chart: Add labels support

gallery/barchart.typ

@@ -1,4 +1,4 @@
-#import "@preview/cetz:0.2.0": canvas, chart
+#import "@preview/cetz:0.2.0": canvas, chart, draw
 
 #set page(width: auto, height: auto, margin: .5cm)
 
@@ -12,11 +12,14 @@
 )
 
 #canvas({
+  draw.set-style(legend: (fill: white))
   chart.barchart(mode: "clustered",
                  size: (9, auto),
                  label-key: 0,
                  value-key: (..range(1, 5)),
                  bar-width: .8,
                  x-tick-step: 2.5,
-                 data2)
+                 data2,
+                 labels: ([Low], [Medium], [High], [Very high]),
+                 legend: "legend.inner-north-east",)
 })

src/lib/chart/barchart.typ

@@ -46,6 +46,7 @@
 /// - x-unit (content,auto): Tick suffix added to each tick label
 /// - y-label (content,none): Y axis label
 /// - x-label (content,none): x axis label
+/// - labels (none,content): Legend labels per x value group
 /// - ..plot-args (any): Arguments to pass to `plot.plot`
 #let barchart(data,
               label-key: 0,
@@ -56,6 +57,7 @@
               x-label: none,
               x-unit: auto,
               y-label: none,
+              labels: none,
               ..plot-args
               ) = {
   assert(type(label-key) in (int, str))
@@ -94,7 +96,6 @@
       root: "barchart", base: barchart-default-style)
     draw.set-style(..style)
 
-
     let y-inset = calc.max(style.y-inset, style.bar-width / 2)
     plot.plot(size: size,
               axis-style: "scientific-auto",
@@ -110,7 +111,8 @@
     {
       plot.add-bar(data,
         mode: mode,
-        bar-width: style.bar-width,
+        labels: labels,
+        bar-width: -style.bar-width,
         axes: ("y", "x"))
     })
   })

src/lib/chart/columnchart.typ

@@ -47,6 +47,7 @@
 /// - y-unit (content,auto): Tick suffix added to each tick label
 /// - y-label (content,none): Y axis label
 /// - x-label (content,none): x axis label
+/// - labels (none,content): Legend labels per y value group
 /// - ..plot-args (any): Arguments to pass to `plot.plot`
 #let columnchart(data,
                  label-key: 0,
@@ -57,6 +58,7 @@
                  x-label: none,
                  y-unit: auto,
                  y-label: none,
+                 labels: none,
                  ..plot-args
                  ) = {
   assert(type(label-key) in (int, str))
@@ -110,6 +112,7 @@
     {
       plot.add-bar(data,
         mode: mode,
+        labels: labels,
         bar-width: style.bar-width,
         axes: ("x", "y"))
     })

src/lib/plot/bar.typ

@@ -104,7 +104,7 @@
     message: "Mode must be basic, clustered, stacked or stacked100, but is " + mode)
   assert(bar-position in ("start", "center", "end"),
     message: "Invalid bar-position '" + bar-position + "'. Allowed values are: start, center, end")
-  assert(bar-width > 0,
+  assert(bar-width != 0,
     message: "Option bar-width must be > 0, but is " + str(bar-width))
 
   let n = util.max(..data.map(d => d.len() - 1))