✨ (a11y) make time slider keyboard accessible

packages/@ourworldindata/grapher/src/controls/ActionButtons.tsx

@@ -347,6 +347,7 @@ export function ActionButton(props: {
                 onMouseLeave={(): void => {
                     setShowTooltip(false)
                 }}
+                aria-label={props.label}
             >
                 <FontAwesomeIcon icon={props.icon} />
                 {props.showLabel && (

packages/@ourworldindata/grapher/src/controls/ContentSwitchers.scss

@@ -24,7 +24,7 @@
         position: relative;
     }
 
-    li > a {
+    li > button {
         $height: $controlRowHeight - 2 * $visual-gap;
 
         display: block;
@@ -69,7 +69,7 @@
         }
     }
 
-    li.active > a {
+    li.active > button {
         color: $active-text;
         background-color: $active-fill;
 
@@ -105,7 +105,7 @@
 }
 
 &.GrapherComponentMedium {
-    .ContentSwitchers:not(.iconOnly) li > a {
+    .ContentSwitchers:not(.iconOnly) li > button {
         padding: 0 8px;
     }
 }

packages/@ourworldindata/grapher/src/controls/ContentSwitchers.tsx

@@ -80,19 +80,20 @@ function Tab(props: {
     tab: GrapherTabOption
     icon: JSX.Element
     isActive?: boolean
-    onClick?: React.MouseEventHandler<HTMLAnchorElement>
+    onClick?: React.MouseEventHandler<HTMLButtonElement>
     showLabel?: boolean
 }): JSX.Element {
     const className = "tab clickable" + (props.isActive ? " active" : "")
     return (
         <li key={props.tab} className={className}>
-            <a
+            <button
                 onClick={props.onClick}
                 data-track-note={"chart_click_" + props.tab}
+                aria-label={props.tab}
             >
                 {props.icon}
                 {props.showLabel && <span className="label">{props.tab}</span>}
-            </a>
+            </button>
         </li>
     )
 }

packages/@ourworldindata/grapher/src/controls/EntitySelectionToggle.tsx

@@ -82,6 +82,7 @@ export class EntitySelectionToggle extends React.Component<{
                         e.stopPropagation()
                     }}
                     data-track-note="chart_add_entity"
+                    aria-label={`${label.action} ${label.entity}`}
                 >
                     {label.icon}
                     <label>

packages/@ourworldindata/grapher/src/controls/SettingsMenu.tsx

@@ -421,6 +421,7 @@ export class SettingsMenu extends React.Component<{
                     onClick={this.toggleVisibility}
                     data-track-note="chart_settings_menu_toggle"
                     title="Chart settings"
+                    aria-label="Chart settings"
                 >
                     <FontAwesomeIcon icon={faGear} />
                     <span className="label"> Settings</span>

packages/@ourworldindata/grapher/src/timeline/TimelineComponent.tsx

@@ -258,7 +258,7 @@ export class TimelineComponent extends React.Component<{
         const time =
             markerType === "start" ? controller.minTime : controller.maxTime
         return (
-            <div
+            <button
                 className="date clickable"
                 onClick={(): void =>
                     markerType === "start"
@@ -267,7 +267,7 @@ export class TimelineComponent extends React.Component<{
                 }
             >
                 {this.formatTime(time)}
-            </div>
+            </button>
         )
     }
 
@@ -279,6 +279,32 @@ export class TimelineComponent extends React.Component<{
         this.controller.togglePlay()
     }
 
+    @action.bound updateStartTimeOnKeyDown(key: string): void {
+        const { controller } = this
+        if (key === "Home") {
+            controller.resetStartToMin()
+        } else if (key === "End") {
+            controller.setStartToMax()
+        } else if (key === "ArrowLeft" || key === "ArrowDown") {
+            controller.decreaseStartTime()
+        } else if (key === "ArrowRight" || key === "ArrowUp") {
+            controller.increaseStartTime()
+        }
+    }
+
+    @action.bound updateEndTimeOnKeyDown(key: string): void {
+        const { controller } = this
+        if (key === "Home") {
+            controller.setEndToMin()
+        } else if (key === "End") {
+            controller.resetEndToMax()
+        } else if (key === "ArrowLeft" || key === "ArrowDown") {
+            controller.decreaseEndTime()
+        } else if (key === "ArrowRight" || key === "ArrowUp") {
+            controller.increaseEndTime()
+        }
+    }
+
     convertToTime(time: number): number {
         if (time === -Infinity) return this.controller.minTime
         if (time === +Infinity) return this.controller.maxTime
@@ -291,6 +317,8 @@ export class TimelineComponent extends React.Component<{
             controller
         const { startHandleTimeBound, endHandleTimeBound } = manager
 
+        const formattedMinTime = this.formatTime(minTime)
+        const formattedMaxTime = this.formatTime(maxTime)
         const formattedStartTime = this.formatTime(
             timeFromTimebounds(startHandleTimeBound, minTime, maxTime)
         )
@@ -337,12 +365,29 @@ export class TimelineComponent extends React.Component<{
                 >
                     <TimelineHandle
                         type="startMarker"
+                        label="Start time"
                         offsetPercent={startTimeProgress * 100}
-                        tooltipContent={formattedStartTime}
+                        formattedMinTime={formattedMinTime}
+                        formattedMaxTime={formattedMaxTime}
+                        formattedCurrTime={formattedStartTime}
                         tooltipVisible={this.startTooltipVisible}
                         tooltipZIndex={
                             this.lastUpdatedTooltip === "startMarker" ? 2 : 1
                         }
+                        onKeyDown={action((e) => {
+                            // prevent browser to scroll to the top or bottom of the page
+                            if (e.key === "Home" || e.key === "End")
+                                e.preventDefault()
+
+                            this.updateStartTimeOnKeyDown(e.key)
+                        })}
+                        onFocus={action(() => {
+                            this.showTooltips()
+                        })}
+                        onBlur={action(() => {
+                            this.startTooltipVisible = false
+                            this.endTooltipVisible = false
+                        })}
                     />
                     <div
                         className="interval"
@@ -353,12 +398,29 @@ export class TimelineComponent extends React.Component<{
                     />
                     <TimelineHandle
                         type="endMarker"
+                        label="End time"
                         offsetPercent={endTimeProgress * 100}
-                        tooltipContent={formattedEndTime}
+                        formattedMinTime={formattedMinTime}
+                        formattedMaxTime={formattedMaxTime}
+                        formattedCurrTime={formattedEndTime}
                         tooltipVisible={this.endTooltipVisible}
                         tooltipZIndex={
                             this.lastUpdatedTooltip === "endMarker" ? 2 : 1
                         }
+                        onKeyDown={action((e) => {
+                            // prevent browser to scroll to the top or bottom of the page
+                            if (e.key === "Home" || e.key === "End")
+                                e.preventDefault()
+
+                            this.updateEndTimeOnKeyDown(e.key)
+                        })}
+                        onFocus={action(() => {
+                            this.showTooltips()
+                        })}
+                        onBlur={action(() => {
+                            this.startTooltipVisible = false
+                            this.endTooltipVisible = false
+                        })}
                     />
                 </div>
                 {this.timelineEdgeMarker("end")}
@@ -369,23 +431,45 @@ export class TimelineComponent extends React.Component<{
 
 const TimelineHandle = ({
     type,
+    label,
     offsetPercent,
-    tooltipContent,
+    formattedMinTime,
+    formattedMaxTime,
+    formattedCurrTime,
     tooltipVisible,
     tooltipZIndex,
+    onKeyDown,
+    onFocus,
+    onBlur,
 }: {
     type: "startMarker" | "endMarker"
+    label: string
     offsetPercent: number
-    tooltipContent: string
+    formattedMinTime: string
+    formattedMaxTime: string
+    formattedCurrTime: string
     tooltipVisible: boolean
     tooltipZIndex: number
+    onKeyDown?: React.KeyboardEventHandler<HTMLDivElement>
+    onFocus?: React.FocusEventHandler<HTMLDivElement>
+    onBlur?: React.FocusEventHandler<HTMLDivElement>
 }): JSX.Element => {
     return (
+        // @ts-expect-error aria-value* fields expect a number, but we're passing a string
         <div
             className={classNames("handle", type)}
             style={{
                 left: `${offsetPercent}%`,
             }}
+            role="slider"
+            tabIndex={0}
+            aria-valuemin={formattedMinTime}
+            aria-valuenow={formattedCurrTime}
+            aria-valuemax={formattedMaxTime}
+            aria-label={label}
+            onFocus={onFocus}
+            onBlur={onBlur}
+            onKeyDown={onKeyDown}
         >
             <div className="icon" />
             {tooltipVisible && (
@@ -398,7 +482,7 @@ const TimelineHandle = ({
                         className="handle-label"
                         style={{ zIndex: tooltipZIndex }}
                     >
-                        {tooltipContent}
+                        {formattedCurrTime}
                     </div>
                 </>
             )}

packages/@ourworldindata/grapher/src/timeline/TimelineController.ts

@@ -65,6 +65,10 @@ export class TimelineController {
         return this.timesAsc[this.timesAsc.indexOf(time) + 1] ?? this.maxTime
     }
 
+    getPrevTime(time: number): number {
+        return this.timesAsc[this.timesAsc.indexOf(time) - 1] ?? this.minTime
+    }
+
     // By default, play means extend the endTime to the right. Toggle this to play one time unit at a time.
     private rangeMode = true
     toggleRangeMode(): this {
@@ -111,6 +115,26 @@ export class TimelineController {
         return tickCount
     }
 
+    increaseStartTime(): void {
+        const nextTime = this.getNextTime(this.startTime)
+        this.updateStartTime(nextTime)
+    }
+
+    decreaseStartTime(): void {
+        const prevTime = this.getPrevTime(this.startTime)
+        this.updateStartTime(prevTime)
+    }
+
+    increaseEndTime(): void {
+        const nextTime = this.getNextTime(this.endTime)
+        this.updateEndTime(nextTime)
+    }
+
+    decreaseEndTime(): void {
+        const prevTime = this.getPrevTime(this.endTime)
+        this.updateEndTime(prevTime)
+    }
+
     private stop(): void {
         this.manager.isPlaying = false
     }
@@ -215,4 +239,12 @@ export class TimelineController {
     resetEndToMax(): void {
         this.updateEndTime(TimeBoundValue.positiveInfinity)
     }
+
+    setStartToMax(): void {
+        this.updateStartTime(TimeBoundValue.positiveInfinity)
+    }
+
+    setEndToMin(): void {
+        this.updateEndTime(TimeBoundValue.negativeInfinity)
+    }
 }