Added legend positioning for Chart

go/jsruntime/uikit/Chart.tsx

@@ -24,6 +24,30 @@ import { createMemo, createSignal, For, Show, onMount, onCleanup, JSXElement } f
 
 export type ChartKind = "line" | "area" | "bar" | "pie" | "donut";
 
+interface HorizontalLegend {
+    orientation: "horizontal";
+    position:
+        | "top-left"
+        | "top-center"
+        | "top-right"
+        | "bottom-left"
+        | "bottom-center"
+        | "bottom-right";
+}
+
+interface VerticalLegend {
+    orientation: "vertical";
+    position:
+        | "top-left"
+        | "center-left"
+        | "bottom-left"
+        | "top-right"
+        | "center-right"
+        | "bottom-right";
+}
+
+type ChartLegend = HorizontalLegend | VerticalLegend;
+
 export interface ChartSeries {
     name: string;
     data: number[];
@@ -67,7 +91,7 @@ export interface ChartProps {
     // Format a value for the value-axis ticks and the tooltip. Defaults to en-US grouping.
     valueFormat?: (v: number) => string;
 
-    legend?: boolean;  // default: true when there is more than one series (or a pie).
+    legend?: boolean | ChartLegend;  // default: true when there is more than one series (or a pie).
     grid?: boolean;    // cartesian only; default true.
     axes?: boolean;    // cartesian only; default true.
     tooltip?: boolean; // default true.
@@ -277,7 +301,28 @@ export function Chart(props: ChartProps): JSXElement {
     const colorOf = (i: number) =>
         props.series[i]?.color ?? props.palette?.[i % (props.palette.length || 1)] ?? CHART_TOKENS[i % CHART_TOKENS.length];
     const fmt = (v: number) => (props.valueFormat ?? defaultFormat)(v);
-    const showLegend = () => props.legend ?? (isRadial() || props.series.length > 1);
+
+    const legendVisible = () => {
+        if (props.legend === false) return false;
+        if (props.legend === true || props.legend === undefined) return isRadial() || props.series.length > 1;
+        return true; // an explicit ChartLegend object always shows the legend
+    };
+    // `true`/undefined carries no orientation or position — null tells the layout below to
+    // keep the original placement (a left-aligned wrapping row under the plot) untouched.
+    // Only a caller-supplied ChartLegend object turns on the orientation/position logic.
+    const legendConfig = (): ChartLegend | null =>
+        props.legend && typeof props.legend === "object" ? props.legend : null;
+    // Horizontal legends stack above/below the plot; vertical legends sit beside it.
+    const legendBefore = () => {
+        const cfg = legendConfig();
+        if (!cfg) return false; // default position is "after", matching the original layout
+        return cfg.orientation === "horizontal" ? cfg.position.startsWith("top") : cfg.position.endsWith("left");
+    };
+    const containerClass = () => {
+        const cfg = legendConfig();
+        if (!cfg) return "w-full";
+        return cfg.orientation === "vertical" ? "flex w-full items-stretch gap-4" : "flex flex-col w-full gap-3";
+    };
 
     // Clicking a legend key hides its series (cartesian) or slice (radial); the domain,
     // layout and marks recompute from what's left. A Set of the hidden indices — the index
@@ -290,23 +335,28 @@ export function Chart(props: ChartProps): JSXElement {
     });
 
     return (
-        <div ref={wrap} class={"w-full" + (props.class ? " " + props.class : "")}>
+        <div class={"w-full" + (props.class ? " " + props.class : "")}>
             <Show when={props.title}>
                 <div class="mb-2 text-center text-sm font-medium text-ink">{props.title}</div>
             </Show>
+            <div class={containerClass()}>
+                <Show when={legendVisible() && legendBefore()}>
+                    <Legend props={props} legend={legendConfig()} colorOf={colorOf} hidden={hidden()} onToggle={toggle} />
+                </Show>
                 {/* the plot + its absolutely-positioned tooltip share this relative box, so the
                     tooltip's pointer coordinates aren't thrown off by a title or legend outside it. */}
-            <div class="relative w-full">
+                <div ref={wrap} class="relative w-full min-w-0">
                     <Show when={isRadial()} fallback={
                         <CartesianChart props={props} width={width()} height={height()} colorOf={colorOf} fmt={fmt} hidden={hidden} />
                     }>
                         <RadialChart props={props} width={width()} height={height()} colorOf={colorOf} fmt={fmt} hidden={hidden} />
                     </Show>
                 </div>
-            <Show when={showLegend()}>
+                <Show when={legendVisible() && !legendBefore()}>
-                <Legend props={props} colorOf={colorOf} hidden={hidden()} onToggle={toggle} />
+                    <Legend props={props} legend={legendConfig()} colorOf={colorOf} hidden={hidden()} onToggle={toggle} />
                 </Show>
             </div>
+        </div>
     );
 }
 
@@ -757,7 +807,7 @@ function RadialChart(p: SubProps): JSXElement {
 
 // ── legend ─────────────────────────────────────────────────────────────────────
 
-function Legend(p: { props: ChartProps; colorOf: (i: number) => string; hidden: Set<number>; onToggle: (i: number) => void }): JSXElement {
+function Legend(p: { props: ChartProps; legend: ChartLegend | null; colorOf: (i: number) => string; hidden: Set<number>; onToggle: (i: number) => void }): JSXElement {
     // Pie/donut identity is the SLICE; cartesian identity is the SERIES. A line keys with
     // a short stroke, a fill (bar/area/slice) with a swatch — the legend mirrors the mark.
     // Each key is a button: click it to toggle that series/slice, which greys the key and
@@ -767,8 +817,25 @@ function Legend(p: { props: ChartProps; colorOf: (i: number) => string; hidden:
     const items = () => isRadial
         ? (p.props.labels ?? p.props.series[0]?.data.map((_, i) => String(i + 1)) ?? []).map((name, i) => ({ name, i }))
         : p.props.series.map((s, i) => ({ name: s.name, i }));
+
+    // No legend config (bare `true`/default): the original layout — a left-aligned wrapping
+    // row under the plot. An explicit ChartLegend picks the row/column axis (orientation)
+    // and where along it the legend sits (position).
+    const containerClass = () => {
+        const cfg = p.legend;
+        if (!cfg) return "mt-3 flex flex-wrap items-center gap-x-4 gap-y-1.5";
+        if (cfg.orientation === "vertical") {
+            const justify = cfg.position.startsWith("top") ? "justify-start"
+                : cfg.position.startsWith("bottom") ? "justify-end" : "justify-center";
+            return `flex flex-col ${justify} gap-1.5 shrink-0`;
+        }
+        const justify = cfg.position.endsWith("left") ? "justify-start"
+            : cfg.position.endsWith("right") ? "justify-end" : "justify-center";
+        return `flex flex-wrap items-center gap-x-4 gap-y-1.5 ${justify}`;
+    };
+
     return (
-        <div class="mt-3 flex flex-wrap items-center gap-x-4 gap-y-1.5">
+        <div class={containerClass()}>
             <For each={items()}>{(it) => {
                 const off = () => p.hidden.has(it.i);
                 return (