Added bar plot support

README.md

@@ -52,10 +52,10 @@ See below for an overview of the progress.
 - [ ] Plotting functionality
   - [x] Line plot
   - [x] Text plot
-  - [ ] Scatter plot
-  - [ ] Bar plot
-    - [ ] Vertical
-    - [ ] Horizontal
+  - [x] Scatter plot
+  - [x] Bar plot
+    - [x] Vertical
+    - [x] Horizontal
   - [ ] Error bar plot
     - [ ] Vertical
     - [ ] Horizontal

implot-examples/examples/bar_plots.rs

@@ -0,0 +1,76 @@
+//! This example demonstrates how bar plots 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::{push_style_var_f32, push_style_var_u32, Marker, Plot, PlotBars, StyleVar};
+
+mod support;
+
+fn show_basic_vertical_plot(ui: &Ui) {
+    ui.text(im_str!("This header shows a simple vertical bar plot."));
+    let content_width = ui.window_content_region_width();
+    Plot::new("Vertical bar 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(|| {
+            // If this is called outside a plot build callback, the program will panic.
+            let axis_positions = vec![0.2, 0.4, 0.6, 0.8];
+            let values = vec![0.1, 0.2, 0.3, 0.4];
+            PlotBars::new("legend label")
+                .with_bar_width(0.1)
+                .plot(&axis_positions, &values);
+        });
+}
+
+fn show_basic_horizontal_plot(ui: &Ui) {
+    ui.text(im_str!("This header shows a simple horizontal bar plot."));
+    let content_width = ui.window_content_region_width();
+    Plot::new("Horizontal bar 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(|| {
+            // If this is called outside a plot build callback, the program will panic.
+            let axis_positions = vec![0.2, 0.4, 0.6, 0.8];
+            let values = vec![0.1, 0.2, 0.3, 0.4];
+            PlotBars::new("legend label")
+                .with_bar_width(0.05)
+                .with_horizontal_bars()
+                .plot(&axis_positions, &values);
+        });
+}
+
+fn main() {
+    let system = support::init(file!());
+    let mut showing_demo = false;
+    system.main_loop(move |_, ui| {
+        Window::new(im_str!("Line plots 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 bar 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 \
+                    (by enabling the 'Show demo' checkbox) for instructions \
+                    on how to interact with ImPlot plots."
+                ));
+
+                ui.checkbox(im_str!("Show demo"), &mut showing_demo);
+
+                // Show individual examples in collapsed headers
+                if CollapsingHeader::new(im_str!("Basic vertical plot")).build(&ui) {
+                    show_basic_vertical_plot(&ui);
+                }
+
+                if CollapsingHeader::new(im_str!("Basic horizontal plot")).build(&ui) {
+                    show_basic_horizontal_plot(&ui);
+                }
+            });
+
+        if showing_demo {
+            implot::show_demo_window(&mut showing_demo);
+        }
+    });
+}

implot-examples/examples/scatter_plots.rs

@@ -8,7 +8,7 @@ mod support;
 
 fn show_basic_plot(ui: &Ui) {
     ui.text(im_str!(
-        "This header just plots a line with as little code as possible."
+        "This header just draws a scatter plot with as little code as possible."
     ));
     let content_width = ui.window_content_region_width();
     Plot::new("Simple scatter plot")

src/lib.rs

@@ -444,7 +444,7 @@ impl PlotLine {
 
 /// Struct to provide functionality for creating a scatter plot
 pub struct PlotScatter {
-    /// Label to show in the legend for this line
+    /// Label to show in the legend for this scatter plot
     label: String,
 }
 
@@ -476,6 +476,82 @@ impl PlotScatter {
     }
 }
 
+/// Struct to provide bar plotting functionality.
+pub struct PlotBars {
+    /// Label to show in the legend for this line
+    label: String,
+
+    /// Width of the bars, in plot coordinate terms
+    bar_width: f64,
+
+    /// Horizontal bar mode
+    horizontal_bars: bool,
+}
+
+impl PlotBars {
+    /// Create a new bar plot to be shown. Defaults to drawing vertical bars.
+    /// Does not draw anything yet.
+    pub fn new(label: &str) -> Self {
+        Self {
+            label: label.to_owned(),
+            bar_width: 0.67, // Default value taken from C++ implot
+            horizontal_bars: false,
+        }
+    }
+
+    /// Set the width of the bars
+    pub fn with_bar_width(mut self, bar_width: f64) -> Self {
+        self.bar_width = bar_width;
+        self
+    }
+
+    /// Set the bars to be horizontal (default is vertical)
+    pub fn with_horizontal_bars(mut self) -> Self {
+        self.horizontal_bars = true;
+        self
+    }
+
+    /// Draw a previously-created bar plot. Use this in closures passed to
+    /// [`Plot::build()`](struct.Plot.html#method.build). The `axis_positions`
+    /// specify where on the corersponding axis (X for vertical mode, Y for horizontal mode) the
+    /// bar is drawn, and the `bar_values` specify what values the bars have.
+    pub fn plot(&self, axis_positions: &Vec<f64>, bar_values: &Vec<f64>) {
+        let number_of_points = axis_positions.len().min(bar_values.len());
+        // If there is no data to plot, we stop here
+        if number_of_points == 0 {
+            return;
+        }
+        unsafe {
+            // C++ implot has separate functions for the two variants, but the interfaces
+            // are the same, so they are unified here. The x and y values have different
+            // meanings though, hence the swapping around before they are passed to the
+            // plotting function.
+            let (plot_function, x, y);
+            if self.horizontal_bars {
+                plot_function = sys::ImPlot_PlotBarsHdoublePtrdoublePtr
+                    as unsafe extern "C" fn(*const i8, *const f64, *const f64, i32, f64, i32, i32);
+                x = bar_values;
+                y = axis_positions;
+            } else {
+                plot_function = sys::ImPlot_PlotBarsdoublePtrdoublePtr
+                    as unsafe extern "C" fn(*const i8, *const f64, *const f64, i32, f64, i32, i32);
+                x = axis_positions;
+                y = bar_values;
+            };
+
+            plot_function(
+                im_str!("{}", self.label).as_ptr() as *const i8,
+                x.as_ptr(),
+                y.as_ptr(),
+                number_of_points as i32, // "as" casts saturate as of Rust 1.45. This is safe here.
+                self.bar_width,
+                0,                                 // No offset
+                std::mem::size_of::<f64>() as i32, // Stride, set to one f64 for the standard use case
+            );
+        }
+    }
+}
+
 /// Struct to provide functionality for adding text within a plot
 pub struct PlotText {
     /// Label to show in plot