feat: Silly debug draw demo

Author: Berstanio

src/test/java/com/badlogic/gdx/box2d/test/Box2dDrawTest.java

@@ -0,0 +1,117 @@
+package com.badlogic.gdx.box2d.test;
+
+import com.badlogic.gdx.box2d.Box2d;
+import com.badlogic.gdx.box2d.enums.b2BodyType;
+import com.badlogic.gdx.box2d.structs.b2BodyDef;
+import com.badlogic.gdx.box2d.structs.b2BodyId;
+import com.badlogic.gdx.box2d.structs.b2DebugDraw;
+import com.badlogic.gdx.box2d.structs.b2Polygon;
+import com.badlogic.gdx.box2d.structs.b2ShapeDef;
+import com.badlogic.gdx.box2d.structs.b2Vec2;
+import com.badlogic.gdx.box2d.structs.b2WorldDef;
+import com.badlogic.gdx.box2d.structs.b2WorldId;
+import com.badlogic.gdx.jnigen.runtime.closure.ClosureObject;
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.image.BufferStrategy;
+
+import static com.badlogic.gdx.box2d.Box2d.*;
+
+public class Box2dDrawTest {
+
+    private static final int e_columns = 100;
+    private static final int e_rows = 100;
+
+    public static void main (String[] args) {
+        Box2d.initialize();
+
+        b2WorldDef worldDef = b2DefaultWorldDef();
+        b2WorldId worldId = b2CreateWorld(worldDef.asPointer());
+
+        {
+            b2BodyDef bd = b2DefaultBodyDef();
+            bd.position().x(0.0f);
+            bd.position().y(-1.0f);
+            b2BodyId groundId = b2CreateBody(worldId, bd.asPointer());
+
+            b2Polygon box = b2MakeBox(1000.0f, 1.0f);
+            b2ShapeDef sd = b2DefaultShapeDef();
+            b2CreatePolygonShape(groundId, sd.asPointer(), box.asPointer());
+        }
+
+        b2Polygon box = b2MakeRoundedBox(0.45f, 0.45f, 0.05f);
+        b2ShapeDef sd = b2DefaultShapeDef();
+        sd.density(1.0f);
+        sd.friction(0.3f);
+
+        float offset = 0.2f;
+        float dx = 5.0f;
+        float xroot = -0.5f * dx * (e_columns - 1.0f);
+
+        for (int j = 0; j < e_columns; ++j) {
+            float x = xroot + j * dx;
+            for (int i = 0; i < e_rows; ++i) {
+                b2BodyDef bd = b2DefaultBodyDef();
+                bd.type(b2BodyType.b2_dynamicBody);
+                bd.position().x(x + offset * i);
+                bd.position().y(0.5f + 1.0f * i);
+
+                b2BodyId bodyId = b2CreateBody(worldId, bd.asPointer());
+                b2CreatePolygonShape(bodyId, sd.asPointer(), box.asPointer());
+            }
+        }
+
+
+        startLoop(worldId);
+    }
+
+    public static void startLoop(b2WorldId worldId) {
+        JFrame frame = new JFrame("Example");
+        frame.setSize(800, 600);
+        frame.setVisible(true);
+        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        frame.setResizable(false);
+
+        Canvas canvas = new Canvas();
+        frame.add(canvas);
+        canvas.createBufferStrategy(2);
+
+        b2DebugDraw draw = b2DefaultDebugDraw();
+        draw.drawAABBs(true);
+
+        draw.DrawPolygon(ClosureObject.fromClosure((vertices, vertexCount, color, context) -> {
+            BufferStrategy bs = canvas.getBufferStrategy();
+            Graphics g = bs.getDrawGraphics();
+
+
+            Polygon polygon = new Polygon();
+            for (int i = 0; i < vertexCount; i++) {
+                b2Vec2 vec2 = vertices.get(i);
+                polygon.addPoint((int)vec2.x() * 10, (int)vec2.y() * 10);
+            }
+
+            g.setColor(new Color(color.getIndex()));
+            g.drawPolygon(polygon);
+
+        }));
+
+        Timer timer = new Timer(1000 / 60, e -> {
+            float timeStep = 1.0f / 60.0f;
+            int subStepCount = 4;
+            b2World_Step(worldId, timeStep, subStepCount);
+
+            BufferStrategy bs = canvas.getBufferStrategy();
+            Graphics g = bs.getDrawGraphics();
+            g.setColor(Color.BLACK);
+            g.fillRect(0, 0, canvas.getWidth(), canvas.getHeight());
+
+            b2World_Draw(worldId, draw.asPointer());
+
+            g.dispose();
+            bs.show();
+        });
+
+        timer.start();
+    }
+}