Added bar plot support

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