miniPaint/src/js/actions/reorder-layer.js

import app from '../app.js';
import config from '../config.js';
import { Base_action } from './base.js';

export class Reorder_layer_action extends Base_action {
	/**
	 * Reorder layer up or down in the layer stack
	 *
	 * @param {int} layer_id
	 * @param {int} direction
	 */
	constructor(layer_id, direction) {
        super('reorder_layer', 'Reorder Layer');
        this.layer_id = parseInt(layer_id);
        this.direction = direction;
        this.reference_layer = null;
        this.reference_target = null;
        this.old_layer_order = null;
        this.old_target_order = null;
	}

    async do() {
        super.do();
        this.reference_layer = app.Layers.get_layer(this.layer_id);
        if (!this.reference_layer) {
            throw new Error('Aborted - layer with specified id doesn\'t exist');
        }
		if (this.direction < 0) {
			this.reference_target = app.Layers.find_previous(this.layer_id);
		}
		else {
			this.reference_target = app.Layers.find_next(this.layer_id);
        }
        if (!this.reference_target) {
            throw new Error('Aborted - layer has nowhere to move');
        }
        this.old_layer_order = this.reference_layer.order;
        this.old_target_order = this.reference_target.order;
        this.reference_layer.order = this.old_target_order;
        this.reference_target.order = this.old_layer_order;

		app.Layers.render();
		app.GUI.GUI_layers.render_layers();
    }

    async undo() {
        super.undo();
        if (this.reference_layer) {
            this.reference_layer.order = this.old_layer_order;
            this.reference_layer = null;
        }
        if (this.reference_target) {
            this.reference_target.order = this.old_target_order;
            this.reference_target = null;
        }
        app.Layers.render();
		app.GUI.GUI_layers.render_layers();
    }

    free() {
        this.reference_layer = null;
        this.reference_target = null;
    }
}