Add static lighting game object (#202)

* (#68) add light2d

src/main/java/tech/fastj/graphics/game/Light2D.java

@@ -0,0 +1,58 @@
+package tech.fastj.graphics.game;
+
+import tech.fastj.math.Pointf;
+
+import tech.fastj.graphics.Drawable;
+import tech.fastj.graphics.util.DrawUtil;
+
+import tech.fastj.systems.control.Scene;
+import tech.fastj.systems.control.SimpleManager;
+
+import java.awt.AlphaComposite;
+import java.awt.Composite;
+import java.awt.Graphics2D;
+import java.awt.Paint;
+import java.awt.RadialGradientPaint;
+
+public class Light2D extends GameObject {
+
+    private final AlphaComposite alphaComposite;
+    private final RadialGradientPaint gradient;
+
+    protected Light2D(Pointf location, Pointf size, RadialGradientPaint gradient, AlphaComposite alphaComposite) {
+        this.alphaComposite = alphaComposite;
+        this.gradient = gradient;
+        setCollisionPath(DrawUtil.createPath(DrawUtil.createBox(location, size)));
+    }
+
+    public static Light2DBuilder create(Pointf location, Pointf size) {
+        return new Light2DBuilder(location, size, Drawable.DefaultShouldRender);
+    }
+
+    public static Light2DBuilder create(Pointf location, Pointf size, boolean shouldRender) {
+        return new Light2DBuilder(location, size, shouldRender);
+    }
+
+    @Override
+    public void destroy(Scene origin) {
+        super.destroyTheRest(origin);
+    }
+
+    @Override
+    public void destroy(SimpleManager origin) {
+        super.destroyTheRest(origin);
+    }
+
+    @Override
+    public void render(Graphics2D g) {
+        Composite oldComposite = g.getComposite();
+        Paint oldPaint = g.getPaint();
+
+        g.setComposite(alphaComposite);
+        g.setPaint(gradient);
+        g.fill(getCollisionPath());
+
+        g.setComposite(oldComposite);
+        g.setPaint(oldPaint);
+    }
+}

src/main/java/tech/fastj/graphics/game/Light2DBuilder.java

@@ -0,0 +1,63 @@
+package tech.fastj.graphics.game;
+
+import tech.fastj.math.Pointf;
+
+import tech.fastj.graphics.gradients.Gradients;
+
+import java.awt.AlphaComposite;
+import java.awt.Color;
+import java.awt.RadialGradientPaint;
+import java.util.Objects;
+
+/** A builder class for creating {@link Light2D} objects. */
+public class Light2DBuilder {
+    private final boolean shouldRender;
+    private final Pointf location;
+    private final Pointf size;
+
+    private AlphaComposite alphaComposite = AlphaComposite.SrcOver;
+    private RadialGradientPaint gradientPaint;
+
+    Light2DBuilder(Pointf location, Pointf size, boolean shouldRender) {
+        this.location = location;
+        this.size = size;
+        this.shouldRender = shouldRender;
+    }
+
+    public Light2DBuilder withGradient(RadialGradientPaint gradientPaint) {
+        this.gradientPaint = Objects.requireNonNull(gradientPaint, "The radial gradient paint should not be null.");
+        return this;
+    }
+
+    public Light2DBuilder withGradient(Color centerColor, Color outerColor) {
+        Objects.requireNonNull(centerColor, "The center color should not be null.");
+        Objects.requireNonNull(outerColor, "The outer color should not be null.");
+        this.gradientPaint = Gradients.radialGradient(Pointf.add(location, size.copy().divide(2f)), evaluateRadius())
+                .withColors(centerColor, outerColor)
+                .build();
+        return this;
+    }
+
+    public Light2DBuilder withAlphaComposite(AlphaComposite alphaComposite) {
+        this.alphaComposite = Objects.requireNonNull(alphaComposite, "The alpha composite should not be null.");
+        return this;
+    }
+
+    /**
+     * Creates a new {@link Light2D} object, using the data provided by earlier method calls.
+     *
+     * @return The resulting {@code Light2D}.
+     */
+    public Light2D build() {
+        return (Light2D) new Light2D(location, size, gradientPaint, alphaComposite)
+                .setShouldRender(shouldRender);
+    }
+
+    private float evaluateRadius() {
+        Pointf horizontalSide = Pointf.subtract(Pointf.add(location, size.x, 0f), location);
+        Pointf verticalSide = Pointf.subtract(Pointf.add(location, 0f, size.y), location);
+
+        Pointf smallestSide = horizontalSide.squareMagnitude() < verticalSide.squareMagnitude() ? horizontalSide : verticalSide;
+        return smallestSide.magnitude() / 2.0f;
+    }
+}