Plot widget - allow disabling zoom and drag for x and y separately (#2901)

* Set whether zooming allowed for x and y separately

* Set whether dragging allowed for x and y separately

* Add disclaimers about interaction with data_aspect

* Show zoom & drag behavior in plot demo/charts instead of context menu demo

* Code review suggestions - use AxisBools::any()

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* Simplify allow_drag and allow_zoom APIs to take in Into<AxisBools>

* Remove unnecessary using...

* Remove unrelated change

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

CHANGELOG.md

@@ -7,7 +7,7 @@ NOTE: [`epaint`](crates/epaint/CHANGELOG.md), [`eframe`](crates/eframe/CHANGELOG
 ## Unreleased
 * Add `char_limit` to `TextEdit` singleline mode to limit the amount of characters
 * ⚠️ BREAKING: `Plot::link_axis` and `Plot::link_cursor` now take the name of the group ([#2410](https://github.com/emilk/egui/pull/2410)).
-
+* Update `Plot::allow_zoom` and `Plot::allow_drag` to allow setting those values for X and Y axes independently ([#2901](https://github.com/emilk/egui/pull/2901)).
 
 ## 0.21.0 - 2023-02-08 - Deadlock fix and style customizability
 * ⚠️ BREAKING: `egui::Context` now use closures for locking ([#2625](https://github.com/emilk/egui/pull/2625)):

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

@@ -72,15 +72,19 @@ impl Default for CoordinatesFormatter {
 const MIN_LINE_SPACING_IN_POINTS: f64 = 6.0; // TODO(emilk): large enough for a wide label
 
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-struct AxisBools {
+pub struct AxisBools {
-    x: bool,
+    pub x: bool,
-    y: bool,
+    pub y: bool,
 }
 
 impl AxisBools {
+    pub fn new(x: bool, y: bool) -> Self {
+        Self { x, y }
+    }
+
     #[inline]
-    fn any(&self) -> bool {
+    pub fn any(&self) -> bool {
         self.x || self.y
     }
 }
@@ -165,8 +169,8 @@ pub struct Plot {
 
     center_x_axis: bool,
     center_y_axis: bool,
-    allow_zoom: bool,
+    allow_zoom: AxisBools,
-    allow_drag: bool,
+    allow_drag: AxisBools,
     allow_scroll: bool,
     allow_double_click_reset: bool,
     allow_boxed_zoom: bool,
@@ -207,8 +211,8 @@ impl Plot {
 
             center_x_axis: false,
             center_y_axis: false,
-            allow_zoom: true,
+            allow_zoom: true.into(),
-            allow_drag: true,
+            allow_drag: true.into(),
             allow_scroll: true,
             allow_double_click_reset: true,
             allow_boxed_zoom: true,
@@ -305,8 +309,13 @@ impl Plot {
     }
 
     /// Whether to allow zooming in the plot. Default: `true`.
-    pub fn allow_zoom(mut self, on: bool) -> Self {
+    ///
-        self.allow_zoom = on;
+    /// Note: Allowing zoom in one axis but not the other may lead to unexpected results if used in combination with `data_aspect`.
+    pub fn allow_zoom<T>(mut self, on: T) -> Self
+    where
+        T: Into<AxisBools>,
+    {
+        self.allow_zoom = on.into();
         self
     }
 
@@ -346,8 +355,11 @@ impl Plot {
     }
 
     /// Whether to allow dragging in the plot to move the bounds. Default: `true`.
-    pub fn allow_drag(mut self, on: bool) -> Self {
+    pub fn allow_drag<T>(mut self, on: T) -> Self
-        self.allow_drag = on;
+    where
+        T: Into<AxisBools>,
+    {
+        self.allow_drag = on.into();
         self
     }
 
@@ -829,9 +841,16 @@ impl Plot {
         }
 
         // Dragging
-        if allow_drag && response.dragged_by(PointerButton::Primary) {
+        if allow_drag.any() && response.dragged_by(PointerButton::Primary) {
             response = response.on_hover_cursor(CursorIcon::Grabbing);
-            transform.translate_bounds(-response.drag_delta());
+            let mut delta = -response.drag_delta();
+            if !allow_drag.x {
+                delta.x = 0.0;
+            }
+            if !allow_drag.y {
+                delta.y = 0.0;
+            }
+            transform.translate_bounds(delta);
             bounds_modified = true.into();
         }
 
@@ -889,12 +908,18 @@ impl Plot {
 
         let hover_pos = response.hover_pos();
         if let Some(hover_pos) = hover_pos {
-            if allow_zoom {
+            if allow_zoom.any() {
-                let zoom_factor = if data_aspect.is_some() {
+                let mut zoom_factor = if data_aspect.is_some() {
                     Vec2::splat(ui.input(|i| i.zoom_delta()))
                 } else {
                     ui.input(|i| i.zoom_delta_2d())
                 };
+                if !allow_zoom.x {
+                    zoom_factor.x = 1.0;
+                }
+                if !allow_zoom.y {
+                    zoom_factor.y = 1.0;
+                }
                 if zoom_factor != Vec2::splat(1.0) {
                     transform.zoom(zoom_factor, hover_pos);
                     bounds_modified = true.into();

crates/egui_demo_lib/src/demo/plot_demo.rs

@@ -1,7 +1,7 @@
 use std::f64::consts::TAU;
 use std::ops::RangeInclusive;
 
-use egui::plot::{GridInput, GridMark};
+use egui::plot::{AxisBools, GridInput, GridMark};
 use egui::*;
 use plot::{
     Arrows, Bar, BarChart, BoxElem, BoxPlot, BoxSpread, CoordinatesFormatter, Corner, HLine,
@@ -812,6 +812,8 @@ impl Default for Chart {
 struct ChartsDemo {
     chart: Chart,
     vertical: bool,
+    allow_zoom: AxisBools,
+    allow_drag: AxisBools,
 }
 
 impl Default for ChartsDemo {
@@ -819,22 +821,44 @@ impl Default for ChartsDemo {
         Self {
             vertical: true,
             chart: Chart::default(),
+            allow_zoom: true.into(),
+            allow_drag: true.into(),
         }
     }
 }
 
 impl ChartsDemo {
     fn ui(&mut self, ui: &mut Ui) -> Response {
-        ui.label("Type:");
         ui.horizontal(|ui| {
-            ui.selectable_value(&mut self.chart, Chart::GaussBars, "Histogram");
+            ui.vertical(|ui| {
-            ui.selectable_value(&mut self.chart, Chart::StackedBars, "Stacked Bar Chart");
+                ui.label("Type:");
-            ui.selectable_value(&mut self.chart, Chart::BoxPlot, "Box Plot");
+                ui.horizontal(|ui| {
-        });
+                    ui.selectable_value(&mut self.chart, Chart::GaussBars, "Histogram");
-        ui.label("Orientation:");
+                    ui.selectable_value(&mut self.chart, Chart::StackedBars, "Stacked Bar Chart");
-        ui.horizontal(|ui| {
+                    ui.selectable_value(&mut self.chart, Chart::BoxPlot, "Box Plot");
-            ui.selectable_value(&mut self.vertical, true, "Vertical");
+                });
-            ui.selectable_value(&mut self.vertical, false, "Horizontal");
+                ui.label("Orientation:");
+                ui.horizontal(|ui| {
+                    ui.selectable_value(&mut self.vertical, true, "Vertical");
+                    ui.selectable_value(&mut self.vertical, false, "Horizontal");
+                });
+            });
+            ui.vertical(|ui| {
+                ui.group(|ui| {
+                    ui.add_enabled_ui(self.chart != Chart::StackedBars, |ui| {
+                        ui.horizontal(|ui| {
+                            ui.label("Allow zoom:");
+                            ui.checkbox(&mut self.allow_zoom.x, "X");
+                            ui.checkbox(&mut self.allow_zoom.y, "Y");
+                        });
+                    });
+                    ui.horizontal(|ui| {
+                        ui.label("Allow drag:");
+                        ui.checkbox(&mut self.allow_drag.x, "X");
+                        ui.checkbox(&mut self.allow_drag.y, "Y");
+                    });
+                });
+            });
         });
         match self.chart {
             Chart::GaussBars => self.bar_gauss(ui),
@@ -867,6 +891,8 @@ impl ChartsDemo {
         Plot::new("Normal Distribution Demo")
             .legend(Legend::default())
             .clamp_grid(true)
+            .allow_zoom(self.allow_zoom)
+            .allow_drag(self.allow_drag)
             .show(ui, |plot_ui| plot_ui.bar_chart(chart))
             .response
     }
@@ -925,6 +951,7 @@ impl ChartsDemo {
         Plot::new("Stacked Bar Chart Demo")
             .legend(Legend::default())
             .data_aspect(1.0)
+            .allow_drag(self.allow_drag)
             .show(ui, |plot_ui| {
                 plot_ui.bar_chart(chart1);
                 plot_ui.bar_chart(chart2);
@@ -968,6 +995,8 @@ impl ChartsDemo {
 
         Plot::new("Box Plot Demo")
             .legend(Legend::default())
+            .allow_zoom(self.allow_zoom)
+            .allow_drag(self.allow_drag)
             .show(ui, |plot_ui| {
                 plot_ui.box_plot(box1);
                 plot_ui.box_plot(box2);