Parametrize formatting variables

examples/hello_world.roc

@@ -7,7 +7,7 @@ config =
     {
         outputFilePath: "./examples/hello_world.svg",
         title: "Hello, World!",
-        subtitle: "This data is coming from Roc ☺",
+        subtitle: "",
         width: 1024,
         height: 768,
         lines: [
@@ -16,6 +16,26 @@ config =
             { name: "sine", color: blue, points: sin },
             { name: "sine x 2", color: red, points: sinX2 },
         ],
+        bounds: {
+            xMin: -3.2,
+            xMax: 3.2,
+            yMin: -2.1,
+            yMax: 2.1,
+        },
+        fonts: {
+            titleFamily: "sans-serif",
+            titleSize: 60,
+            subtitleFamily: "sans-serif",
+            subtitleSize: 40,
+        },
+        labels: {
+            xCount: 20,
+            yCount: 10,
+        },
+        layout: {
+            chartMargin: 5,
+            labelArea: 50,
+        },
     }
 
 pi = 3.141592653589793

platform/Config.roc

@@ -2,6 +2,14 @@ interface Config
     exposes [ Config, black, white, red, green, blue, cyan, magenta, yellow ]
     imports []
 
+Bounds :
+    {
+        xMin: F64,
+        xMax: F64,
+        yMin: F64,
+        yMax: F64,
+    }
+
 # TODO: probably move some of this into a different module.
 Color :
     {
@@ -19,6 +27,26 @@ cyan = { r: 0, g: 255, b: 255 }
 magenta = { r: 255, g: 0, b: 255 }
 yellow = { r: 255, g: 255, b: 0 }
 
+Fonts :
+    {
+        titleFamily: Str,
+        titleSize: U32,
+        subtitleFamily: Str,
+        subtitleSize: U32,
+    }
+
+Labels :
+    {
+        xCount: Nat,
+        yCount: Nat,
+    }
+
+Layout :
+    {
+        chartMargin: U32,
+        labelArea: U32,
+    }
+
 Line :
     {
         name: Str,
@@ -35,4 +63,8 @@ Config :
         width : U32,
         height : U32,
         lines : List Line,
+        bounds : Bounds,
+        fonts : Fonts,
+        labels : Labels,
+        layout : Layout,
     }

platform/src/config.rs

@@ -7,6 +7,15 @@ pub struct P2 {
     pub y: f64,
 }
 
+#[derive(Default, Debug, Copy, Clone)]
+#[repr(C)]
+pub struct Bounds {
+    pub xMax: f64,
+    pub xMin: f64,
+    pub yMax: f64,
+    pub yMin: f64,
+}
+
 #[derive(Default, Debug, Copy, Clone)]
 #[repr(C)]
 pub struct Color {
@@ -15,6 +24,29 @@ pub struct Color {
     pub r: u8,
 }
 
+#[derive(Default, Debug)]
+#[repr(C)]
+pub struct Fonts {
+    pub subtitleFamily: RocStr,
+    pub titleFamily: RocStr,
+    pub subtitleSize: u32,
+    pub titleSize: u32,
+}
+
+#[derive(Default, Debug)]
+#[repr(C)]
+pub struct Labels {
+    pub xCount: usize,
+    pub yCount: usize,
+}
+
+#[derive(Default, Debug)]
+#[repr(C)]
+pub struct Layout {
+    pub chartMargin: u32,
+    pub labelArea: u32,
+}
+
 #[derive(Default, Debug)]
 #[repr(C)]
 pub struct Line {
@@ -26,11 +58,15 @@ pub struct Line {
 #[derive(Default, Debug)]
 #[repr(C)]
 pub struct Config {
+    pub bounds: Bounds,
+    pub fonts: Fonts,
+    pub labels: Labels,
     pub lines: RocList<Line>,
     pub output_file_path: RocStr,
     pub subtitle: RocStr,
     pub title: RocStr,
     pub height: u32,
+    pub layout: Layout,
     pub width: u32,
 }
 

platform/src/plot.rs

@@ -19,10 +19,30 @@ fn construct_area<Backend: DrawingBackend>(
 ) -> Result<DrawingArea<Backend, Shift>, DrawingAreaErrorKind<Backend::ErrorType>> {
     let area = backend.into_drawing_area();
     area.fill(&WHITE)?;
-    let area = area.titled(config.title.as_str(), ("sans-serif", 60))?;
+    let area = area.titled(
+        config.title.as_str(),
+        (config.fonts.titleFamily.as_str(), config.fonts.titleSize),
+    )?;
     Ok(area)
 }
 
+fn construct_builder<'a, Backend: DrawingBackend>(
+    area: &'a DrawingArea<Backend, Shift>,
+    config: &'a Config,
+) -> ChartBuilder<'a, 'a, Backend> {
+    let subtitle = config.subtitle.as_str();
+    let mut builder = ChartBuilder::on(area);
+    builder.margin(config.layout.chartMargin)
+        .set_all_label_area_size(config.layout.labelArea);
+    if subtitle.len() > 0 {
+        builder.caption(
+            config.subtitle.as_str(),
+            (config.fonts.subtitleFamily.as_str(), config.fonts.subtitleSize),
+        );
+    }
+    return builder;
+}
+
 fn construct_bitmap_backend(config: &Config) -> BitMapBackend {
     BitMapBackend::new(
         config.output_file_path.as_str(),
@@ -42,26 +62,26 @@ fn plot_with<Backend: DrawingBackend>(
     config: &Config,
 ) -> Result<(), DrawingAreaErrorKind<Backend::ErrorType>> {
     let area = construct_area(backend, config)?;
-    let mut cc = ChartBuilder::on(&area)
-        .margin(5)
-        .set_all_label_area_size(50)
-        .caption(config.subtitle.as_str(), ("sans-serif", 40))
-        .build_cartesian_2d(-3.2f64..3.2f64, -2.1f64..2.1f64)?;
-    cc.configure_mesh()
-        .x_labels(20)
-        .y_labels(10)
+    let mut builder = construct_builder(&area, config);
+    let mut context = builder.build_cartesian_2d(
+        config.bounds.xMin..config.bounds.xMax,
+        config.bounds.yMin..config.bounds.yMax,
+    )?;
+    context.configure_mesh()
+        .x_labels(config.labels.xCount)
+        .y_labels(config.labels.yCount)
         .disable_mesh()
-        .x_label_formatter(&|v| format!("{:.1}", v))
-        .y_label_formatter(&|v| format!("{:.1}", v))
+        .x_label_formatter(&|v| format!("{:?}", v)) // TODO: Format labels in Roc.
+        .y_label_formatter(&|v| format!("{:?}", v)) // TODO: Format labels in Roc.
         .draw()?;
     for line in config.lines.iter() {
         let v: Vec<(f64, f64)> = line.points.iter().map(|point| (point.x, point.y)).collect();
         let color = RGBColor(line.color.r, line.color.g, line.color.b);
-        cc.draw_series(LineSeries::new(v, color))?
+        context.draw_series(LineSeries::new(v, color))?
             .label(line.name.as_str())
             .legend(move |(x, y)| PathElement::new(vec![(x, y), (x + 20, y)], color));
     }
-    cc.configure_series_labels().border_style(&BLACK).draw()?;
+    context.configure_series_labels().border_style(&BLACK).draw()?;
     area.present().unwrap_or_else(|_| {
         panic!(
             "I failed to draw your plot to {} !",