Simplify heatmap code (#209)

Rather than returning result, just display empty figure on invalid
number rows/cols

Author: michalsustr

egui_plot/src/items/heatmap.rs

@@ -38,25 +38,6 @@ pub const BASE_COLORS: [Color32; 10] = [
     Color32::from_rgb(122, 4, 2),
 ];
 
-#[derive(Debug)]
-pub enum HeatmapErr {
-    ZeroColumns,
-    ZeroRows,
-    BadLength,
-}
-
-impl std::fmt::Display for HeatmapErr {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Self::ZeroColumns => write!(f, "number of columns must not be zero"),
-            Self::ZeroRows => write!(f, "number of rows must not be zero"),
-            Self::BadLength => write!(f, "length of value vector is not divisible by number of columns"),
-        }
-    }
-}
-
-impl std::error::Error for HeatmapErr {}
-
 /// Default resolution for heatmap color palette
 pub const DEFAULT_RESOLUTION: usize = 128;
 
@@ -134,9 +115,8 @@ impl Heatmap {
     /// Create a 2D heatmap. Will automatically infer number of rows.
     ///
     /// - `values` contains magnitude of each tile. The alignment is row by row.
-    /// - `cols` is the number of columns (i.e. the length of each row) and must
-    ///   not be zero.
-    /// - `values.len()` must be a multiple of `cols`.
+    /// - `cols` is the number of columns (i.e. the length of each row).
+    /// - `values.len()` should be a multiple of `cols`.
     ///
     /// Example: To display this
     ///
@@ -146,23 +126,15 @@ impl Heatmap {
     ///
     /// pass `values = vec![0.0, 0.1, 0.3, 0.4]` and `cols = 2`.
     ///
-    /// Returns error type if provided parameters are inconsistent
-    ///
-    /// # Errors
-    /// - `HeatmapErr::ZeroColumns` if `cols` is zero
-    /// - `HeatmapErr::ZeroRows` if `values` is empty
-    /// - `HeatmapErr::BadLength` if `values.len()` is not divisible by `cols`
-    pub fn new(values: Vec<f64>, cols: usize) -> Result<Self, HeatmapErr> {
-        if cols == 0 {
-            return Err(HeatmapErr::ZeroColumns);
-        }
-        if (values.len() % cols) != 0 {
-            return Err(HeatmapErr::BadLength);
+    /// If parameters are invalid (e.g., `cols` is zero, `values` is empty, or
+    /// `values.len()` is not divisible by `cols`), an empty heatmap is created.
+    pub fn new(values: Vec<f64>, cols: usize) -> Self {
+        // Handle invalid parameters by creating an empty heatmap
+        if cols == 0 || values.is_empty() || (values.len() % cols) != 0 {
+            return Self::empty();
         }
+
         let rows = values.len() / cols;
-        if rows == 0 {
-            return Err(HeatmapErr::ZeroRows);
-        }
 
         // determine range
         let mut min = f64::MAX;
@@ -174,7 +146,7 @@ impl Heatmap {
 
         let resolution = DEFAULT_RESOLUTION;
 
-        Ok(Self {
+        Self {
             base: PlotItemBase::new(String::new()),
             pos: PlotPoint { x: 0.0, y: 0.0 },
             values,
@@ -190,7 +162,29 @@ impl Heatmap {
             highlight: false,
             name: String::new(),
             tile_size: Vec2 { x: 1.0, y: 1.0 },
-        })
+        }
+    }
+
+    /// Create an empty heatmap (no tiles).
+    fn empty() -> Self {
+        let resolution = DEFAULT_RESOLUTION;
+        Self {
+            base: PlotItemBase::new(String::new()),
+            pos: PlotPoint { x: 0.0, y: 0.0 },
+            values: Vec::new(),
+            cols: 0,
+            rows: 0,
+            min: 0.0,
+            max: 0.0,
+            formatter: Box::new(|v| format!("{v:.1}")),
+            custom_mapping: None,
+            show_labels: true,
+            resolution,
+            palette: Self::linear_gradient_from_base_colors(&BASE_COLORS, resolution),
+            highlight: false,
+            name: String::new(),
+            tile_size: Vec2 { x: 1.0, y: 1.0 },
+        }
     }
 
     /// Set the resolution of the color palette.

egui_plot/src/items/mod.rs

@@ -22,7 +22,6 @@ use egui::pos2;
 use egui::vec2;
 use emath::Float as _;
 pub use heatmap::Heatmap;
-pub use heatmap::HeatmapErr;
 pub use line::HLine;
 pub use line::VLine;
 pub use plot_image::PlotImage;

egui_plot/src/items/span.rs

@@ -29,9 +29,9 @@ use crate::utils::find_name_candidate;
 /// Padding between the label of the span and both the edge of the view and the
 /// span borders.
 ///
-/// For example, for a horizontal span, this is the padding between the top of the span
-/// label and the top edge of the plot view, but also the margin between the left/right
-/// edges of the span and the span label.
+/// For example, for a horizontal span, this is the padding between the top of
+/// the span label and the top edge of the plot view, but also the margin
+/// between the left/right edges of the span and the span label.
 const LABEL_PADDING: f32 = 4.0;
 
 /// A span covering a range on either axis.

egui_plot/src/lib.rs

@@ -43,7 +43,6 @@ pub use crate::items::BoxSpread;
 pub use crate::items::ClosestElem;
 pub use crate::items::HLine;
 pub use crate::items::Heatmap;
-pub use crate::items::HeatmapErr;
 pub use crate::items::Line;
 pub use crate::items::LineStyle;
 pub use crate::items::MarkerShape;

examples/heatmap/src/app.rs

@@ -55,8 +55,8 @@ impl HeatmapDemo {
             });
             ui.group(|ui| {
                 ui.vertical(|ui| {
-                    ui.add(egui::Slider::new(&mut self.rows, 1..=50).text("Rows"));
-                    ui.add(egui::Slider::new(&mut self.cols, 1..=50).text("Columns"));
+                    ui.add(egui::Slider::new(&mut self.rows, 0..=50).text("Rows"));
+                    ui.add(egui::Slider::new(&mut self.cols, 0..=50).text("Columns"));
                 });
             });
             ui.group(|ui| {
@@ -94,7 +94,6 @@ impl HeatmapDemo {
         }
 
         let heatmap = egui_plot::Heatmap::new(values, self.cols)
-            .expect("Failed to create heatmap")
             .palette(&self.palette)
             .highlight(true)
             .show_labels(self.show_labels);