Auto merge of #404 - leroycep:minimal-example-rerendering, r=pcwalton

Make `canvas_minimal` example rerender on refresh

I'm not sure if this actually works, because the `canvas_minimal` example doesn't run on my computer.

Author: bors-servo

examples/canvas_minimal/src/main.rs

@@ -81,47 +81,55 @@ fn main() {
     let resource_loader = EmbeddedResourceLoader::new();
     let mut renderer = Renderer::new(pathfinder_device, &resource_loader, mode, options);
 
-    // Make a canvas. We're going to draw a house.
     let font_context = CanvasFontContext::from_system_source();
-    let mut canvas = Canvas::new(framebuffer_size.to_f32()).get_context_2d(font_context);
-
-    // Set line width.
-    canvas.set_line_width(10.0);
-
-    // Draw walls.
-    canvas.stroke_rect(RectF::new(vec2f(75.0, 140.0), vec2f(150.0, 110.0)));
-
-    // Draw door.
-    canvas.fill_rect(RectF::new(vec2f(130.0, 190.0), vec2f(40.0, 60.0)));
-
-    // Draw roof.
-    let mut path = Path2D::new();
-    path.move_to(vec2f(50.0, 140.0));
-    path.line_to(vec2f(150.0, 60.0));
-    path.line_to(vec2f(250.0, 140.0));
-    path.close_path();
-    canvas.stroke_path(path);
-
-    // Render the canvas to screen.
-    let mut scene = SceneProxy::from_scene(canvas.into_canvas().into_scene(),
-                                           renderer.mode().level,
-                                           RayonExecutor);
-    scene.build_and_render(&mut renderer, BuildOptions::default());
-
-    // Present the surface.
-    let mut surface = device.unbind_surface_from_context(&mut context).unwrap().unwrap();
-    device.present_surface(&mut context, &mut surface).unwrap();
-    device.bind_surface_to_context(&mut context, surface).unwrap();
-
+    let mut is_first_render = true;
     // Wait for a keypress.
     event_loop.run_forever(|event| {
+        let mut should_render = is_first_render;
         match event {
             Event::WindowEvent { event: WindowEvent::CloseRequested, .. } |
-            Event::WindowEvent { event: WindowEvent::KeyboardInput { .. }, .. } => {
-                ControlFlow::Break
+            Event::WindowEvent { event: WindowEvent::KeyboardInput { .. }, .. } => return ControlFlow::Break,
+            Event::WindowEvent { event: WindowEvent::Refresh, .. } => {
+                should_render = true;
             }
-            _ => ControlFlow::Continue,
+            _ => {},
         }
+
+        if should_render {
+            // Make a canvas. We're going to draw a house.
+            let mut canvas = Canvas::new(framebuffer_size.to_f32()).get_context_2d(font_context.clone());
+
+            // Set line width.
+            canvas.set_line_width(10.0);
+
+            // Draw walls.
+            canvas.stroke_rect(RectF::new(vec2f(75.0, 140.0), vec2f(150.0, 110.0)));
+
+            // Draw door.
+            canvas.fill_rect(RectF::new(vec2f(130.0, 190.0), vec2f(40.0, 60.0)));
+
+            // Draw roof.
+            let mut path = Path2D::new();
+            path.move_to(vec2f(50.0, 140.0));
+            path.line_to(vec2f(150.0, 60.0));
+            path.line_to(vec2f(250.0, 140.0));
+            path.close_path();
+            canvas.stroke_path(path);
+
+            // Render the canvas to screen.
+            let mut scene = SceneProxy::from_scene(canvas.into_canvas().into_scene(),
+                                                   renderer.mode().level,
+                                                   RayonExecutor);
+            scene.build_and_render(&mut renderer, BuildOptions::default());
+
+            // Present the surface.
+            let mut surface = device.unbind_surface_from_context(&mut context).unwrap().unwrap();
+            device.present_surface(&mut context, &mut surface).unwrap();
+            device.bind_surface_to_context(&mut context, surface).unwrap();
+        }
+
+        is_first_render = false;
+        ControlFlow::Continue
     });
 
     // Clean up.