LienzoEmptyScreen

package org.kie.workbench.common.stunner.client.lienzo.components.views;

import javax.enterprise.context.Dependent;

import com.ait.lienzo.client.core.shape.Group;
import com.ait.lienzo.client.core.shape.Layer;
import org.kie.workbench.common.stunner.client.lienzo.canvas.wires.WiresCanvas;
import org.kie.workbench.common.stunner.core.client.canvas.Canvas;
import org.kie.workbench.common.stunner.core.client.components.views.EmptyScreen;

@Dependent
public class LienzoEmptyScreen implements EmptyScreen {

    // This class contains the pure lienzo "empty screen" implementation object as a field
    // so it can be showed against some Canvas or hidden.

    private WiresCanvas canvas;
    private Group theLienzoEmptyScreenGroupInstance;

    @Override
    public void configure(Canvas canvas, String text) {
        // It allows to configure the lienzo "empty screen" to show different texts, on any Stunner's editor (Canvas)
        // This way, either BPMN, CM and DMN can reuse this component and just use different text literals
        this.canvas = (WiresCanvas) canvas;
        this.theLienzoEmptyScreenGroupInstance = /*create a new lienzo instance here*/;
        // etc
    }

    @Override
    public void show() {
        // It shows the "empty screen" into the right "Canvas"

        // The lienzo object for the "empty screen" will be attached to the "top" canvas layer, instead of the main one, for performance reasons
        getTargetLayer().add(theLienzoEmptyScreenGroupInstance);
        batch();
    }

    @Override
    public void hide() {
        theLienzoEmptyScreenGroupInstance.removeFromParent();
        batch();
    }

    @Override
    public void destroy() {
        theLienzoEmptyScreenGroupInstance.removeFromParent();
        theLienzoEmptyScreenGroupInstance = null;
        canvas = null;
        // etc
    }

    private void batch() {
        getTargetLayer().batch();
    }

    private Layer getTargetLayer() {
        return canvas.getView().getLayer().getTopLayer();
    }
}