After Effects JSX Script - Offset markers

offsetMarkers.jsx

/*
After Effects JSX Script
Offset markers V2
Author: G.Breant + Claude
*/
(function offsetMarkers() {
    var comp = app.project.activeItem;
    if (!comp || !(comp instanceof CompItem)) {
        alert("Open a composition first.");
        return;
    }

    // ── UI ────────────────────────────────────────────────────────────────
    var dlg = new Window("dialog", "Offset Markers");
    dlg.orientation = "column";
    dlg.alignChildren = ["fill", "top"];
    dlg.margins = 18;
    dlg.spacing = 12;

    var framesGrp = dlg.add("group");
    framesGrp.add("statictext", undefined, "Offset (frames):");
    var framesInput = framesGrp.add("edittext", undefined, "10");
    framesInput.preferredSize.width = 60;

    var dirGrp = dlg.add("group");
    dirGrp.add("statictext", undefined, "Active area:");
    var dirMenu = dirGrp.add("dropdownlist", undefined,
        ["All", "Before playhead only", "After playhead only", "Work area"]);
    dirMenu.selection = 2;
    dirMenu.preferredSize.width = 180;

    var targetGrp = dlg.add("group");
    targetGrp.add("statictext", undefined, "Target:");
    var targetMenu = targetGrp.add("dropdownlist", undefined,
        ["Comp + all layers", "Comp markers only", "Layer markers only"]);
    targetMenu.selection = 1;
    targetMenu.preferredSize.width = 180;

    var btnGrp = dlg.add("group");
    btnGrp.alignment = "right";
    var cancelBtn = btnGrp.add("button", undefined, "Cancel", { name: "cancel" });
    var okBtn     = btnGrp.add("button", undefined, "OK",     { name: "ok" });

    cancelBtn.onClick = function () { dlg.close(); };

    okBtn.onClick = function () {
        var frames = parseInt(framesInput.text, 10);
        if (isNaN(frames) || frames === 0) {
            alert("Enter a non-zero integer number of frames.");
            return;
        }

        var dir      = dirMenu.selection.index;    // 0 both | 1 before | 2 after | 3 work area
        var target   = targetMenu.selection.index; // 0 both | 1 comp   | 2 layers
        var fps      = comp.frameRate;
        var playhead = comp.time;                  // seconds
        var offsetSec = frames / fps;              // convert frames → seconds

        // ── work area bounds (only computed when needed) ───────────────
        var workAreaStart = comp.workAreaStart;
        var workAreaEnd   = comp.workAreaStart + comp.workAreaDuration;

        // ── helper: should this marker time be shifted? ────────────────
        function shouldOffset(markerTime) {
            if (dir === 0) return true;
            if (dir === 1) return markerTime <  playhead;
            if (dir === 2) return markerTime >= playhead;
            if (dir === 3) return markerTime >= workAreaStart && markerTime < workAreaEnd;
        }

        // ── helper: shift a MarkerValueCollection ──────────────────────
        function shiftMarkers(markerCollection) {
            var indices = [];
            for (var i = 1; i <= markerCollection.numKeys; i++) {
                indices.push(i);
            }
            // Iterate in reverse when moving forward to avoid key collisions
            if (offsetSec > 0) indices.reverse();

            for (var j = 0; j < indices.length; j++) {
                var idx = indices[j];
                var t   = markerCollection.keyTime(idx);
                if (shouldOffset(t)) {
                    var mv = markerCollection.keyValue(idx);
                    markerCollection.removeKey(idx);
                    markerCollection.setValueAtTime(t + offsetSec, mv);
                }
            }
        }

        app.beginUndoGroup("Offset Markers");

        // ── Comp markers ───────────────────────────────────────────────
        if (target === 0 || target === 1) {
            shiftMarkers(comp.markerProperty);
        }

        // ── Layer markers ──────────────────────────────────────────────
        if (target === 0 || target === 2) {
            for (var li = 1; li <= comp.numLayers; li++) {
                var layer = comp.layer(li);
                if (layer.marker && layer.marker.numKeys > 0) {
                    shiftMarkers(layer.marker);
                }
            }
        }

        app.endUndoGroup();
        dlg.close();
        alert("Done. Markers offset by " + frames + " frame(s).");
    };

    dlg.show();
})();