Add a convenience method for creating a scene proxy with an empty scene.

This makes animation rendering loops a bit easier for users.

Cargo.lock

@@ -180,7 +180,6 @@ dependencies = [
  "pathfinder_gl 0.1.0",
  "pathfinder_gpu 0.1.0",
  "pathfinder_renderer 0.1.0",
- "pretty_env_logger 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sdl2 0.32.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "sdl2-sys 0.32.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

demo/common/src/lib.rs

@@ -143,7 +143,7 @@ impl<W> DemoApp<W> where W: Window {
                                                                   viewport.size());
         let camera = Camera::new(options.mode, scene_metadata.view_box, viewport.size());
 
-        let scene_proxy = SceneProxy::new(built_svg.scene, executor);
+        let scene_proxy = SceneProxy::from_scene(built_svg.scene, executor);
 
         let ground_program = GroundProgram::new(&renderer.device, resources);
         let ground_vertex_array = GroundVertexArray::new(&renderer.device,

examples/canvas_minimal/src/main.rs

@@ -74,7 +74,7 @@ fn main() {
     canvas.stroke_path(path);
 
     // Render the canvas to screen.
-    let scene = SceneProxy::new(canvas.into_scene(), RayonExecutor);
+    let scene = SceneProxy::from_scene(canvas.into_scene(), RayonExecutor);
     scene.build_and_render(&mut renderer, RenderOptions::default());
     window.gl_swap_window();
 

examples/canvas_moire/Cargo.toml

@@ -6,7 +6,6 @@ edition = "2018"
 
 [dependencies]
 gl = "0.6"
-pretty_env_logger = "0.3"
 sdl2 = "0.32"
 sdl2-sys = "0.32"
 

examples/canvas_moire/src/main.rs

@@ -37,8 +37,6 @@ const CIRCLE_THICKNESS: f32 = 16.0;
 const COLOR_CYCLE_SPEED: f32 = 0.0025;
 
 fn main() {
-    pretty_env_logger::init();
-
     // Set up SDL2.
     let sdl_context = sdl2::init().unwrap();
     let video = sdl_context.video().unwrap();
@@ -87,7 +85,7 @@ fn main() {
 
 struct MoireRenderer {
     renderer: Renderer<GLDevice>,
-    scene: Option<SceneProxy>,
+    scene: SceneProxy,
     frame: i32,
     window_size: Point2DI32,
     drawable_size: Point2DI32,
@@ -100,7 +98,7 @@ impl MoireRenderer {
            -> MoireRenderer {
         MoireRenderer {
             renderer,
-            scene: None,
+            scene: SceneProxy::new(RayonExecutor),
             frame: 0,
             window_size,
             drawable_size,
@@ -138,16 +136,9 @@ impl MoireRenderer {
         self.draw_circles(&mut canvas, outer_center);
         self.draw_circles(&mut canvas, inner_center);
 
-        // Build scene if necessary.
-        // TODO(pcwalton): Allow the user to build an empty scene proxy so they don't have to do this.
-        match self.scene {
-            None => self.scene = Some(SceneProxy::new(canvas.into_scene(), RayonExecutor)),
-            Some(ref mut scene) => scene.replace_scene(canvas.into_scene()),
-        }
-
-        // Render the scene.
-        self.scene.as_mut().unwrap().build_and_render(&mut self.renderer,   
-                                                      RenderOptions::default());
+        // Build and render scene.
+        self.scene.replace_scene(canvas.into_scene());
+        self.scene.build_and_render(&mut self.renderer, RenderOptions::default());
 
         self.frame += 1;
     }

examples/canvas_text/src/main.rs

@@ -62,7 +62,7 @@ fn main() {
     canvas.stroke_text("Goodbye Pathfinder!", Point2DF32::new(32.0, 96.0));
 
     // Render the canvas to screen.
-    let scene = SceneProxy::new(canvas.into_scene(), RayonExecutor);
+    let scene = SceneProxy::from_scene(canvas.into_scene(), RayonExecutor);
     scene.build_and_render(&mut renderer, RenderOptions::default());
     window.gl_swap_window();
 

geometry/src/outline.rs

@@ -369,14 +369,12 @@ impl Contour {
             let rotation = Transform2DF32::from_rotation(angle);
             segment = segment.transform(&scale.post_mul(&rotation).post_mul(&translation));
 
-            /*
-            println!("angle={} start_angle={} end_angle={} sweep_angle={} segment={:?}",
+            debug!("angle={} start_angle={} end_angle={} sweep_angle={} segment={:?}",
                    angle,
                    start_angle,
                    end_angle,
                    sweep_angle,
                    segment);
-            */
 
             if first_segment {
                 self.push_full_segment(&segment, true);

renderer/src/concurrent/scene_proxy.rs

@@ -36,7 +36,12 @@ pub struct SceneProxy {
 }
 
 impl SceneProxy {
-    pub fn new<E>(scene: Scene, executor: E) -> SceneProxy where E: Executor + Send + 'static {
+    pub fn new<E>(executor: E) -> SceneProxy where E: Executor + Send + 'static {
+        SceneProxy::from_scene(Scene::new(), executor)
+    }
+
+    pub fn from_scene<E>(scene: Scene, executor: E) -> SceneProxy
+                         where E: Executor + Send + 'static {
         let (main_to_worker_sender, main_to_worker_receiver) = mpsc::channel();
         thread::spawn(move || scene_thread(scene, executor, main_to_worker_receiver));
         SceneProxy { sender: main_to_worker_sender }