Add support for axis labels in plots

ui/src/minard/components/Axes.tsx

@@ -1,6 +1,11 @@
 import React, {useRef, useLayoutEffect, SFC} from 'react'
 
-import {PlotEnv, TICK_PADDING_RIGHT, TICK_PADDING_TOP} from 'src/minard'
+import {
+  PlotEnv,
+  TICK_PADDING_RIGHT,
+  TICK_PADDING_TOP,
+  PLOT_PADDING,
+} from 'src/minard'
 import {clearCanvas} from 'src/minard/utils/clearCanvas'
 
 interface Props {
@@ -20,9 +25,13 @@ export const drawAxes = (
   const {
     width,
     height,
+    innerWidth,
+    innerHeight,
     margins,
     xTicks,
     yTicks,
+    xAxisLabel,
+    yAxisLabel,
     baseLayer: {
       scales: {x: xScale, y: yScale},
     },
@@ -77,6 +86,31 @@ export const drawAxes = (
 
     context.fillText(String(yTick), margins.left - TICK_PADDING_RIGHT, y)
   }
+
+  // Draw the x axis label
+  if (xAxisLabel) {
+    context.textAlign = 'center'
+    context.textBaseline = 'bottom'
+    context.fillText(
+      xAxisLabel,
+      margins.left + innerWidth / 2,
+      height - PLOT_PADDING
+    )
+  }
+
+  // Draw the y axis label
+  if (yAxisLabel) {
+    const x = PLOT_PADDING
+    const y = margins.top + innerHeight / 2
+
+    context.save()
+    context.translate(x, y)
+    context.rotate(-Math.PI / 2)
+    context.textAlign = 'center'
+    context.textBaseline = 'top'
+    context.fillText(yAxisLabel, 0, 0)
+    context.restore()
+  }
 }
 
 export const Axes: SFC<Props> = props => {

ui/src/minard/components/Plot.tsx

@@ -9,6 +9,8 @@ import {
   setTable,
   setControlledXDomain,
   setControlledYDomain,
+  setXAxisLabel,
+  setYAxisLabel,
 } from 'src/minard/utils/plotEnvActions'
 import {plotEnvReducer, INITIAL_PLOT_ENV} from 'src/minard/utils/plotEnvReducer'
 
@@ -29,6 +31,8 @@ export interface Props {
   axesStroke?: string
   tickFont?: string
   tickFill?: string
+  xAxisLabel?: string
+  yAxisLabel?: string
 
   // The x domain of the plot can be explicitly set. If this prop is passed,
   // then the component is operating in a "controlled" mode, where it always
@@ -53,6 +57,8 @@ export const Plot: SFC<Props> = ({
   axesStroke = '#31313d',
   tickFont = 'bold 10px Roboto',
   tickFill = '#8e91a1',
+  xAxisLabel = '',
+  yAxisLabel = '',
   xDomain = null,
   yDomain = null,
 }) => {
@@ -62,12 +68,16 @@ export const Plot: SFC<Props> = ({
     height,
     xDomain,
     yDomain,
+    xAxisLabel,
+    yAxisLabel,
     baseLayer: {...INITIAL_PLOT_ENV.baseLayer, table},
   })
 
   useMountedEffect(() => dispatch(setTable(table)), [table])
   useMountedEffect(() => dispatch(setControlledXDomain(xDomain)), [xDomain])
   useMountedEffect(() => dispatch(setControlledYDomain(yDomain)), [yDomain])
+  useMountedEffect(() => dispatch(setXAxisLabel(xAxisLabel)), [xAxisLabel])
+  useMountedEffect(() => dispatch(setYAxisLabel(yAxisLabel)), [yAxisLabel])
   useMountedEffect(() => dispatch(setDimensions(width, height)), [
     width,
     height,

ui/src/minard/index.ts

@@ -9,6 +9,8 @@ export const TICK_PADDING_TOP = 5
 export const TICK_CHAR_WIDTH = 7
 export const TICK_CHAR_HEIGHT = 10
 
+export const AXIS_LABEL_PADDING_BOTTOM = 15
+
 export {Plot} from 'src/minard/components/Plot'
 
 export {
@@ -146,6 +148,8 @@ export interface PlotEnv {
   margins: Margins
   xTicks: number[]
   yTicks: number[]
+  xAxisLabel: string
+  yAxisLabel: string
 
   // If the domains have been explicitly passed in to the `Plot` component,
   // they will be stored here. Scales and child layers use the `xDomain` and

ui/src/minard/utils/plotEnvActions.ts

@@ -8,6 +8,8 @@ export type PlotAction =
   | ResetAction
   | SetControlledXDomainAction
   | SetControlledYDomainAction
+  | SetXAxisLabelAction
+  | SetYAxisLabelAction
 
 interface RegisterLayerAction {
   type: 'REGISTER_LAYER'
@@ -91,3 +93,23 @@ export const setControlledYDomain = (
   type: 'SET_CONTROLLED_Y_DOMAIN',
   payload: {yDomain},
 })
+
+interface SetXAxisLabelAction {
+  type: 'SET_X_AXIS_LABEL'
+  payload: {xAxisLabel: string}
+}
+
+export const setXAxisLabel = (xAxisLabel: string): SetXAxisLabelAction => ({
+  type: 'SET_X_AXIS_LABEL',
+  payload: {xAxisLabel},
+})
+
+interface SetYAxisLabelAction {
+  type: 'SET_Y_AXIS_LABEL'
+  payload: {yAxisLabel: string}
+}
+
+export const setYAxisLabel = (yAxisLabel: string): SetYAxisLabelAction => ({
+  type: 'SET_Y_AXIS_LABEL',
+  payload: {yAxisLabel},
+})

ui/src/minard/utils/plotEnvReducer.ts

@@ -13,6 +13,7 @@ import {
   TICK_CHAR_HEIGHT,
   TICK_PADDING_RIGHT,
   TICK_PADDING_TOP,
+  AXIS_LABEL_PADDING_BOTTOM,
 } from 'src/minard'
 import {PlotAction} from 'src/minard/utils/plotEnvActions'
 import {getGroupKey} from 'src/minard/utils/getGroupKey'
@@ -33,6 +34,8 @@ export const INITIAL_PLOT_ENV: PlotEnv = {
   },
   xTicks: [],
   yTicks: [],
+  xAxisLabel: '',
+  yAxisLabel: '',
   xDomain: null,
   yDomain: null,
   baseLayer: {
@@ -119,6 +122,26 @@ export const plotEnvReducer = (state: PlotEnv, action: PlotAction): PlotEnv =>
 
         return
       }
+
+      case 'SET_X_AXIS_LABEL': {
+        const {xAxisLabel} = action.payload
+
+        draftState.xAxisLabel = xAxisLabel
+
+        setLayout(draftState)
+
+        return
+      }
+
+      case 'SET_Y_AXIS_LABEL': {
+        const {yAxisLabel} = action.payload
+
+        draftState.yAxisLabel = yAxisLabel
+
+        setLayout(draftState)
+
+        return
+      }
     }
   })
 
@@ -230,11 +253,20 @@ const setLayout = (draftState: PlotEnv): void => {
   const yTickWidth =
     Math.max(...draftState.yTicks.map(t => String(t).length)) * TICK_CHAR_WIDTH
 
+  const xAxisLabelHeight = draftState.xAxisLabel
+    ? TICK_CHAR_HEIGHT + AXIS_LABEL_PADDING_BOTTOM
+    : 0
+
+  const yAxisLabelHeight = draftState.yAxisLabel
+    ? TICK_CHAR_HEIGHT + AXIS_LABEL_PADDING_BOTTOM
+    : 0
+
   const margins = {
     top: PLOT_PADDING,
     right: PLOT_PADDING,
-    bottom: TICK_CHAR_HEIGHT + TICK_PADDING_TOP + PLOT_PADDING,
+    bottom:
-    left: yTickWidth + TICK_PADDING_RIGHT + PLOT_PADDING,
+      TICK_CHAR_HEIGHT + TICK_PADDING_TOP + PLOT_PADDING + xAxisLabelHeight,
+    left: yTickWidth + TICK_PADDING_RIGHT + PLOT_PADDING + yAxisLabelHeight,
   }
 
   const innerWidth = width - margins.left - margins.right