Add events for GuiComponent rendering

core/src/main/java/de/gurkenlabs/litiengine/gui/ComponentRenderEvent.java

@@ -0,0 +1,41 @@
+package de.gurkenlabs.litiengine.gui;
+
+import java.awt.Graphics2D;
+import java.util.EventObject;
+
+public class ComponentRenderEvent extends EventObject {
+
+  private final transient Graphics2D graphics;
+  private final transient GuiComponent component;
+
+  /**
+   * Constructs a prototypical Event.
+   *
+   * @param source the object on which the Event initially occurred
+   * @throws IllegalArgumentException if source is null
+   */
+  public ComponentRenderEvent(final Graphics2D graphics, final GuiComponent source) {
+    super(source);
+
+    this.graphics = graphics;
+    this.component = source;
+  }
+
+  /**
+   * Get the component involved with the rendering process.
+   *
+   * @return The component involved with the rendering process.
+   */
+  public GuiComponent getComponent() {
+    return this.component;
+  }
+
+  /**
+   * Gets the graphics object on which the entity is rendered.
+   *
+   * @return The graphics object on which the entity is rendered.
+   */
+  public Graphics2D getGraphics() {
+    return this.graphics;
+  }
+}

core/src/main/java/de/gurkenlabs/litiengine/gui/ComponentRenderListener.java

@@ -0,0 +1,32 @@
+package de.gurkenlabs.litiengine.gui;
+
+import de.gurkenlabs.litiengine.entities.EntityRenderEvent;
+import java.awt.Graphics2D;
+
+/**
+ * This listener interface is used for receiving events during a component's rendering process.
+ *
+ * @see GuiComponent#render(Graphics2D)
+ */
+public interface ComponentRenderListener extends ComponentRenderedListener {
+
+  /**
+   * This method gets called after all rendering checks have successfully passed and right before
+   * the component is about to be rendered.
+   *
+   * @param event The event that contains the render data.
+   */
+  default void rendering(ComponentRenderEvent event) {
+  }
+
+  /**
+   * This method gets called before an {@code GuiComponent} is about to be rendered. Returning false
+   * prevents the rendering of the specified component.
+   *
+   * @param component The component to be rendered.
+   * @return True if the component should be rendered; otherwise false.
+   */
+  default boolean canRender(GuiComponent component) {
+    return true;
+  }
+}

core/src/main/java/de/gurkenlabs/litiengine/gui/ComponentRenderedListener.java

@@ -0,0 +1,20 @@
+package de.gurkenlabs.litiengine.gui;
+
+import java.awt.Graphics2D;
+import java.util.EventListener;
+
+/**
+ * This listener interface is used for receiving events after an component was rendered.
+ *
+ * @see GuiComponent#render(Graphics2D)
+ */
+@FunctionalInterface
+public interface ComponentRenderedListener extends EventListener {
+
+  /**
+   * This method gets called after an {@link GuiComponent} was rendered.
+   *
+   * @param event The event that contains the render data.
+   */
+  void rendered(ComponentRenderEvent event);
+}

core/src/main/java/de/gurkenlabs/litiengine/gui/GuiComponent.java

@@ -28,7 +28,9 @@
 import java.awt.geom.Rectangle2D;
 import java.awt.geom.RectangularShape;
 import java.awt.geom.RoundRectangle2D;
+import java.util.Collection;
 import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Consumer;
 
@@ -59,6 +61,9 @@ public abstract class GuiComponent
   private final List<Consumer<ComponentMouseEvent>> hoverConsumer;
   private final List<Consumer<String>> textChangedConsumer;
 
+  private final Collection<ComponentRenderListener> renderListeners = ConcurrentHashMap.newKeySet();
+  private final Collection<ComponentRenderedListener> renderedListeners = ConcurrentHashMap.newKeySet();
+
   private final int componentId;
   private final Appearance appearance;
   private final Appearance hoveredAppearance;
@@ -110,9 +115,9 @@ protected GuiComponent(final double x, final double y) {
   /**
    * Instantiates a new gui component at the point (x,y) with the dimension (width,height).
    *
-   * @param x the x
-   * @param y the y
-   * @param width the width
+   * @param x      the x
+   * @param y      the y
+   * @param width  the width
    * @param height the height
    */
   protected GuiComponent(final double x, final double y, final double width, final double height) {
@@ -705,6 +710,22 @@ public void onTextChanged(final Consumer<String> cons) {
     this.textChangedConsumer.add(cons);
   }
 
+  public void addRenderListener(final ComponentRenderListener listener) {
+    this.renderListeners.add(listener);
+  }
+
+  public void removeListener(final ComponentRenderListener listener) {
+    this.renderListeners.remove(listener);
+  }
+
+  public void addRenderedListener(final ComponentRenderedListener listener) {
+    this.renderedListeners.add(listener);
+  }
+
+  public void removeListener(final ComponentRenderedListener listener) {
+    this.renderedListeners.remove(listener);
+  }
+
   /**
    * Prepare the GuiComponent and all its child Components (Makes the GuiComponent visible and adds
    * mouse listeners.). This is, for example, done right before switching to a new screen.
@@ -730,6 +751,17 @@ public void render(final Graphics2D g) {
       return;
     }
 
+    for (ComponentRenderListener listener : this.renderListeners) {
+      if (!listener.canRender(this)) {
+        return;
+      }
+    }
+
+    final ComponentRenderEvent event = new ComponentRenderEvent(g, this);
+    for (ComponentRenderListener listener : this.renderListeners) {
+      listener.rendering(event);
+    }
+
     Shape clip = g.getClip();
     g.clip(this.getShape());
 
@@ -760,6 +792,14 @@ && getCurrentAppearance().getBorderStyle() != null) {
       component.render(g);
     }
 
+    for (ComponentRenderListener listener : this.renderListeners) {
+      listener.rendered(event);
+    }
+
+    for (ComponentRenderedListener listener : this.renderedListeners) {
+      listener.rendered(event);
+    }
+
     if (Game.config().debug().renderGuiComponentBoundingBoxes()) {
       g.setColor(Color.RED);
       ShapeRenderer.renderOutline(g, this.getBoundingBox());
@@ -770,33 +810,33 @@ && getCurrentAppearance().getBorderStyle() != null) {
   public float[] getTweenValues(TweenType tweenType) {
     switch (tweenType) {
       case POSITION_X:
-        return new float[] {(float) this.getX()};
+        return new float[]{(float) this.getX()};
       case POSITION_Y:
-        return new float[] {(float) this.getY()};
+        return new float[]{(float) this.getY()};
       case POSITION_XY:
-        return new float[] {(float) this.getX(), (float) this.getY()};
+        return new float[]{(float) this.getX(), (float) this.getY()};
       case SIZE_WIDTH:
-        return new float[] {(float) this.getWidth()};
+        return new float[]{(float) this.getWidth()};
       case SIZE_HEIGHT:
-        return new float[] {(float) this.getHeight()};
+        return new float[]{(float) this.getHeight()};
       case SIZE_BOTH:
-        return new float[] {(float) this.getWidth(), (float) this.getHeight()};
+        return new float[]{(float) this.getWidth(), (float) this.getHeight()};
       case ANGLE:
-        return new float[] {(float) this.getTextAngle()};
+        return new float[]{(float) this.getTextAngle()};
       case FONTSIZE:
-        return new float[] {this.getFont().getSize2D()};
+        return new float[]{this.getFont().getSize2D()};
       case OPACITY:
         Color bg1 = this.getCurrentAppearance().getBackgroundColor1();
         Color bg2 = this.getCurrentAppearance().getBackgroundColor2();
         Color fore = this.getCurrentAppearance().getForeColor();
         Color shadow = this.getTextShadowColor();
         Color border = this.getCurrentAppearance().getBorderColor();
-        return new float[] {
-          (float) (bg1 == null ? 0 : bg1.getAlpha()),
-          (float) (bg2 == null ? 0 : bg2.getAlpha()),
-          (float) (fore == null ? 0 : fore.getAlpha()),
-          (float) (shadow == null ? 0 : shadow.getAlpha()),
-          (float) (border == null ? 0 : border.getAlpha())
+        return new float[]{
+            (float) (bg1 == null ? 0 : bg1.getAlpha()),
+            (float) (bg2 == null ? 0 : bg2.getAlpha()),
+            (float) (fore == null ? 0 : fore.getAlpha()),
+            (float) (shadow == null ? 0 : shadow.getAlpha()),
+            (float) (border == null ? 0 : border.getAlpha())
         };
       default:
         return Tweenable.super.getTweenValues(tweenType);
@@ -879,7 +919,7 @@ public RectangularShape getShape() {
   /**
    * Sets the width and height of this GuiComponent.
    *
-   * @param width the width
+   * @param width  the width
    * @param height the height
    */
   public void setDimension(final double width, final double height) {
@@ -1019,7 +1059,7 @@ public void setText(final String text) {
    * Sets the {@link RenderingHints#KEY_TEXT_ANTIALIASING} settings for the rendered text.
    *
    * @param antialiasing Either {@link RenderingHints#VALUE_TEXT_ANTIALIAS_ON} or {@link
-   *     RenderingHints#VALUE_TEXT_ANTIALIAS_OFF}
+   *                     RenderingHints#VALUE_TEXT_ANTIALIAS_OFF}
    */
   public void setTextAntialiasing(boolean antialiasing) {
     this.textAntialiasing = antialiasing;
@@ -1149,7 +1189,9 @@ public void suspend() {
     }
   }
 
-  /** Toggle this GuiComponent's selection. */
+  /**
+   * Toggle this GuiComponent's selection.
+   */
   public void toggleSelection() {
     this.setSelected(!this.isSelected);
   }
@@ -1254,7 +1296,9 @@ protected List<Consumer<ComponentMouseWheelEvent>> getMouseWheelConsumer() {
     return this.mouseWheelConsumer;
   }
 
-  /** Initialize child components. */
+  /**
+   * Initialize child components.
+   */
   protected void initializeComponents() {
     // nothing to do in the base class
   }