Merge #1822

1822: Switch from .run_forever() to .poll_events() in gfx_app r=kvark a=jturner314

This commit uses `.poll_events()` to allow processing multiple events per rendered frame. (Before, only one event was processed per frame.) This is necessary because it's easy for the user to generate events much faster than frames can be rendered (e.g. by moving the mouse).

Additionally, with `.run_forever()`, rendering blocked on receiving events. (An event had to occur before a frame was rendered.) In order to see an animation such as the `particle` example, the user had to generate events fast enough to cause frames to be rendered (e.g. by moving the mouse over the window).

See also rust-windowing/winit#276 and rust-windowing/winit#231

PR checklist:
- [ ] `make` succeeds (on *nix)
  I don't see a Makefile. `make` says `make: *** No targets specified and no makefile found.  Stop.`
- [ ] `make reftests` succeeds
  I don't see a Makefile. I did run `cargo test`, though, and that succeeded (although it ran only 3 tests).
- [X] tested examples with the following backends:
  When I run `glxinfo`, I see `OpenGL core profile version string: 3.3 (Core Profile) Mesa 17.3.3`. I tested all of the examples. They all worked correctly, except `terrain_tessellated` (which failed to build even before this commit) and `triangle` (which still has the `.run_forever()` issue since it doesn't use `gfx_app`).

src/lib.rs

@@ -148,43 +148,45 @@ A: Sized + ApplicationBase<gfx_device_gl::Resources, gfx_device_gl::CommandBuffe
     });
 
     let mut harness = Harness::new();
-    events_loop.run_forever(move |event| {
-        use glutin::ControlFlow;
-
-        if let winit::Event::WindowEvent { event, .. } = event {
-            match event {
-                winit::WindowEvent::Closed => return ControlFlow::Break,
-                winit::WindowEvent::KeyboardInput {
-                    input: winit::KeyboardInput {
-                        state: winit::ElementState::Pressed,
-                        virtual_keycode: key,
+    let mut running = true;
+    while running {
+        events_loop.poll_events(|event| {
+            if let winit::Event::WindowEvent { event, .. } = event {
+                match event {
+                    winit::WindowEvent::Closed => running = false,
+                    winit::WindowEvent::KeyboardInput {
+                        input: winit::KeyboardInput {
+                            state: winit::ElementState::Pressed,
+                            virtual_keycode: key,
+                            ..
+                        },
                         ..
+                    } if key == A::get_exit_key() => running = false,
+                    winit::WindowEvent::Resized(width, height) => {
+                        if width != cur_width || height != cur_height {
+                            window.resize(width, height);
+                            cur_width = width;
+                            cur_height = height;
+                            let (new_color, new_depth) = gfx_window_glutin::new_views(&window);
+                            app.on_resize(&mut factory, WindowTargets {
+                                color: new_color,
+                                depth: new_depth,
+                                aspect_ratio: width as f32 / height as f32,
+                            });
+                        }
                     },
-                    ..
-                } if key == A::get_exit_key() => return ControlFlow::Break,
-                winit::WindowEvent::Resized(width, height) => if width != cur_width || height != cur_height {
-                    window.resize(width, height);
-                    cur_width = width;
-                    cur_height = height;
-                    let (new_color, new_depth) = gfx_window_glutin::new_views(&window);
-                    app.on_resize(&mut factory, WindowTargets {
-                        color: new_color,
-                        depth: new_depth,
-                        aspect_ratio: width as f32 / height as f32,
-                    });
-                },
-                _ => app.on(event),
+                    _ => app.on(event),
+                }
             }
-        }
+        });
 
         // draw a frame
         app.render(&mut device);
         window.swap_buffers().unwrap();
         device.cleanup();
 
         harness.bump();
-        ControlFlow::Continue
-    });
+    }
 }