refactor: continual refactor to support multiple render targets

thermion_dart/test/render_thread.dart

@@ -0,0 +1,33 @@
+import 'dart:async';
+import 'dart:ffi';
+import 'package:test/test.dart';
+
+import 'helpers.dart';
+
+void main() async {
+  final testHelper = TestHelper("render_thread");
+  group("render thread/capture", () {
+    test("request frame on render thread", () async {
+      var viewer = await testHelper.createViewer();
+      await viewer.setBackgroundColor(1.0, 0.0, 0.0, 1.0);
+
+      var texture = await testHelper.createTexture(500, 500);
+      var renderTarget = await viewer.createRenderTarget(
+          500, 500, texture.metalTextureAddress);
+      
+      final view = await viewer.getViewAt(0);
+      await view.setRenderTarget(renderTarget);
+
+      await viewer.render();
+
+      await Future.delayed(Duration(milliseconds: 1));
+
+      var data = texture.getTextureBytes()!;
+      var pixels = data.bytes.cast<Uint8>().asTypedList(data.length);
+
+      savePixelBufferToBmp(
+          pixels, 500, 500, "${testHelper.testDir}/request_frame.bmp");
+      await viewer.dispose();
+    });
+  });
+}