Added ability to swap renderers

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_renderer/lib/base_renderer.dart

@@ -0,0 +1,72 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/scheduler.dart';
+import 'package:wolf_3d_engine/wolf_3d_engine.dart';
+import 'package:wolf_3d_input/wolf_3d_input.dart';
+
+// 1. The widget now only requires the engine!
+abstract class BaseWolfRenderer extends StatefulWidget {
+  final WolfEngine engine;
+  final Wolf3dInput inputManager;
+
+  const BaseWolfRenderer({
+    required this.engine,
+    required this.inputManager,
+    super.key,
+  });
+}
+
+abstract class BaseWolfRendererState<T extends BaseWolfRenderer>
+    extends State<T>
+    with SingleTickerProviderStateMixin {
+  late final Ticker gameLoop;
+  final FocusNode focusNode = FocusNode();
+
+  Duration _lastTick = Duration.zero;
+
+  @override
+  void initState() {
+    super.initState();
+    // DO NOT initialize the engine here. Just start the loop!
+    gameLoop = createTicker(_tick)..start();
+    focusNode.requestFocus();
+  }
+
+  void _tick(Duration elapsed) {
+    if (!widget.engine.isInitialized) return;
+
+    Duration delta = elapsed - _lastTick;
+    _lastTick = elapsed;
+
+    widget.inputManager.update();
+    // Tick the shared engine
+    widget.engine.tick(delta, widget.inputManager.currentInput);
+
+    performRender();
+  }
+
+  @override
+  void dispose() {
+    gameLoop.dispose();
+    focusNode.dispose();
+    super.dispose();
+  }
+
+  void performRender();
+  Widget buildViewport(BuildContext context);
+  Color get scaffoldColor;
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      backgroundColor: scaffoldColor,
+      body: KeyboardListener(
+        focusNode: focusNode,
+        autofocus: true,
+        onKeyEvent: (_) {},
+        child: Center(
+          child: buildViewport(context),
+        ),
+      ),
+    );
+  }
+}