Added heatmap support. See comments.

The basic functionality seems to work, though setting the drawing area
seems buggy. I'll have to investigate more.

implot-examples/examples-shared/src/heatmaps.rs

@@ -0,0 +1,40 @@
+//! This example demonstrates how heatmaps are to be used. For more general
+//! features of the libray, see the line_plots example.
+
+use imgui::{im_str, CollapsingHeader, Condition, Ui, Window};
+use implot::{Plot, PlotHeatmap, PlotUi};
+
+pub fn show_basic_heatmap(ui: &Ui, plot_ui: &PlotUi) {
+    ui.text(im_str!("This header shows a simple heatmap"));
+    let content_width = ui.window_content_region_width();
+    Plot::new("Heatmap plot")
+        // The size call could also be omitted, though the defaults don't consider window
+        // width, which is why we're not doing so here.
+        .size(content_width, 300.0)
+        .build(plot_ui, || {
+            let values = (0..100).map(|x| 0.1 * x as f64).collect::<Vec<_>>();
+            PlotHeatmap::new("my favourite heatmap")
+                // If you omit the with_scale call, the range will be computed based on the values
+                .with_scale(0.0, 10.0)
+                .plot(&values, 10, 10);
+        });
+}
+
+pub fn show_demo_window(ui: &Ui, plot_ui: &PlotUi) {
+    Window::new(im_str!("Heatmaps example"))
+        .size([430.0, 450.0], Condition::FirstUseEver)
+        .build(ui, || {
+            ui.text(im_str!("Hello from implot-rs!"));
+            ui.text_wrapped(im_str!(
+                "The headers here demo the heatmap plotting features of the library. \
+                 Have a look at the example source code to see how they are implemented.\n\
+                 Check out the demo from ImPlot itself first \
+                 for instructions on how to interact with ImPlot plots."
+            ));
+
+            // Show individual examples in collapsed headers
+            if CollapsingHeader::new(im_str!("Basic vertical plot")).build(&ui) {
+                show_basic_heatmap(&ui, &plot_ui);
+            }
+        });
+}

implot-examples/examples-shared/src/lib.rs

@@ -1,4 +1,5 @@
 pub mod bar_plots;
+pub mod heatmaps;
 pub mod line_plots;
 pub mod scatter_plots;
 pub mod stairs_plots;
@@ -13,4 +14,5 @@ pub fn show_demos(ui: &Ui, plot_ui: &PlotUi) {
     scatter_plots::show_demo_window(ui, plot_ui);
     text_plots::show_demo_window(ui, plot_ui);
     stairs_plots::show_demo_window(ui, plot_ui);
+    heatmaps::show_demo_window(ui, plot_ui);
 }