feat(studio): add FlatSlider primitive for the flat inspector

packages/studio/src/components/editor/propertyPanelFlatPrimitives.test.tsx

@@ -7,6 +7,7 @@ import {
   FlatGroup,
   FlatRow,
   FlatSegmentedRow,
+  FlatSlider,
   PinnedZoneDivider,
 } from "./propertyPanelFlatPrimitives";
 
@@ -157,3 +158,71 @@ describe("PinnedZoneDivider", () => {
     act(() => root.unmount());
   });
 });
+
+describe("FlatSlider", () => {
+  it("renders the default tier with a dim knob at the correct position", () => {
+    const { host, root } = renderInto(
+      <FlatSlider
+        label="Layer blur"
+        value={0}
+        min={0}
+        max={40}
+        tier="default"
+        displayValue="0px"
+        onCommit={vi.fn()}
+      />,
+    );
+    const knob = host.querySelector<HTMLElement>('[data-flat-slider-knob="true"]');
+    expect(knob).not.toBeNull();
+    expect(knob?.className).toContain("bg-panel-text-4");
+    expect(knob?.style.left).toBe("0%");
+    const value = host.querySelector('[data-flat-slider-value="true"]');
+    expect(value?.className).toContain("text-panel-text-3");
+    expect(value?.textContent).toBe("0px");
+    act(() => root.unmount());
+  });
+
+  it("renders the explicitCustom tier with a filled track and bright knob", () => {
+    const { host, root } = renderInto(
+      <FlatSlider
+        label="Opacity"
+        value={100}
+        min={0}
+        max={100}
+        tier="explicitCustom"
+        displayValue="100%"
+        onCommit={vi.fn()}
+      />,
+    );
+    const fill = host.querySelector<HTMLElement>('[data-flat-slider-fill="true"]');
+    expect(fill?.style.width).toBe("100%");
+    const knob = host.querySelector<HTMLElement>('[data-flat-slider-knob="true"]');
+    expect(knob?.className).toContain("bg-white");
+    act(() => root.unmount());
+  });
+
+  it("commits a value on track click, proportional to click position", () => {
+    const onCommit = vi.fn();
+    const { host, root } = renderInto(
+      <FlatSlider
+        label="Opacity"
+        value={50}
+        min={0}
+        max={100}
+        tier="explicitCustom"
+        displayValue="50%"
+        onCommit={onCommit}
+      />,
+    );
+    const track = host.querySelector<HTMLElement>('[data-flat-slider-track="true"]');
+    if (!track) throw new Error("expected a track element");
+    Object.defineProperty(track, "getBoundingClientRect", {
+      value: () => ({ left: 0, width: 200, top: 0, height: 2, right: 200, bottom: 2 }),
+    });
+    act(() => {
+      track.dispatchEvent(new MouseEvent("pointerdown", { bubbles: true, clientX: 100 }));
+    });
+    expect(onCommit).toHaveBeenCalledWith(50);
+    act(() => root.unmount());
+  });
+});

packages/studio/src/components/editor/propertyPanelFlatPrimitives.tsx

@@ -233,3 +233,81 @@ export function PinnedZoneDivider() {
     </div>
   );
 }
+
+/* ------------------------------------------------------------------ */
+/*  FlatSlider — full-width label/track/value row                      */
+/* ------------------------------------------------------------------ */
+
+export function FlatSlider({
+  label,
+  value,
+  min,
+  max,
+  step = 1,
+  tier,
+  displayValue,
+  disabled,
+  onCommit,
+}: {
+  label: string;
+  value: number;
+  min: number;
+  max: number;
+  step?: number;
+  tier: "default" | "explicitCustom";
+  displayValue: string;
+  disabled?: boolean;
+  onCommit: (nextValue: number) => void;
+}) {
+  const clampedPct = Math.max(0, Math.min(100, ((value - min) / Math.max(max - min, 1e-6)) * 100));
+
+  const commitFromClientX = (clientX: number, rect: DOMRect) => {
+    const ratio = Math.max(0, Math.min(1, (clientX - rect.left) / Math.max(rect.width, 1)));
+    const raw = min + ratio * (max - min);
+    const stepped = Math.round(raw / step) * step;
+    onCommit(Math.max(min, Math.min(max, stepped)));
+  };
+
+  return (
+    <div className="flex min-h-[28px] items-center gap-2.5">
+      <span className="w-[86px] flex-shrink-0 text-[11px] text-panel-text-3">{label}</span>
+      <div
+        data-flat-slider-track="true"
+        role="slider"
+        aria-label={label}
+        aria-valuenow={value}
+        aria-disabled={disabled}
+        className={`relative h-0.5 flex-1 rounded-full bg-panel-hover ${
+          disabled ? "cursor-not-allowed" : "cursor-pointer"
+        }`}
+        onPointerDown={(e) => {
+          if (disabled) return;
+          commitFromClientX(e.clientX, e.currentTarget.getBoundingClientRect());
+        }}
+      >
+        {tier === "explicitCustom" && (
+          <div
+            data-flat-slider-fill="true"
+            className="absolute inset-y-0 left-0 rounded-full bg-panel-text-5"
+            style={{ width: `${clampedPct}%` }}
+          />
+        )}
+        <div
+          data-flat-slider-knob="true"
+          className={`absolute top-1/2 -translate-x-1/2 -translate-y-1/2 rounded-full ${
+            tier === "explicitCustom" ? "h-2 w-2 bg-white" : "h-[7px] w-[7px] bg-panel-text-4"
+          }`}
+          style={{ left: `${clampedPct}%` }}
+        />
+      </div>
+      <span
+        data-flat-slider-value="true"
+        className={`w-11 flex-shrink-0 text-right font-mono text-[10px] ${
+          tier === "explicitCustom" ? "text-panel-text-0" : "text-panel-text-3"
+        }`}
+      >
+        {displayValue}
+      </span>
+    </div>
+  );
+}