change android icon, move code so .cpp and implement stroke preview using Stroke class for accurate preview.

android/src/main/cpp/main.cpp

@@ -167,6 +167,10 @@ static void engine_draw_frame(struct engine* engine) {
     if (engine->display == NULL)
         return;
 
+    glClearColor(.1f, .1f, .1f, 1.f);
+    glViewport(0, 0, (GLsizei)engine->width, (GLsizei)engine->height);
+    glClear(GL_COLOR_BUFFER_BIT);
+
     App::I.update(0);
 
     eglSwapBuffers(engine->display, engine->surface);

android/src/main/res/values/strings.xml

@@ -1,4 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <string name="app_name">LayoutEngine</string>
+    <string name="app_name">PanoPainter</string>
 </resources>