Invert control flow.

There's an issue whereby if keys are held down in the 3D mode it doesn't keep
redrawing. This will be fixed in a followup.

demo/common/src/lib.rs

@@ -79,7 +79,8 @@ mod device;
 mod ui;
 
 pub struct DemoApp<W> where W: Window {
-    window: W,
+    pub window: W,
+    pub should_exit: bool,
 
     scale_factor: f32,
 
@@ -88,9 +89,7 @@ pub struct DemoApp<W> where W: Window {
 
     camera: Camera,
     frame_counter: u32,
-    events: Vec<Event>,
     pending_screenshot_path: Option<PathBuf>,
-    exit: bool,
     mouselook_enabled: bool,
     dirty: bool,
     expire_message_event_id: u32,
@@ -147,6 +146,7 @@ impl<W> DemoApp<W> where W: Window {
 
         DemoApp {
             window,
+            should_exit: false,
 
             scale_factor: drawable_size.x() as f32 / window_size.x() as f32,
 
@@ -156,8 +156,6 @@ impl<W> DemoApp<W> where W: Window {
             camera,
             frame_counter: 0,
             pending_screenshot_path: None,
-            events: vec![],
-            exit: false,
             mouselook_enabled: false,
             dirty: true,
             expire_message_event_id,
@@ -173,20 +171,17 @@ impl<W> DemoApp<W> where W: Window {
         }
     }
 
-    pub fn run(&mut self) {
-        while !self.exit {
+    pub fn run_once(&mut self, events: Vec<Event>) {
         // Update the scene.
         self.build_scene();
 
         // Handle events.
-            // FIXME(pcwalton): This can cause us to miss UI events if things get backed up...
-            let ui_event = self.handle_events();
+        let ui_event = self.handle_events(events);
 
         // Draw the scene.
         let render_msg = self.scene_thread_proxy.receiver.recv().unwrap();
         self.draw_scene(render_msg, ui_event);
     }
-    }
 
     fn build_scene(&mut self) {
         let drawable_size = self.window.drawable_size();
@@ -219,24 +214,15 @@ impl<W> DemoApp<W> where W: Window {
         }
     }
 
-    fn handle_events(&mut self) -> UIEvent {
+    fn handle_events(&mut self, events: Vec<Event>) -> UIEvent {
         let mut ui_event = UIEvent::None;
-
-        if !self.dirty {
-            self.events.push(self.window.get_event());
-        } else {
         self.dirty = false;
-        }
 
-        while let Some(event) = self.window.try_get_event() {
-            self.events.push(event);
-        }
-
-        for event in self.events.drain(..) {
+        for event in events {
             match event {
                 Event::Quit { .. } |
                 Event::KeyDown(Keycode::Escape) => {
-                    self.exit = true;
+                    self.should_exit = true;
                     self.dirty = true;
                 }
                 Event::WindowResized => {

demo/common/src/window.rs

@@ -17,8 +17,6 @@ pub trait Window {
     fn size(&self) -> Point2DI32;
     fn drawable_size(&self) -> Point2DI32;
     fn mouse_position(&self) -> Point2DI32;
-    fn get_event(&mut self) -> Event;
-    fn try_get_event(&mut self) -> Option<Event>;
     fn present(&self);
     fn create_user_event_id(&self) -> u32;
     fn push_user_event(message_type: u32, message_data: u32);

demo/native/src/main.rs

@@ -21,7 +21,14 @@ use sdl2_sys::{SDL_Event, SDL_UserEvent};
 use std::ptr;
 
 fn main() {
-    DemoApp::<WindowImpl>::new().run();
+    let mut app = DemoApp::<WindowImpl>::new();
+    while !app.should_exit {
+        let mut events = vec![app.window.get_event()];
+        while let Some(event) = app.window.try_get_event() {
+            events.push(event);
+        }
+        app.run_once(events);
+    }
 }
 
 thread_local! {
@@ -81,24 +88,6 @@ impl Window for WindowImpl {
         Point2DI32::new(mouse_state.x(), mouse_state.y())
     }
 
-    fn get_event(&mut self) -> Event {
-        loop {
-            let sdl_event = self.event_pump.wait_event();
-            if let Some(event) = self.convert_sdl_event(sdl_event) {
-                return event;
-            }
-        }
-    }
-
-    fn try_get_event(&mut self) -> Option<Event> {
-        loop {
-            let sdl_event = self.event_pump.poll_event()?;
-            if let Some(event) = self.convert_sdl_event(sdl_event) {
-                return Some(event);
-            }
-        }
-    }
-
     fn present(&self) {
         self.window.gl_swap_window();
     }
@@ -123,6 +112,24 @@ impl Window for WindowImpl {
 }
 
 impl WindowImpl {
+    fn get_event(&mut self) -> Event {
+        loop {
+            let sdl_event = self.event_pump.wait_event();
+            if let Some(event) = self.convert_sdl_event(sdl_event) {
+                return event;
+            }
+        }
+    }
+
+    fn try_get_event(&mut self) -> Option<Event> {
+        loop {
+            let sdl_event = self.event_pump.poll_event()?;
+            if let Some(event) = self.convert_sdl_event(sdl_event) {
+                return Some(event);
+            }
+        }
+    }
+
     fn convert_sdl_event(&self, sdl_event: SDLEvent) -> Option<Event> {
         match sdl_event {
             SDLEvent::User { type_, code, .. } => {