Add an example for Qt 3D use from Rust

It's not really pleasant to use yet due to the amount of unsafe methods
and the into_raw calls which are needed to leave the life time
management to QObject's parent/child tree.

Clearly comes from QObject's parent/child tree fighting with Rust own
memory management and Qt 3D using heavily composition and not inheritance.
My goal is now to change the generator to simplify this code.

qt_generator/qt_generator/crate_templates/3d_extras/examples/lights.rs

@@ -0,0 +1,183 @@
+extern crate qt_core;
+extern crate qt_gui;
+extern crate qt_3d_core;
+extern crate qt_3d_input;
+extern crate qt_3d_logic;
+extern crate qt_3d_render;
+extern crate qt_3d_extras;
+
+use std::cell::*;
+
+use qt_core::connection::*;
+use qt_core::slots::*;
+
+use qt_gui::gui_application::GuiApplication;
+use qt_gui::color::*;
+use qt_gui::surface_format::*;
+use qt_gui::vector_3d::*;
+
+use qt_3d_core::cpp_utils::*;
+use qt_3d_core::entity::*;
+use qt_3d_core::node::*;
+use qt_3d_core::transform::*;
+
+use qt_3d_input::keyboard_device::*;
+use qt_3d_input::keyboard_handler::*;
+
+use qt_3d_render::directional_light::*;
+use qt_3d_render::point_light::*;
+use qt_3d_render::spot_light::*;
+
+use qt_3d_extras::qt_3d_window::*;
+use qt_3d_extras::metal_rough_material::*;
+use qt_3d_extras::orbit_camera_controller::*;
+use qt_3d_extras::plane_mesh::*;
+use qt_3d_extras::sphere_mesh::*;
+
+fn to_node_ptr(entity: &mut Entity) -> *mut Node {
+    static_cast_mut::<Node, Entity>(entity)
+}
+
+fn setup_scene(root: &mut Entity) -> Box<Fn() -> ()> {
+    let mut scene = unsafe { Entity::new_unsafe(to_node_ptr(root)) };
+
+    let mut sphere1 = unsafe { Entity::new_unsafe(to_node_ptr(scene.as_mut())) };
+    let mut sphere1_mesh = SphereMesh::new();
+    sphere1_mesh.set_radius(1.0);
+    sphere1_mesh.set_rings(60);
+    sphere1_mesh.set_slices(30);
+    unsafe { sphere1.add_component(static_cast_mut(sphere1_mesh.into_raw())) };
+    let mut sphere1_material = MetalRoughMaterial::new();
+    sphere1_material.set_base_color(&Color::from_rgb((255, 255, 255)));
+    sphere1_material.set_metalness(0.5);
+    sphere1_material.set_roughness(0.2);
+    unsafe { sphere1.add_component(static_cast_mut(sphere1_material.into_raw())) };
+    let mut sphere1_transform = Transform::new();
+    sphere1_transform.set_translation(&Vector3D::new((-2.0, 0.0, 0.0)));
+    unsafe { sphere1.add_component(static_cast_mut(sphere1_transform.into_raw())) };
+    sphere1.into_raw();
+
+    let mut sphere2 = unsafe { Entity::new_unsafe(to_node_ptr(scene.as_mut())) };
+    let mut sphere2_mesh = SphereMesh::new();
+    sphere2_mesh.set_radius(1.0);
+    sphere2_mesh.set_rings(60);
+    sphere2_mesh.set_slices(30);
+    unsafe { sphere2.add_component(static_cast_mut(sphere2_mesh.into_raw())) };
+    let mut sphere2_material = MetalRoughMaterial::new();
+    sphere2_material.set_base_color(&Color::from_rgb((255, 255, 255)));
+    sphere2_material.set_metalness(0.5);
+    sphere2_material.set_roughness(0.2);
+    unsafe { sphere2.add_component(static_cast_mut(sphere2_material.into_raw())) };
+    let mut sphere2_transform = Transform::new();
+    sphere2_transform.set_translation(&Vector3D::new((2.0, 0.0, 0.0)));
+    unsafe { sphere2.add_component(static_cast_mut(sphere2_transform.into_raw())) };
+    sphere2.into_raw();
+
+    let mut plane = unsafe { Entity::new_unsafe(to_node_ptr(scene.as_mut())) };
+    unsafe { plane.add_component(static_cast_mut(PlaneMesh::new().into_raw())) };
+    let mut plane_material = MetalRoughMaterial::new();
+    plane_material.set_base_color(&Color::from_rgb((255, 255, 255)));
+    plane_material.set_metalness(0.5);
+    plane_material.set_roughness(0.5);
+    unsafe { plane.add_component(static_cast_mut(plane_material.into_raw())) };
+    let mut plane_transform = Transform::new();
+    plane_transform.set_scale(100.0);
+    plane_transform.set_translation(&Vector3D::new((0.0, -2.0, 0.0)));
+    unsafe { plane.add_component(static_cast_mut(plane_transform.into_raw())) };
+    plane.into_raw();
+
+    let mut directional_light = DirectionalLight::new();
+    directional_light.set_enabled(true);
+    directional_light.set_color(&Color::from_rgb((255, 0, 0)));
+    directional_light.set_intensity(1.0);
+    directional_light.set_world_direction(&Vector3D::new((1.0, -1.0, 0.0)));
+    unsafe { scene.add_component(static_cast_mut(directional_light.as_mut_ptr())) };
+
+    let mut point_light_entity = unsafe { Entity::new_unsafe(to_node_ptr(scene.as_mut())) };
+    let mut point_light = PointLight::new();
+    point_light.set_enabled(false);
+    point_light.set_color(&Color::from_rgb((0, 255, 0)));
+    point_light.set_intensity(1.0);
+    point_light.set_linear_attenuation(0.01);
+    point_light.set_quadratic_attenuation(0.05);
+    unsafe { point_light_entity.add_component(static_cast_mut(point_light.as_mut_ptr())) };
+    let mut point_light_transform = Transform::new();
+    point_light_transform.set_translation(&Vector3D::new((0.0, 3.0, 1.0)));
+    unsafe { point_light_entity.add_component(static_cast_mut(point_light_transform.into_raw())) };
+    point_light_entity.into_raw();
+
+    let mut spot_light_entity = unsafe { Entity::new_unsafe(to_node_ptr(scene.as_mut())) };
+    let mut spot_light = SpotLight::new();
+    spot_light.set_enabled(false);
+    spot_light.set_color(&Color::from_rgb((0, 0, 255)));
+    spot_light.set_intensity(1.0);
+    spot_light.set_local_direction(&Vector3D::new((-1.0, -1.0, 0.0)));
+    spot_light.set_cut_off_angle(45.0);
+    spot_light.set_linear_attenuation(0.05);
+    spot_light.set_quadratic_attenuation(0.005);
+    unsafe { spot_light_entity.add_component(static_cast_mut(spot_light.as_mut_ptr())) };
+    let mut spot_light_transform = Transform::new();
+    spot_light_transform.set_translation(&Vector3D::new((6.0, 6.0, 0.0)));
+    unsafe { spot_light_entity.add_component(static_cast_mut(spot_light_transform.into_raw())) };
+    spot_light_entity.into_raw();
+
+    scene.into_raw();
+
+    let directional_light = directional_light.into_raw();
+    let point_light = point_light.into_raw();
+    let spot_light = spot_light.into_raw();
+
+    let active_light_cell = RefCell::new(0);
+    Box::new(move || {
+        let active_light = (*active_light_cell.borrow() + 1) % 3;
+        unsafe {
+            (*directional_light).set_enabled(active_light == 0);
+            (*point_light).set_enabled(active_light == 1);
+            (*spot_light).set_enabled(active_light == 2);
+        }
+        *active_light_cell.borrow_mut() = active_light;
+    })
+}
+
+fn main() {
+    let mut format = SurfaceFormat::new(());
+    format.set_version(3, 3);
+    format.set_profile(OpenGLContextProfile::Core);
+    format.set_depth_buffer_size(24);
+    format.set_samples(4);
+    format.set_stencil_buffer_size(8);
+    SurfaceFormat::set_default_format(&format);
+
+    GuiApplication::create_and_exit(|_| {
+        let mut window = Qt3DWindow::new();
+
+        let mut root = Entity::new();
+        let activate_next_light = setup_scene(&mut root);
+        let next_light_slot = SlotNoArgs::new(activate_next_light.as_ref());
+
+        let keyboard_device = unsafe { KeyboardDevice::new_unsafe(to_node_ptr(root.as_mut())) };
+        let mut handler = unsafe { Entity::new_unsafe(to_node_ptr(root.as_mut())) };
+        let mut keyboard_handler = KeyboardHandler::new();
+        unsafe { keyboard_handler.set_source_device(keyboard_device.into_raw()) };
+        keyboard_handler.set_focus(true);
+        keyboard_handler.signals().tab_pressed().connect(&next_light_slot);
+        keyboard_handler.signals().space_pressed().connect(&next_light_slot);
+        unsafe { handler.add_component(static_cast_mut(keyboard_handler.into_raw())) };
+        handler.into_raw();
+
+        let camera = window.camera();
+        unsafe { (*camera).set_position(&Vector3D::new((0.0, 0.0, 30.0))) };
+        unsafe { (*camera).set_view_center(&Vector3D::new((0.0, 0.0, 0.0))) };
+
+        let mut controller = unsafe { OrbitCameraController::new_unsafe(to_node_ptr(&mut root)) };
+        unsafe { controller.set_camera(camera) };
+        controller.set_linear_speed(50.0);
+        controller.set_look_speed(180.0);
+        controller.into_raw();
+
+        unsafe { window.set_root_entity(root.into_raw()) };
+
+        window.show();
+        GuiApplication::exec()
+    })
+}