spinner showing pending background work

Author: Stephan Dilly

asyncgit/src/diff.rs

@@ -3,7 +3,10 @@ use crossbeam_channel::Sender;
 use log::trace;
 use std::{
     hash::Hash,
-    sync::{Arc, Mutex},
+    sync::{
+        atomic::{AtomicUsize, Ordering},
+        Arc, Mutex,
+    },
 };
 
 ///
@@ -24,6 +27,7 @@ pub struct AsyncDiff {
     current: Arc<Mutex<Request<u64, FileDiff>>>,
     last: Arc<Mutex<Option<LastResult<DiffParams, FileDiff>>>>,
     sender: Sender<AsyncNotification>,
+    pending: Arc<AtomicUsize>,
 }
 
 impl AsyncDiff {
@@ -33,6 +37,7 @@ impl AsyncDiff {
             current: Arc::new(Mutex::new(Request(0, None))),
             last: Arc::new(Mutex::new(None)),
             sender,
+            pending: Arc::new(AtomicUsize::new(0)),
         }
     }
 
@@ -54,6 +59,11 @@ impl AsyncDiff {
         }
     }
 
+    ///
+    pub fn is_pending(&self) -> bool {
+        self.pending.load(Ordering::Relaxed) > 0
+    }
+
     ///
     pub fn request(
         &mut self,
@@ -77,7 +87,10 @@ impl AsyncDiff {
         let arc_current = Arc::clone(&self.current);
         let arc_last = Arc::clone(&self.last);
         let sender = self.sender.clone();
+        let arc_pending = Arc::clone(&self.pending);
         rayon_core::spawn(move || {
+            arc_pending.fetch_add(1, Ordering::Relaxed);
+
             let res =
                 sync::diff::get_diff(CWD, params.0.clone(), params.1);
             let mut notify = false;
@@ -98,6 +111,8 @@ impl AsyncDiff {
                 });
             }
 
+            arc_pending.fetch_sub(1, Ordering::Relaxed);
+
             if notify {
                 sender
                     .send(AsyncNotification::Diff)

src/app.rs

@@ -229,12 +229,9 @@ impl App {
         self.do_quit
     }
 
-    fn can_focus_diff(&self) -> bool {
-        match self.focus {
-            Focus::WorkDir => self.index_wd.is_file_seleted(),
-            Focus::Stage => self.index.is_file_seleted(),
-            _ => false,
-        }
+    ///
+    pub fn any_work_pending(&self) -> bool {
+        self.git_diff.is_pending()
     }
 }
 
@@ -278,6 +275,14 @@ impl App {
         None
     }
 
+    fn can_focus_diff(&self) -> bool {
+        match self.focus {
+            Focus::WorkDir => self.index_wd.is_file_seleted(),
+            Focus::Stage => self.index.is_file_seleted(),
+            _ => false,
+        }
+    }
+
     fn update_commands(&mut self) {
         self.help.set_cmds(self.commands(true));
         self.current_commands = self.commands(false);

src/main.rs

@@ -8,6 +8,7 @@ mod components;
 mod keys;
 mod poll;
 mod queue;
+mod spinner;
 mod strings;
 mod ui;
 mod version;
@@ -28,6 +29,7 @@ use log::error;
 use scopeguard::defer;
 use scopetime::scope_time;
 use simplelog::{Config, LevelFilter, WriteLogger};
+use spinner::Spinner;
 use std::{
     env, fs,
     fs::File,
@@ -40,6 +42,7 @@ use tui::{
 };
 
 static TICK_INTERVAL: Duration = Duration::from_secs(5);
+static SPINNER_INTERVAL: Duration = Duration::from_millis(50);
 
 fn main() -> Result<()> {
     setup_logging();
@@ -65,28 +68,44 @@ fn main() -> Result<()> {
     set_panic_handlers();
 
     let rx_input = poll::start_polling_thread();
-
     let ticker = tick(TICK_INTERVAL);
+    let spinner_ticker = tick(SPINNER_INTERVAL);
 
     app.update();
     draw(&mut terminal, &mut app)?;
 
+    let mut spinner = Spinner::default();
+
     loop {
-        let events: Vec<QueueEvent> =
-            select_event(&rx_input, &rx_git, &ticker);
+        let events: Vec<QueueEvent> = select_event(
+            &rx_input,
+            &rx_git,
+            &ticker,
+            &spinner_ticker,
+        );
 
         {
             scope_time!("loop");
 
+            let mut needs_draw = true;
+
             for e in events {
                 match e {
                     QueueEvent::InputEvent(ev) => app.event(ev),
                     QueueEvent::Tick => app.update(),
                     QueueEvent::GitEvent(ev) => app.update_git(ev),
+                    QueueEvent::SpinnerUpdate => {
+                        needs_draw = false;
+                        spinner.update()
+                    }
                 }
             }
 
-            draw(&mut terminal, &mut app)?;
+            if needs_draw {
+                draw(&mut terminal, &mut app)?;
+            }
+
+            spinner.draw(&mut terminal, app.any_work_pending())?;
 
             if app.is_quit() {
                 break;
@@ -112,6 +131,7 @@ fn select_event(
     rx_input: &Receiver<Vec<QueueEvent>>,
     rx_git: &Receiver<AsyncNotification>,
     rx_ticker: &Receiver<Instant>,
+    rx_spinner: &Receiver<Instant>,
 ) -> Vec<QueueEvent> {
     let mut events: Vec<QueueEvent> = Vec::new();
 
@@ -120,6 +140,7 @@ fn select_event(
     sel.recv(rx_input);
     sel.recv(rx_git);
     sel.recv(rx_ticker);
+    sel.recv(rx_spinner);
 
     let oper = sel.select();
     let index = oper.index();
@@ -132,7 +153,10 @@ fn select_event(
         2 => oper
             .recv(rx_ticker)
             .map(|_| events.push(QueueEvent::Tick)),
-        _ => Ok(()),
+        3 => oper
+            .recv(rx_spinner)
+            .map(|_| events.push(QueueEvent::SpinnerUpdate)),
+        _ => panic!("unknown select source"),
     }
     .unwrap();
 

src/poll.rs

@@ -7,6 +7,7 @@ use std::time::{Duration, Instant};
 #[derive(Clone, Copy)]
 pub enum QueueEvent {
     Tick,
+    SpinnerUpdate,
     GitEvent(AsyncNotification),
     InputEvent(Event),
 }

src/spinner.rs

@@ -0,0 +1,36 @@
+use std::io;
+use tui::{backend::Backend, buffer::Cell, Terminal};
+
+static SPINNER_CHARS: &[char] = &['|', '/', '-', '\\'];
+
+///
+#[derive(Default)]
+pub struct Spinner {
+    idx: usize,
+}
+
+impl Spinner {
+    ///
+    pub fn update(&mut self) {
+        self.idx += 1;
+        self.idx %= SPINNER_CHARS.len();
+    }
+
+    pub fn draw<B: Backend>(
+        &self,
+        terminal: &mut Terminal<B>,
+        pending: bool,
+    ) -> io::Result<()> {
+        let idx = self.idx;
+
+        let c: Cell = Cell::default()
+            .set_char(if pending { SPINNER_CHARS[idx] } else { ' ' })
+            .clone();
+        terminal
+            .backend_mut()
+            .draw(vec![(0_u16, 0_u16, &c)].into_iter())?;
+        tui::backend::Backend::flush(terminal.backend_mut())?;
+
+        Ok(())
+    }
+}