// Select Next Layer (invisible or not).jsx
// https://gist.github.com/joonaspaakko/048c9b58ccbb6e6f44c894bf4ce30b68
nextLayer('down');
// direction (↑): "up" or "above"
// direction (↓): "down" or "below"
function nextLayer( direction ) {
var doc = app.activeDocument;
// Doc duplication is necessary because while the History panel can record visibility change, but for some reason it doesn't do that when the visibility command comes from a script... (AFAIK)
var tempDoc = doc.duplicate();
var layer1 = tempDoc.activeLayer;
// Turn background layer into a normal layer
var lastLayer = tempDoc.layers[ tempDoc.layers.length-1 ];
function cTID(s) { return app.charIDToTypeID(s); };
function sTID(s) { return app.stringIDToTypeID(s); };
var layer1ID = activeLayerID();
tempDoc.activeLayer = lastLayer;
var bgLayerExists = lastLayer.isBackgroundLayer;
if ( bgLayerExists ) { lastLayer.isBackgroundLayer = false; }
try { selectLayerByID( layer1ID ); } catch(e) {}
// Select all layers
var desc23 = new ActionDescriptor();
var ref5 = new ActionReference();
ref5.putEnumerated( cTID('Lyr '), cTID('Ordn'), cTID('Trgt') );
desc23.putReference( cTID('null'), ref5 );
executeAction( sTID('selectAllLayers'), desc23, DialogModes.NO );
// Make active layers visible
var desc209 = new ActionDescriptor();
var list93 = new ActionList();
var ref129 = new ActionReference();
ref129.putEnumerated( cTID('Lyr '), cTID('Ordn'), cTID('Trgt') );
list93.putReference( ref129 );
desc209.putList( cTID('null'), list93 );
executeAction( cTID('Shw '), desc209, DialogModes.NO );
// Reselect the starting layer
if ( bgLayerExists ) { lastLayer.isBackgroundLayer = true; }
selectLayerByID( layer1ID );
// Select next layer
try { snl( direction ); } catch(e) {}
// Store the layer
var nextLayer = activeLayerID();
tempDoc.close( SaveOptions.DONOTSAVECHANGES );
// Try to select the next layer using its ID
try {
selectLayerByID( nextLayer );
}
// If it fails, well assume it did so because it was a background layer... and use another method for selecting that.
catch(e) {
var desc299 = new ActionDescriptor();
var ref187 = new ActionReference();
ref187.putName( cTID('Lyr '), "Background" );
desc299.putReference( cTID('null'), ref187 );
desc299.putBoolean( cTID('MkVs'), false );
var list138 = new ActionList();
list138.putInteger( 1 );
desc299.putList( cTID('LyrI'), list138 );
executeAction( cTID('slct'), desc299, DialogModes.NO );
}
function snl( direction ) {
var select;
if ( direction == 'up' || direction == 'above' ) {
select = cTID('Frwr');
}
else if ( direction == 'down' || direction == 'below' ) {
select = cTID('Bckw');
}
var desc67 = new ActionDescriptor();
var ref41 = new ActionReference();
ref41.putEnumerated( cTID('Lyr '), cTID('Ordn'), select );
desc67.putReference( cTID('null'), ref41 );
desc67.putBoolean( cTID('MkVs'), false );
var list17 = new ActionList();
list17.putInteger( 5 );
desc67.putList( cTID('LyrI'), list17 );
executeAction( cTID('slct'), desc67, DialogModes.NO );
}
function activeLayerID() {
var ref = new ActionReference();
ref.putProperty( charIDToTypeID("Prpr") , charIDToTypeID( "LyrI" ));
ref.putEnumerated( charIDToTypeID("Lyr "), charIDToTypeID("Ordn"), charIDToTypeID("Trgt") );
return executeActionGet(ref).getInteger( stringIDToTypeID( "layerID" ) );
}
function selectLayerByID(id, add){
add = (add == undefined) ? add = false : add;
var ref = new ActionReference();
ref.putIdentifier(cTID('Lyr '), id);
var desc = new ActionDescriptor();
desc.putReference(cTID('null'), ref);
if(add){
desc.putEnumerated(sTID('selectionModifier'), sTID('selectionModifierType'), sTID('addToSelection'));
}
desc.putBoolean(cTID('MkVs'), false);
executeAction(cTID('slct'), desc, DialogModes.NO);
}
}