feat(studio): scale GSAP positions on clip resize + shift on drag + diamond fixes (#1448)

Resize: proportionally scale all GSAP animation positions and durations
to fit the new clip duration via scalePositionsInScript. This preserves
clip-relative keyframe percentages — diamonds don't move during resize,
nothing disappears. Modeled after After Effects Time Stretch behavior.

Drag: shift all GSAP positions by the time delta (unchanged from before).

Diamond rendering:
- Clamp diamonds at 0%/100% so they stay fully visible at clip edges
- Filter out-of-range keyframes using predicted percentages during resize
- Clamp connection lines to clip boundaries
- PropertyRows: same edge clamping for SVG diamonds

Parser: scalePositionsInScript (proportional position + duration scaling),
shiftPositionsInScript (rigid shift), scale-positions + shift-positions
mutation types, 5 shift tests passing.

packages/core/src/parsers/gsapParser.test.ts

@@ -19,6 +19,8 @@ import {
   addAnimationWithKeyframesToScript,
   splitAnimationsInScript,
   splitIntoPropertyGroups,
+  shiftPositionsInScript,
+  scalePositionsInScript,
 } from "./gsapParser.js";
 import type { GsapAnimation } from "./gsapParser.js";
 import { classifyPropertyGroup, classifyTweenPropertyGroup } from "./gsapConstants.js";
@@ -2275,3 +2277,113 @@ describe("splitIntoPropertyGroups", () => {
     }
   });
 });
+
+describe("shiftPositionsInScript", () => {
+  it("shifts all numeric positions for the target selector", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.from("#hero", { opacity: 0, duration: 1 }, 0);
+tl.to("#hero", { opacity: 0, duration: 0.5 }, 2.5);
+tl.from("#bg", { scale: 0, duration: 1 }, 1);`;
+    const result = shiftPositionsInScript(script, "#hero", 3);
+    const parsed = parseGsapScript(result);
+    const hero = parsed.animations.filter((a) => a.targetSelector === "#hero");
+    expect(hero[0].position).toBe(3);
+    expect(hero[1].position).toBe(5.5);
+    const bg = parsed.animations.find((a) => a.targetSelector === "#bg");
+    expect(bg!.position).toBe(1);
+  });
+
+  it("clamps negative-going positions to zero", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.to("#el", { x: 100, duration: 1 }, 0.3);
+tl.to("#el", { y: 50, duration: 1 }, 1.5);`;
+    const result = shiftPositionsInScript(script, "#el", -1.0);
+    const parsed = parseGsapScript(result);
+    const anims = parsed.animations.filter((a) => a.targetSelector === "#el");
+    expect(anims[0].position).toBe(0);
+    expect(anims[1].position).toBe(0.5);
+  });
+
+  it("returns the original script when delta is zero", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.to("#el", { x: 100, duration: 1 }, 2);`;
+    expect(shiftPositionsInScript(script, "#el", 0)).toBe(script);
+  });
+
+  it("does not collide when two tweens have adjacent positions", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.to("#burst", { opacity: 1, duration: 0.5 }, 1.0);
+tl.to("#burst", { opacity: 0, duration: 0.5 }, 1.5);`;
+    const result = shiftPositionsInScript(script, "#burst", 0.5);
+    const parsed = parseGsapScript(result);
+    const burst = parsed.animations.filter((a) => a.targetSelector === "#burst");
+    expect(burst[0].position).toBe(1.5);
+    expect(burst[1].position).toBe(2);
+  });
+
+  it("skips string positions", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.to("#el", { x: 100, duration: 1 }, 2);
+tl.to("#el", { y: 50, duration: 1 }, "+=0.5");`;
+    const result = shiftPositionsInScript(script, "#el", 1);
+    const parsed = parseGsapScript(result);
+    expect(parsed.animations[0].position).toBe(3);
+    expect(parsed.animations[1].position).toBe("+=0.5");
+  });
+});
+
+describe("scalePositionsInScript", () => {
+  it("scales positions and durations proportionally for the target selector", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.from("#hero", { opacity: 0, duration: 1 }, 0);
+tl.to("#hero", { opacity: 0, duration: 0.5 }, 2.5);
+tl.from("#bg", { scale: 0, duration: 1 }, 1);`;
+    const result = scalePositionsInScript(script, "#hero", 0, 3, 0, 2);
+    const parsed = parseGsapScript(result);
+    const hero = parsed.animations.filter((a) => a.targetSelector === "#hero");
+    expect(hero[0].position).toBe(0);
+    expect(hero[0].duration).toBeCloseTo(0.667, 2);
+    expect(hero[1].position).toBeCloseTo(1.667, 2);
+    expect(hero[1].duration).toBeCloseTo(0.333, 2);
+    const bg = parsed.animations.find((a) => a.targetSelector === "#bg");
+    expect(bg!.position).toBe(1);
+    expect(bg!.duration).toBe(1);
+  });
+
+  it("handles start-edge resize (new start + shorter duration)", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.from("#el", { opacity: 0, duration: 1 }, 0);
+tl.to("#el", { y: 50, duration: 0.5 }, 2.5);`;
+    const result = scalePositionsInScript(script, "#el", 0, 3, 1, 2);
+    const parsed = parseGsapScript(result);
+    const anims = parsed.animations.filter((a) => a.targetSelector === "#el");
+    expect(anims[0].position).toBe(1);
+    expect(anims[0].duration).toBeCloseTo(0.667, 2);
+    expect(anims[1].position).toBeCloseTo(2.667, 2);
+    expect(anims[1].duration).toBeCloseTo(0.333, 2);
+  });
+
+  it("clamps negative-going positions to zero", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.to("#el", { x: 100, duration: 1 }, 2);`;
+    const result = scalePositionsInScript(script, "#el", 2, 1, 0, 0.5);
+    const parsed = parseGsapScript(result);
+    expect(parsed.animations[0].position).toBe(0);
+  });
+
+  it("returns the original script when old and new timing are identical", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.to("#el", { x: 100, duration: 1 }, 2);`;
+    expect(scalePositionsInScript(script, "#el", 0, 3, 0, 3)).toBe(script);
+  });
+
+  it("skips string positions", () => {
+    const script = `const tl = gsap.timeline({ paused: true });
+tl.to("#el", { x: 100, duration: 1 }, 2);
+tl.to("#el", { y: 50, duration: 1 }, "+=0.5");`;
+    const result = scalePositionsInScript(script, "#el", 0, 3, 0, 2);
+    const parsed = parseGsapScript(result);
+    expect(parsed.animations[0].position).toBeCloseTo(1.333, 2);
+    expect(parsed.animations[1].position).toBe("+=0.5");
+  });
+});

packages/core/src/parsers/gsapParser.ts

@@ -1322,6 +1322,67 @@ export function updateAnimationInScript(
   return recast.print(parsed.ast).code;
 }
 
+export function shiftPositionsInScript(
+  script: string,
+  targetSelector: string,
+  delta: number,
+): string {
+  let parsed: ParsedGsapAst;
+  try {
+    parsed = parseGsapAst(script);
+  } catch (e) {
+    console.warn("[gsap-parser] shiftPositionsInScript parse failed:", e);
+    return script;
+  }
+  let changed = false;
+  for (const entry of parsed.located) {
+    if (entry.animation.targetSelector !== targetSelector) continue;
+    if (typeof entry.animation.position !== "number") continue;
+    const newPos = Math.max(0, Math.round((entry.animation.position + delta) * 1000) / 1000);
+    applyUpdatesToCall(entry.call, { position: newPos });
+    changed = true;
+  }
+  return changed ? recast.print(parsed.ast).code : script;
+}
+
+export function scalePositionsInScript(
+  script: string,
+  targetSelector: string,
+  oldStart: number,
+  oldDuration: number,
+  newStart: number,
+  newDuration: number,
+): string {
+  if (oldDuration <= 0 || newDuration <= 0) return script;
+  const ratio = newDuration / oldDuration;
+  let parsed: ParsedGsapAst;
+  try {
+    parsed = parseGsapAst(script);
+  } catch (e) {
+    console.warn("[gsap-parser] scalePositionsInScript parse failed:", e);
+    return script;
+  }
+  let changed = false;
+  for (const entry of parsed.located) {
+    if (entry.animation.targetSelector !== targetSelector) continue;
+    if (typeof entry.animation.position !== "number") continue;
+    const newPos = Math.max(
+      0,
+      Math.round((newStart + (entry.animation.position - oldStart) * ratio) * 1000) / 1000,
+    );
+    const updates: Partial<GsapAnimation> = { position: newPos };
+    if (typeof entry.animation.duration === "number" && entry.animation.duration > 0) {
+      updates.duration = Math.max(
+        0.001,
+        Math.round(entry.animation.duration * ratio * 1000) / 1000,
+      );
+    }
+    applyUpdatesToCall(entry.call, updates);
+    changed = true;
+  }
+  return changed ? recast.print(parsed.ast).code : script;
+}
+
 function updateAnimationSelector(script: string, animationId: string, newSelector: string): string {
   let parsed: ParsedGsapAst;
   try {

packages/core/src/studio-api/routes/files.ts

@@ -466,6 +466,19 @@ type GsapMutationRequest =
   | {
       type: "delete-all-for-selector";
       targetSelector: string;
+    }
+  | {
+      type: "shift-positions";
+      targetSelector: string;
+      delta: number;
+    }
+  | {
+      type: "scale-positions";
+      targetSelector: string;
+      oldStart: number;
+      oldDuration: number;
+      newStart: number;
+      newDuration: number;
     };
 
 // ── GSAP mutation executor ──────────────────────────────────────────────────
@@ -715,6 +728,35 @@ async function executeGsapMutation(
       const result = splitIntoPropertyGroups(block.scriptText, body.animationId);
       return result.script;
     }
+    case "shift-positions": {
+      const { targetSelector, delta } = body;
+      if (!targetSelector || !Number.isFinite(delta) || delta === 0) return block.scriptText;
+      const { shiftPositionsInScript } = parser;
+      return shiftPositionsInScript(block.scriptText, targetSelector, delta);
+    }
+    case "scale-positions": {
+      const { targetSelector, oldStart, oldDuration, newStart, newDuration } = body;
+      if (
+        !targetSelector ||
+        !Number.isFinite(oldStart) ||
+        !Number.isFinite(oldDuration) ||
+        !Number.isFinite(newStart) ||
+        !Number.isFinite(newDuration) ||
+        oldDuration <= 0 ||
+        newDuration <= 0
+      )
+        return block.scriptText;
+      if (oldStart === newStart && oldDuration === newDuration) return block.scriptText;
+      const { scalePositionsInScript } = parser;
+      return scalePositionsInScript(
+        block.scriptText,
+        targetSelector,
+        oldStart,
+        oldDuration,
+        newStart,
+        newDuration,
+      );
+    }
     default:
       return respond({ error: `unknown mutation type: ${(body as { type: string }).type}` }, 400);
   }

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

@@ -6,7 +6,7 @@ interface GestureTrailOverlayProps {
   sampleCount?: number;
   trail?: Array<{ x: number; y: number }>;
   simplifiedPoints?: Map<number, Record<string, number>>;
-  canvasRect: { left: number; top: number; width: number; height: number };
+  canvasRect: { left: number; top: number; width: number; height: number } | null;
   compositionSize?: { width: number; height: number };
   mode: "recording" | "preview";
   accentColor?: string;
@@ -23,6 +23,7 @@ export const GestureTrailOverlay = memo(function GestureTrailOverlay({
   accentColor = "#3CE6AC",
 }: GestureTrailOverlayProps) {
   const trailPoints = useMemo(() => {
+    if (!canvasRect) return "";
     if (trail && trail.length > 1) {
       return trail.map((p) => `${p.x - canvasRect.left},${p.y - canvasRect.top}`).join(" ");
     }
@@ -32,7 +33,7 @@ export const GestureTrailOverlay = memo(function GestureTrailOverlay({
       .map((s) => `${s.properties.x},${s.properties.y}`)
       .join(" ");
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [samples, trail, sampleCount, canvasRect.left, canvasRect.top]);
+  }, [samples, trail, sampleCount, canvasRect?.left, canvasRect?.top]);
 
   const simplifiedPath = useMemo(() => {
     if (!simplifiedPoints || simplifiedPoints.size === 0) return "";
@@ -58,7 +59,7 @@ export const GestureTrailOverlay = memo(function GestureTrailOverlay({
     return pts.sort((a, b) => a.pct - b.pct);
   }, [simplifiedPoints]);
 
-  if (samples.length < 2 && !simplifiedPoints) return null;
+  if (!canvasRect || (samples.length < 2 && !simplifiedPoints)) return null;
 
   return (
     <svg

packages/studio/src/hooks/timelineEditingHelpers.ts

@@ -144,5 +144,66 @@ export async function readFileContent(projectId: string, targetPath: string): Pr
   return data.content;
 }
 
+/**
+ * Shift all GSAP animation positions targeting a given element by a time delta.
+ * Calls the server-side GSAP mutation endpoint which uses the AST-based parser.
+ */
+export async function shiftGsapPositions(
+  projectId: string,
+  filePath: string,
+  elementId: string,
+  delta: number,
+): Promise<void> {
+  if (delta === 0 || !elementId) return;
+  const res = await fetch(
+    `/api/projects/${projectId}/gsap-mutations/${encodeURIComponent(filePath)}`,
+    {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({
+        type: "shift-positions",
+        targetSelector: `#${elementId}`,
+        delta,
+      }),
+    },
+  );
+  if (!res.ok) {
+    const err = await res.json().catch(() => null);
+    throw new Error((err as { error?: string })?.error ?? "shift-positions failed");
+  }
+}
+
+export async function scaleGsapPositions(
+  projectId: string,
+  filePath: string,
+  elementId: string,
+  oldStart: number,
+  oldDuration: number,
+  newStart: number,
+  newDuration: number,
+): Promise<void> {
+  if (!elementId || oldDuration <= 0 || newDuration <= 0) return;
+  if (oldStart === newStart && oldDuration === newDuration) return;
+  const res = await fetch(
+    `/api/projects/${projectId}/gsap-mutations/${encodeURIComponent(filePath)}`,
+    {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({
+        type: "scale-positions",
+        targetSelector: `#${elementId}`,
+        oldStart,
+        oldDuration,
+        newStart,
+        newDuration,
+      }),
+    },
+  );
+  if (!res.ok) {
+    const err = await res.json().catch(() => null);
+    throw new Error((err as { error?: string })?.error ?? "scale-positions failed");
+  }
+}
+
 // Re-export applyPatchByTarget for use in the hook (avoids double import in callers)
 export { applyPatchByTarget, formatTimelineAttributeNumber };

packages/studio/src/hooks/useTimelineEditing.ts

@@ -26,6 +26,8 @@ import {
   readFileContent,
   applyPatchByTarget,
   formatTimelineAttributeNumber,
+  shiftGsapPositions,
+  scaleGsapPositions,
 } from "./timelineEditingHelpers";
 import type { PersistTimelineEditInput } from "./timelineEditingHelpers";
 
@@ -122,6 +124,8 @@ export function useTimelineEditing({
         ["data-start", formatTimelineAttributeNumber(updates.start)],
         ["data-track-index", String(updates.track)],
       ]);
+      const delta = updates.start - element.start;
+      const filePath = element.sourceFile || activeCompPath || "index.html";
       return enqueueEdit(element, "Move timeline clip", (original, target) => {
         let patched = applyPatchByTarget(original, target, {
           type: "attribute",
@@ -133,9 +137,16 @@ export function useTimelineEditing({
           property: "track-index",
           value: String(updates.track),
         });
+      }).then(() => {
+        const pid = projectIdRef.current;
+        if (delta !== 0 && element.domId && pid) {
+          return shiftGsapPositions(pid, filePath, element.domId, delta)
+            .then(() => reloadPreview())
+            .catch((err) => console.error("[Timeline] Failed to shift GSAP positions", err));
+        }
       });
     },
-    [previewIframeRef, enqueueEdit],
+    [previewIframeRef, enqueueEdit, activeCompPath, reloadPreview],
   );
 
   const handleTimelineElementResize = useCallback(
@@ -147,9 +158,6 @@ export function useTimelineEditing({
         ["data-start", formatTimelineAttributeNumber(updates.start)],
         ["data-duration", formatTimelineAttributeNumber(updates.duration)],
       ];
-      // A start-edge trim advances the media-start offset (skips into the
-      // source). Patch it live too — otherwise the iframe keeps the old offset
-      // and the clip only repositions instead of trimming the audio.
       if (updates.playbackStart != null) {
         const liveAttr =
           element.playbackStartAttr === "playback-start"
@@ -158,6 +166,9 @@ export function useTimelineEditing({
         liveAttrs.push([liveAttr, formatTimelineAttributeNumber(updates.playbackStart)]);
       }
       patchIframeDomTiming(previewIframeRef.current, element, liveAttrs);
+      const filePath = element.sourceFile || activeCompPath || "index.html";
+      const timingChanged =
+        updates.start !== element.start || updates.duration !== element.duration;
       return enqueueEdit(element, "Resize timeline clip", (original, target) => {
         const pbs = resolveResizePlaybackStart(original, target, element, updates);
         let patched = applyPatchByTarget(original, target, {
@@ -178,9 +189,25 @@ export function useTimelineEditing({
           });
         }
         return patched;
+      }).then(() => {
+        const pid = projectIdRef.current;
+        if (timingChanged && element.domId && pid) {
+          return scaleGsapPositions(
+            pid,
+            filePath,
+            element.domId,
+            element.start,
+            element.duration,
+            updates.start,
+            updates.duration,
+          )
+            .then(() => reloadPreview())
+            .catch((err) => console.error("[Timeline] Failed to scale GSAP positions", err));
+        }
+        return reloadPreview();
       });
     },
-    [previewIframeRef, enqueueEdit],
+    [previewIframeRef, enqueueEdit, activeCompPath, reloadPreview],
   );
 
   const handleTimelineElementDelete = useCallback(

packages/studio/src/player/components/TimelineClipDiamonds.tsx

@@ -40,6 +40,15 @@ interface TimelineClipDiamondsProps {
 }
 
 const DIAMOND_RATIO = 0.8;
+// Percentage tolerance for rendering keyframes near clip boundaries. Keyframes
+// slightly outside [0, 100] (from rounding or stale cache during the async
+// persist → reload cycle) are clamped to the clip edge rather than hidden.
+export const KF_MIN_PCT = -5;
+export const KF_MAX_PCT = 105;
+
+function clampDiamondLeft(rawLeft: number, diamondSize: number, clipWidth: number): number {
+  return Math.max(0, Math.min(clipWidth - diamondSize, rawLeft));
+}
 
 export const TimelineClipDiamonds = memo(function TimelineClipDiamonds({
   keyframesData,
@@ -108,7 +117,9 @@ export const TimelineClipDiamonds = memo(function TimelineClipDiamonds({
   const diamondSize = Math.round(clipHeightPx * (beatsActive ? 0.45 : DIAMOND_RATIO));
   const half = diamondSize / 2;
   const centerY = beatsActive ? BEAT_BAND_H + (clipHeightPx - BEAT_BAND_H) / 2 : clipHeightPx / 2;
-  const sorted = keyframesData.keyframes.slice().sort((a, b) => a.percentage - b.percentage);
+  const sorted = keyframesData.keyframes
+    .filter((kf) => kf.percentage >= KF_MIN_PCT && kf.percentage <= KF_MAX_PCT)
+    .sort((a, b) => a.percentage - b.percentage);
   const baseColor = isSelected ? accentColor : "#a3a3a3";
   const baseOpacity = isSelected ? 0.4 : 0.25;
 
@@ -182,7 +193,6 @@ export const TimelineClipDiamonds = memo(function TimelineClipDiamonds({
     document.addEventListener("pointerup", handleUp);
   };
 
-  // Effective % for rendering: the dragged keyframe follows the (snapped) cursor.
   const effPct = (p: number): number => (drag && drag.origPct === p ? drag.pct : p);
 
   return (
@@ -190,8 +200,12 @@ export const TimelineClipDiamonds = memo(function TimelineClipDiamonds({
       {sorted.map((kf, i) => {
         if (i === 0) return null;
         const prev = sorted[i - 1]!;
-        const x1 = (effPct(prev.percentage) / 100) * clipWidthPx;
+        const x1 = Math.max(
-        const x2 = (effPct(kf.percentage) / 100) * clipWidthPx;
+          0,
+          Math.min(clipWidthPx, (effPct(prev.percentage) / 100) * clipWidthPx),
+        );
+        const x2 = Math.max(0, Math.min(clipWidthPx, (effPct(kf.percentage) / 100) * clipWidthPx));
+        if (x2 - x1 < 1) return null;
         return (
           <div
             key={`line-${i}-${prev.percentage}-${kf.percentage}`}
@@ -211,7 +225,11 @@ export const TimelineClipDiamonds = memo(function TimelineClipDiamonds({
       })}
 
       {sorted.map((kf, i) => {
-        const leftPx = (effPct(kf.percentage) / 100) * clipWidthPx - half;
+        const leftPx = clampDiamondLeft(
+          (effPct(kf.percentage) / 100) * clipWidthPx - half,
+          diamondSize,
+          clipWidthPx,
+        );
         const kfKey = `${elementId}:${kf.percentage}`;
         const isKfSelected = selectedKeyframes.has(kfKey);
         const atPlayhead = isSelected && Math.abs(kf.percentage - currentPercentage) < 0.5;

packages/studio/src/player/components/TimelinePropertyRows.tsx

@@ -1,5 +1,6 @@
 import { memo } from "react";
 import type { KeyframeCacheEntry } from "../store/playerStore";
+import { KF_MIN_PCT, KF_MAX_PCT } from "./TimelineClipDiamonds";
 
 const SUB_TRACK_H = 24;
 const DIAMOND_SIZE = 6;
@@ -44,7 +45,9 @@ export const TimelinePropertyRows = memo(function TimelinePropertyRows({
   return (
     <div className="flex flex-col">
       {properties.map((prop) => {
-        const propKeyframes = keyframesData.keyframes.filter((kf) => prop in kf.properties);
+        const propKeyframes = keyframesData.keyframes
+          .filter((kf) => prop in kf.properties)
+          .filter((kf) => kf.percentage >= KF_MIN_PCT && kf.percentage <= KF_MAX_PCT);
         if (propKeyframes.length === 0) return null;
 
         return (
@@ -67,7 +70,10 @@ export const TimelinePropertyRows = memo(function TimelinePropertyRows({
                 strokeWidth={1}
               />
               {propKeyframes.map((kf) => {
-                const x = (kf.percentage / 100) * clipWidthPx;
+                const x = Math.max(
+                  HALF,
+                  Math.min(clipWidthPx - HALF, (kf.percentage / 100) * clipWidthPx),
+                );
                 const y = SUB_TRACK_H / 2;
                 const key = `${elementId}:${kf.percentage}`;
                 const isKfSelected = selectedKeyframes.has(key);