *checked ^= response.clicked_by(PointerButton::Primary);
+        *hovered = response.hovered();
+
+        response
+    }
+}
+
+#[derive(Clone)]
+pub(super) struct LegendWidget {
+    rect: Rect,
+    entries: BTreeMap<String, LegendEntry>,
+    config: Legend,
+}
+
+impl LegendWidget {
+    /// Create a new legend from items, the names of items that are hidden and the style of the
+    /// text. Returns `None` if the legend has no entries.
+    pub(super) fn try_new(
+        rect: Rect,
+        config: Legend,
+        items: &[Box<dyn PlotItem>],
+        hidden_items: &ahash::HashSet<String>,
+    ) -> Option<Self> {
+        // Collect the legend entries. If multiple items have the same name, they share a
+        // checkbox. If their colors don't match, we pick a neutral color for the checkbox.
+        let mut entries: BTreeMap<String, LegendEntry> = BTreeMap::new();
+        items
+            .iter()
+            .filter(|item| !item.name().is_empty())
+            .for_each(|item| {
+                entries
+                    .entry(item.name().to_owned())
+                    .and_modify(|entry| {
+                        if entry.color != item.color() {
+                            // Multiple items with different colors
+                            entry.color = Color32::TRANSPARENT;
+                        }
+                    })
+                    .or_insert_with(|| {
+                        let color = item.color();
+                        let checked = !hidden_items.contains(item.name());
+                        LegendEntry::new(color, checked)
+                    });
+            });
+        (!entries.is_empty()).then_some(Self {
+            rect,
+            entries,
+            config,
+        })
+    }
+
+    // Get the names of the hidden items.
+    pub fn hidden_items(&self) -> ahash::HashSet<String> {
+        self.entries
+            .iter()
+            .filter(|(_, entry)| !entry.checked)
+            .map(|(name, _)| name.clone())
+            .collect()
+    }
+
+    // Get the name of the hovered items.
+    pub fn hovered_entry_name(&self) -> Option<String> {
+        self.entries
+            .iter()
+            .find(|(_, entry)| entry.hovered)
+            .map(|(name, _)| name.to_string())
+    }
+}
+
+impl Widget for &mut LegendWidget {
+    fn ui(self, ui: &mut Ui) -> Response {
+        let LegendWidget {
+            rect,
+            entries,
+            config,
+        } = self;
+
+        let main_dir = match config.position {
+            Corner::LeftTop | Corner::RightTop => Direction::TopDown,
+            Corner::LeftBottom | Corner::RightBottom => Direction::BottomUp,
+        };
+        let cross_align = match config.position {
+            Corner::LeftTop | Corner::LeftBottom => Align::LEFT,
+            Corner::RightTop | Corner::RightBottom => Align::RIGHT,
+        };
+        let layout = Layout::from_main_dir_and_cross_align(main_dir, cross_align);
+        let legend_pad = 4.0;
+        let legend_rect = rect.shrink(legend_pad);
+        let mut legend_ui = ui.child_ui(legend_rect, layout);
+        legend_ui
+            .scope(|ui| {
+                let background_frame = Frame {
+                    inner_margin: vec2(8.0, 4.0).into(),
+                    rounding: ui.style().visuals.window_rounding,
+                    shadow: epaint::Shadow::NONE,
+                    fill: ui.style().visuals.extreme_bg_color,
+                    stroke: ui.style().visuals.window_stroke(),
+                    ..Default::default()
+                }
+                .multiply_with_opacity(config.background_alpha);
+                background_frame
+                    .show(ui, |ui| {
+                        entries
+                            .iter_mut()
+                            .map(|(name, entry)| entry.ui(ui, name.clone(), &config.text_style))
+                            .reduce(|r1, r2| r1.union(r2))
+                            .unwrap()
+                    })
+                    .inner
+            })
+            .inner
+    }
+}