Support different grid types depending on the plot

Categorical views only show horizontal lines, whereas continuous views
show lines in both directions.

Author: simonrw

examples/with_grid.rs

@@ -1,16 +1,42 @@
 extern crate plotlib;
 
 use plotlib::grid::Grid;
+use plotlib::style::BarChart;
 use plotlib::style::Line;
 use plotlib::view::View;
 
 fn main() {
+    render_line_chart("line_with_grid.svg");
+    render_barchart("barchart_with_grid.svg");
+}
+
+fn render_line_chart<S>(filename: S)
+where
+    S: AsRef<str>,
+{
     let l1 = plotlib::line::Line::new(&[(0., 1.), (2., 1.5), (3., 1.2), (4., 1.1)])
         .style(plotlib::line::Style::new().colour("burlywood"));
-    let grid = Grid::new(3, 8);
     let mut v = plotlib::view::ContinuousView::new().add(&l1);
-    v.add_grid(grid);
+    v.add_grid(Grid::new(3, 8));
+    plotlib::page::Page::single(&v)
+        .save(filename.as_ref())
+        .expect("saving svg");
+}
+
+fn render_barchart<S>(filename: S)
+where
+    S: AsRef<str>,
+{
+    let b1 = plotlib::barchart::BarChart::new(5.3).label("1");
+    let b2 = plotlib::barchart::BarChart::new(2.6)
+        .label("2")
+        .style(plotlib::barchart::Style::new().fill("darkolivegreen"));
+    let mut v = plotlib::view::CategoricalView::new()
+        .add(&b1)
+        .add(&b2)
+        .x_label("Experiment");
+    v.add_grid(Grid::new(3, 8));
     plotlib::page::Page::single(&v)
-        .save("line.svg")
+        .save(filename.as_ref())
         .expect("saving svg");
 }

src/grid.rs

@@ -1,3 +1,8 @@
+pub(crate) enum GridType<'a> {
+    HorizontalOnly(&'a Grid),
+    Both(&'a Grid),
+}
+
 pub struct Grid {
     pub nx: u32,
     pub ny: u32,

src/page.rs

@@ -25,16 +25,23 @@ pub struct Page<'a> {
 
 impl<'a> Page<'a> {
     /**
-    Creates a plot containing a single view
+    Creates an empty page container for plots to be added to
     */
-    pub fn single(view: &'a View) -> Self {
+    pub fn empty() -> Self {
         Page {
-            views: vec![view],
-            num_views: 1,
+            views: Vec::new(),
+            num_views: 0,
             dimensions: (600, 400),
         }
     }
 
+    /**
+    Creates a plot containing a single view
+    */
+    pub fn single(view: &'a View) -> Self {
+        Page::empty().add_plot(view)
+    }
+
     /// Set the dimensions of the plot.
     pub fn dimensions(mut self, x: u32, y: u32) -> Self {
         self.dimensions = (x, y);

src/svg_render.rs

@@ -4,7 +4,7 @@ use svg::node;
 use svg::Node;
 
 use crate::axis;
-use crate::grid::Grid;
+use crate::grid::GridType;
 use crate::histogram;
 use crate::style;
 use crate::utils;
@@ -448,28 +448,45 @@ where
     group
 }
 
-pub(crate) fn draw_grid(grid: &Grid, face_width: f64, face_height: f64) -> node::element::Group {
-    let (xmin, xmax) = (0f64, face_width);
-    let (ymin, ymax) = (0f64, face_height);
+pub(crate) fn draw_grid(grid: GridType, face_width: f64, face_height: f64) -> node::element::Group {
+    match grid {
+        GridType::HorizontalOnly(grid) => {
+            let (ymin, ymax) = (0f64, face_height);
+            let y_step = (ymax - ymin) / f64::from(grid.ny);
+            let mut lines = node::element::Group::new();
+
+            for iy in 0..=grid.ny {
+                let y = f64::from(iy) * y_step + ymin;
+                let line = horizontal_line(-y, 0.0, face_width, grid.color.as_str());
+                lines = lines.add(line);
+            }
 
-    let x_step = (xmax - xmin) / f64::from(grid.nx);
-    let y_step = (ymax - ymin) / f64::from(grid.ny);
+            lines
+        }
+        GridType::Both(grid) => {
+            let (xmin, xmax) = (0f64, face_width);
+            let (ymin, ymax) = (0f64, face_height);
 
-    let mut lines = node::element::Group::new();
+            let x_step = (xmax - xmin) / f64::from(grid.nx);
+            let y_step = (ymax - ymin) / f64::from(grid.ny);
 
-    for iy in 0..=grid.ny {
-        let y = f64::from(iy) * y_step + ymin;
-        let line = horizontal_line(-y, 0.0, face_width, grid.color.as_str());
-        lines = lines.add(line);
-    }
+            let mut lines = node::element::Group::new();
 
-    for ix in 0..=grid.nx {
-        let x = f64::from(ix) * x_step + xmin;
-        let line = vertical_line(x, 0.0, -face_height, grid.color.as_str());
-        lines = lines.add(line);
-    }
+            for iy in 0..=grid.ny {
+                let y = f64::from(iy) * y_step + ymin;
+                let line = horizontal_line(-y, 0.0, face_width, grid.color.as_str());
+                lines = lines.add(line);
+            }
 
-    lines
+            for ix in 0..=grid.nx {
+                let x = f64::from(ix) * x_step + xmin;
+                let line = vertical_line(x, 0.0, -face_height, grid.color.as_str());
+                lines = lines.add(line);
+            }
+
+            lines
+        }
+    }
 }
 
 #[cfg(test)]

src/view.rs

@@ -14,7 +14,7 @@ use svg::Node;
 
 use crate::axis;
 use crate::errors::Result;
-use crate::grid::Grid;
+use crate::grid::{Grid, GridType};
 use crate::representation::{CategoricalRepresentation, ContinuousRepresentation};
 use crate::svg_render;
 use crate::text_render;
@@ -171,7 +171,11 @@ impl<'a> View for ContinuousView<'a> {
         view_group.append(svg_render::draw_y_axis(&y_axis, face_height));
 
         if let Some(grid) = &self.grid {
-            view_group.append(svg_render::draw_grid(grid, face_width, face_height));
+            view_group.append(svg_render::draw_grid(
+                GridType::Both(grid),
+                face_width,
+                face_height,
+            ));
         }
 
         Ok(view_group)
@@ -369,6 +373,15 @@ impl<'a> View for CategoricalView<'a> {
         // Add in the axes
         view_group.append(svg_render::draw_categorical_x_axis(&x_axis, face_width));
         view_group.append(svg_render::draw_y_axis(&y_axis, face_height));
+
+        if let Some(grid) = &self.grid {
+            view_group.append(svg_render::draw_grid(
+                GridType::HorizontalOnly(grid),
+                face_width,
+                face_height,
+            ));
+        }
+
         Ok(view_group)
     }