Make egui_plot::PlotMemory public (#3871)

This allows users to e.g. read/write the plot bounds/transform before
and after showing a `Plot`.

crates/egui_demo_lib/src/demo/plot_demo.rs

@@ -769,7 +769,20 @@ struct InteractionDemo {}
 impl InteractionDemo {
     #[allow(clippy::unused_self)]
     fn ui(&mut self, ui: &mut Ui) -> Response {
-        let plot = Plot::new("interaction_demo").height(300.0);
+        let id = ui.make_persistent_id("interaction_demo");
+
+        // This demonstrates how to read info about the plot _before_ showing it:
+        let plot_memory = egui_plot::PlotMemory::load(ui.ctx(), id);
+        if let Some(plot_memory) = plot_memory {
+            let bounds = plot_memory.bounds();
+            ui.label(format!(
+                "plot bounds: min: {:.02?}, max: {:.02?}",
+                bounds.min(),
+                bounds.max()
+            ));
+        }
+
+        let plot = Plot::new("interaction_demo").id(id).height(300.0);
 
         let PlotResponse {
             response,

crates/egui_plot/src/legend.rs

@@ -226,7 +226,7 @@ impl LegendWidget {
     }
 
     // Get the name of the hovered items.
-    pub fn hovered_entry_name(&self) -> Option<String> {
+    pub fn hovered_item_name(&self) -> Option<String> {
         self.entries
             .iter()
             .find(|(_, entry)| entry.hovered)

crates/egui_plot/src/lib.rs

@@ -1,9 +1,17 @@
 //! Simple plotting library for [`egui`](https://github.com/emilk/egui).
 //!
+//! Check out [`Plot`] for how to get started.
+//!
 //! ## Feature flags
 #![cfg_attr(feature = "document-features", doc = document_features::document_features!())]
 //!
 
+mod axis;
+mod items;
+mod legend;
+mod memory;
+mod transform;
+
 use std::{ops::RangeInclusive, sync::Arc};
 
 use egui::ahash::HashMap;
@@ -26,11 +34,7 @@ pub use transform::{PlotBounds, PlotTransform};
 use items::{horizontal_line, rulers_color, vertical_line};
 
 pub use axis::{Axis, AxisHints, HPlacement, Placement, VPlacement};
-
-mod axis;
-mod items;
-mod legend;
-mod transform;
+pub use memory::PlotMemory;
 
 type LabelFormatterFn = dyn Fn(&str, &PlotPoint) -> String;
 type LabelFormatter = Option<Box<LabelFormatterFn>>;
@@ -77,44 +81,6 @@ impl Default for CoordinatesFormatter {
 
 const MIN_LINE_SPACING_IN_POINTS: f64 = 6.0; // TODO(emilk): large enough for a wide label
 
-/// Information about the plot that has to persist between frames.
-#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
-#[derive(Clone)]
-struct PlotMemory {
-    /// Indicates if the plot uses automatic bounds. This is disengaged whenever the user modifies
-    /// the bounds, for example by moving or zooming.
-    auto_bounds: Vec2b,
-
-    hovered_entry: Option<String>,
-    hidden_items: ahash::HashSet<String>,
-    last_plot_transform: PlotTransform,
-
-    /// Allows to remember the first click position when performing a boxed zoom
-    last_click_pos_for_zoom: Option<Pos2>,
-}
-
-#[cfg(feature = "serde")]
-impl PlotMemory {
-    pub fn load(ctx: &Context, id: Id) -> Option<Self> {
-        ctx.data_mut(|d| d.get_persisted(id))
-    }
-
-    pub fn store(self, ctx: &Context, id: Id) {
-        ctx.data_mut(|d| d.insert_persisted(id, self));
-    }
-}
-
-#[cfg(not(feature = "serde"))]
-impl PlotMemory {
-    pub fn load(ctx: &Context, id: Id) -> Option<Self> {
-        ctx.data_mut(|d| d.get_temp(id))
-    }
-
-    pub fn store(self, ctx: &Context, id: Id) {
-        ctx.data_mut(|d| d.insert_temp(id, self));
-    }
-}
-
 // ----------------------------------------------------------------------------
 
 /// Indicates a vertical or horizontal cursor line in plot coordinates.
@@ -166,6 +132,7 @@ pub struct PlotResponse<R> {
 /// ```
 /// # egui::__run_test_ui(|ui| {
 /// use egui_plot::{Line, Plot, PlotPoints};
+///
 /// let sin: PlotPoints = (0..1000).map(|i| {
 ///     let x = i as f64 * 0.01;
 ///     [x, x.sin()]
@@ -176,6 +143,7 @@ pub struct PlotResponse<R> {
 /// ```
 pub struct Plot {
     id_source: Id,
+    id: Option<Id>,
 
     center_axis: Vec2b,
     allow_zoom: Vec2b,
@@ -218,6 +186,7 @@ impl Plot {
     pub fn new(id_source: impl std::hash::Hash) -> Self {
         Self {
             id_source: Id::new(id_source),
+            id: None,
 
             center_axis: false.into(),
             allow_zoom: true.into(),
@@ -256,6 +225,17 @@ impl Plot {
         }
     }
 
+    /// Set an explicit (global) id for the plot.
+    ///
+    /// This will override the id set by [`Self::new`].
+    ///
+    /// This is the same `Id` that can be used for [`PlotMemory::load`].
+    #[inline]
+    pub fn id(mut self, id: Id) -> Self {
+        self.id = Some(id);
+        self
+    }
+
     /// width / height ratio of the data.
     /// For instance, it can be useful to set this to `1.0` for when the two axes show the same
     /// unit.
@@ -716,6 +696,7 @@ impl Plot {
     ) -> PlotResponse<R> {
         let Self {
             id_source,
+            id,
             center_axis,
             allow_zoom,
             allow_drag,
@@ -850,7 +831,7 @@ impl Plot {
         let rect = plot_rect;
 
         // Load or initialize the memory.
-        let plot_id = ui.make_persistent_id(id_source);
+        let plot_id = id.unwrap_or_else(|| ui.make_persistent_id(id_source));
         ui.ctx().check_for_id_clash(plot_id, rect, "Plot");
         let memory = if reset {
             if let Some((name, _)) = linked_axes.as_ref() {
@@ -865,22 +846,17 @@ impl Plot {
         }
         .unwrap_or_else(|| PlotMemory {
             auto_bounds: default_auto_bounds,
-            hovered_entry: None,
+            hovered_item: None,
             hidden_items: Default::default(),
-            last_plot_transform: PlotTransform::new(
-                rect,
-                min_auto_bounds,
-                center_axis.x,
-                center_axis.y,
-            ),
+            transform: PlotTransform::new(rect, min_auto_bounds, center_axis.x, center_axis.y),
             last_click_pos_for_zoom: None,
         });
 
         let PlotMemory {
             mut auto_bounds,
-            mut hovered_entry,
+            mut hovered_item,
             mut hidden_items,
-            last_plot_transform,
+            transform: last_plot_transform,
             mut last_click_pos_for_zoom,
         } = memory;
 
@@ -919,14 +895,14 @@ impl Plot {
         let legend = legend_config
             .and_then(|config| LegendWidget::try_new(rect, config, &items, &hidden_items));
         // Don't show hover cursor when hovering over legend.
-        if hovered_entry.is_some() {
+        if hovered_item.is_some() {
             show_x = false;
             show_y = false;
         }
         // Remove the deselected items.
         items.retain(|item| !hidden_items.contains(item.name()));
         // Highlight the hovered items.
-        if let Some(hovered_name) = &hovered_entry {
+        if let Some(hovered_name) = &hovered_item {
             items
                 .iter_mut()
                 .filter(|entry| entry.name() == hovered_name)
@@ -1211,7 +1187,7 @@ impl Plot {
         if let Some(mut legend) = legend {
             ui.add(&mut legend);
             hidden_items = legend.hidden_items();
-            hovered_entry = legend.hovered_entry_name();
+            hovered_item = legend.hovered_item_name();
         }
 
         if let Some((id, _)) = linked_cursors.as_ref() {
@@ -1242,9 +1218,9 @@ impl Plot {
 
         let memory = PlotMemory {
             auto_bounds,
-            hovered_entry,
+            hovered_item,
             hidden_items,
-            last_plot_transform: transform,
+            transform,
             last_click_pos_for_zoom,
         };
         memory.store(ui.ctx(), plot_id);

crates/egui_plot/src/memory.rs

@@ -1,33 +1,72 @@
-use epaint::Pos2;
+use egui::{ahash, Context, Id, Pos2, Vec2b};
 
-use crate::{Context, Id};
-
-use super::{transform::ScreenTransform, AxisBools};
+use crate::{PlotBounds, PlotTransform};
 
 /// Information about the plot that has to persist between frames.
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[derive(Clone)]
-pub(super) struct PlotMemory {
-    /// Indicates if the user has modified the bounds, for example by moving or zooming,
-    /// or if the bounds should be calculated based by included point or auto bounds.
-    pub(super) bounds_modified: AxisBools,
+pub struct PlotMemory {
+    /// Indicates if the plot uses automatic bounds.
+    ///
+    /// This is set to `false` whenever the user modifies
+    /// the bounds, for example by moving or zooming.
+    pub auto_bounds: Vec2b,
 
-    pub(super) hovered_entry: Option<String>,
+    /// Which item is hovered?
+    pub hovered_item: Option<String>,
 
-    pub(super) hidden_items: ahash::HashSet<String>,
+    /// Which items _not_ to show?
+    pub hidden_items: ahash::HashSet<String>,
 
-    pub(super) last_screen_transform: ScreenTransform,
+    /// The transform from last frame.
+    pub(crate) transform: PlotTransform,
 
     /// Allows to remember the first click position when performing a boxed zoom
-    pub(super) last_click_pos_for_zoom: Option<Pos2>,
+    pub(crate) last_click_pos_for_zoom: Option<Pos2>,
+}
+
+impl PlotMemory {
+    #[inline]
+    pub fn transform(&self) -> PlotTransform {
+        self.transform
+    }
+
+    #[inline]
+    pub fn set_transform(&mut self, t: PlotTransform) {
+        self.transform = t;
+    }
+
+    /// Plot-space bounds.
+    #[inline]
+    pub fn bounds(&self) -> &PlotBounds {
+        self.transform.bounds()
+    }
+
+    /// Plot-space bounds.
+    #[inline]
+    pub fn set_bounds(&mut self, bounds: PlotBounds) {
+        self.transform.set_bounds(bounds);
+    }
+}
+
+#[cfg(feature = "serde")]
+impl PlotMemory {
+    pub fn load(ctx: &Context, id: Id) -> Option<Self> {
+        ctx.data_mut(|d| d.get_persisted(id))
+    }
+
+    pub fn store(self, ctx: &Context, id: Id) {
+        ctx.data_mut(|d| d.insert_persisted(id, self));
+    }
 }
 
+#[cfg(not(feature = "serde"))]
 impl PlotMemory {
     pub fn load(ctx: &Context, id: Id) -> Option<Self> {
-        ctx.data().get_persisted(id)
+        ctx.data_mut(|d| d.get_temp(id))
     }
 
     pub fn store(self, ctx: &Context, id: Id) {
-        ctx.data().insert_persisted(id, self);
+        ctx.data_mut(|d| d.insert_temp(id, self));
     }
 }