Add event polling to Blt backend

Basically simulates a constant set_fps(30)

src/backend/blt.rs

@@ -15,7 +15,7 @@ use std::collections::HashSet;
 use theme::{BaseColor, Color, ColorPair, Effect};
 use vec::Vec2;
 use chan;
-use std::thread;
+use std::time::{Duration, Instant};
 
 enum ColorRole {
     Foreground,
@@ -23,28 +23,38 @@ enum ColorRole {
 }
 
 pub struct Backend {
-}
-
-struct InputParser {
-    event_sink: chan::Sender<Event>,
     buttons_pressed: HashSet<MouseButton>,
     mouse_position: Vec2,
 }
 
-impl InputParser {
+impl Backend {
-    fn new(event_sink: chan::Sender<Event>) -> Self {
+    pub fn init() -> Box<backend::Backend> {
-        InputParser {
+        terminal::open("Cursive", 80, 24);
-            event_sink,
+        terminal::set(terminal::config::Window::empty().resizeable(true));
+        terminal::set(vec![
+            terminal::config::InputFilter::Group {
+                group: terminal::config::InputFilterGroup::Keyboard,
+                both: false,
+            },
+            terminal::config::InputFilter::Group {
+                group: terminal::config::InputFilterGroup::Mouse,
+                both: true,
+            },
+        ]);
+
+        let c = Backend {
             buttons_pressed: HashSet::new(),
             mouse_position: Vec2::zero(),
-        }
+        };
+
+        Box::new(c)
     }
 
-    fn parse_next(&mut self) {
+    fn parse_next(&mut self) -> Option<Event> {
 
         // TODO: we could add backend-specific controls here.
         // Ex: ctrl+mouse wheel cause window cellsize to change
-        let event = if let Some(ev) = terminal::wait_event() {
+        terminal::read_event().map(|ev| {
             match ev {
                 BltEvent::Close => Event::Exit,
                 BltEvent::Resize { .. } => Event::WindowResize,
@@ -94,10 +104,7 @@ impl InputParser {
                     Event::Refresh
                 }
             }
-        } else {
+        })
-            Event::Refresh
-        };
-        self.event_sink.send(event);
     }
 
     fn blt_keycode_to_ev(
@@ -223,28 +230,6 @@ impl InputParser {
     }
 }
 
-impl Backend {
-    pub fn init() -> Box<backend::Backend> {
-        terminal::open("Cursive", 80, 24);
-        terminal::set(terminal::config::Window::empty().resizeable(true));
-        terminal::set(vec![
-            terminal::config::InputFilter::Group {
-                group: terminal::config::InputFilterGroup::Keyboard,
-                both: false,
-            },
-            terminal::config::InputFilter::Group {
-                group: terminal::config::InputFilterGroup::Mouse,
-                both: true,
-            },
-        ]);
-
-        let c = Backend {};
-
-        Box::new(c)
-    }
-
-}
-
 impl backend::Backend for Backend {
     fn finish(&mut self) {
         terminal::close();
@@ -320,14 +305,19 @@ impl backend::Backend for Backend {
         terminal::print_xy(pos.x as i32, pos.y as i32, text);
     }
 
-    fn start_input_thread(&mut self, event_sink: chan::Sender<Event>) {
+    fn start_input_thread(&mut self, _event_sink: chan::Sender<Event>) {
-        let mut parser = InputParser::new(event_sink);
-
-        thread::spawn(move || {
-            loop {
-                parser.parse_next();
     }
-        });
+
+    fn prepare_input(&mut self, event_sink: &chan::Sender<Event>, timeout: Duration) {
+        // Wait for up to `timeout_ms`.
+        let start = Instant::now();
+        while start.elapsed() < timeout {
+            if let Some(event) = self.parse_next() {
+                event_sink.send(event);
+                return;
+            }
+        }
+        event_sink.send(Event::Refresh);
     }
 }
 

src/backend/dummy.rs

@@ -4,7 +4,7 @@ use theme;
 use event;
 use vec::Vec2;
 
-use std::thread;
+use std::time::Duration;
 
 use chan;
 
@@ -32,8 +32,11 @@ impl backend::Backend for Backend {
         (1, 1).into()
     }
 
-    fn start_input_thread(&mut self, event_sink: chan::Sender<event::Event>) {
+    fn start_input_thread(&mut self, _event_sink: chan::Sender<event::Event>) {
-        thread::spawn(move || event_sink.send(event::Event::Exit));
+    }
+
+    fn prepare_input(&mut self, event_sink: &chan::Sender<event::Event>, _timeout: Duration) {
+        event_sink.send(event::Event::Exit)
     }
 
     fn print_at(&self, _: Vec2, _: &str) {}

src/backend/mod.rs

@@ -14,6 +14,8 @@ use chan::Sender;
 
 use vec::Vec2;
 
+use std::time::Duration;
+
 pub mod dummy;
 
 pub mod termion;
@@ -29,8 +31,20 @@ pub trait Backend {
     /// This should clear any state in the terminal.
     fn finish(&mut self);
 
+    /// Starts a thread to collect input and send it to the given channel.
     fn start_input_thread(&mut self, event_sink: Sender<event::Event>);
 
+    /// Prepares the backend to collect input.
+    ///
+    /// This is only required for non-thread-safe backends like BearLibTerminal
+    /// where we cannot collect input in a separate thread.
+    fn prepare_input(&mut self, event_sink: &Sender<event::Event>, timeout: Duration) {
+        // Dummy implementation for most backends.
+        // Little trick to avoid unused variables.
+        let _ = event_sink;
+        let _ = timeout;
+    }
+
     /// Refresh the screen.
     fn refresh(&mut self);
 
@@ -40,9 +54,6 @@ pub trait Backend {
     /// Returns the screen size.
     fn screen_size(&self) -> Vec2;
 
-    // /// Gets a receiver for input events.
-    // fn event_receiver(&mut self) -> Receiver<event::Event>;
-
     /// Main method used for printing
     fn print_at(&self, pos: Vec2, text: &str);
 

src/cursive.rs

@@ -5,6 +5,7 @@ use event::{Callback, Event, EventResult};
 use printer::Printer;
 use std::any::Any;
 use std::collections::HashMap;
+use std::time::Duration;
 use std::path::Path;
 use theme;
 use vec::Vec2;
@@ -40,6 +41,7 @@ pub struct Cursive {
     cb_sink: chan::Sender<Box<CbFunc>>,
 
     event_source: chan::Receiver<Event>,
+    event_sink: chan::Sender<Event>,
 }
 
 /// Describes one of the possible interruptions we should handle.
@@ -122,7 +124,7 @@ impl Cursive {
         let (cb_sink, cb_source) = chan::async();
         let (event_sink, event_source) = chan::async();
 
-        backend.start_input_thread(event_sink);
+        backend.start_input_thread(event_sink.clone());
 
         Cursive {
             fps: 0,
@@ -136,6 +138,7 @@ impl Cursive {
             cb_source,
             cb_sink,
             event_source,
+            event_sink,
             backend: backend,
         }
     }
@@ -573,6 +576,8 @@ impl Cursive {
         let input_channel = &self.event_source;
         let cb_channel = &self.cb_source;
 
+        self.backend.prepare_input(&self.event_sink, Duration::from_millis(30));
+
         if self.fps > 0 {
             let timeout =  1000 / self.fps;
             let timeout = chan::after_ms(timeout);