Create visible parameter in GUI

api/src/main/java/com/bartlomiejpluta/base/api/game/gui/base/GUI.java

@@ -26,6 +26,14 @@ public interface GUI extends Renderable, Disposable, KeyEventHandler {
 
    Window inflateWindow(String widgetUid);
 
+   boolean isVisible();
+
+   void setVisible(boolean visible);
+
+   void show();
+
+   void hide();
+
    Widget getRoot();
 
    void setRoot(Widget root);

engine/src/main/java/com/bartlomiejpluta/base/engine/gui/render/NanoVGGUI.java

@@ -47,6 +47,8 @@ public class NanoVGGUI implements GUI {
    private final Set<String> loadedFonts = new HashSet<>();
    private final Map<String, NanoVGImage> loadedImages = new HashMap<>();
 
+   private boolean visible = true;
+
    public void init(Screen screen) {
       nvg = nvgCreate(NVG_ANTIALIAS | NVG_STENCIL_STROKES);
 
@@ -59,6 +61,10 @@ public class NanoVGGUI implements GUI {
 
    @Override
    public void render(Screen screen, Camera camera, ShaderManager shaderManager) {
+      if (!visible) {
+         return;
+      }
+
       nvgBeginFrame(nvg, screen.getWidth(), screen.getHeight(), 1);
 
       screenWidget.draw(screen, this);
@@ -80,6 +86,26 @@ public class NanoVGGUI implements GUI {
       return inflater.inflateWindow(is, context, this);
    }
 
+   @Override
+   public boolean isVisible() {
+      return visible;
+   }
+
+   @Override
+   public void setVisible(boolean visible) {
+      this.visible = visible;
+   }
+
+   @Override
+   public void show() {
+      this.visible = true;
+   }
+
+   @Override
+   public void hide() {
+      this.visible = false;
+   }
+
    @Override
    public Widget getRoot() {
       return screenWidget.getRoot();