Avoid asking for terminal size on each rendering

Author: mo8it

src/watch.rs

@@ -29,7 +29,7 @@ mod terminal_event;
 enum WatchEvent {
     Input(InputEvent),
     FileChange { exercise_ind: usize },
-    TerminalResize,
+    TerminalResize { width: u16 },
     NotifyErr(notify::Error),
     TerminalEventErr(io::Error),
 }
@@ -72,7 +72,7 @@ fn run_watch(
         None
     };
 
-    let mut watch_state = WatchState::new(app_state, manual_run);
+    let mut watch_state = WatchState::build(app_state, manual_run)?;
 
     let mut stdout = io::stdout().lock();
     watch_state.run_current_exercise(&mut stdout)?;
@@ -96,7 +96,9 @@ fn run_watch(
             WatchEvent::FileChange { exercise_ind } => {
                 watch_state.handle_file_change(exercise_ind, &mut stdout)?;
             }
-            WatchEvent::TerminalResize => watch_state.render(&mut stdout)?,
+            WatchEvent::TerminalResize { width } => {
+                watch_state.update_term_width(width, &mut stdout)?;
+            }
             WatchEvent::NotifyErr(e) => return Err(Error::from(e).context(NOTIFY_ERR)),
             WatchEvent::TerminalEventErr(e) => {
                 return Err(Error::from(e).context("Terminal event listener failed"));

src/watch/state.rs

@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{Context, Result};
 use crossterm::{
     style::{
         Attribute, Attributes, Color, ResetColor, SetAttribute, SetAttributes, SetForegroundColor,
@@ -27,17 +27,23 @@ pub struct WatchState<'a> {
     show_hint: bool,
     done_status: DoneStatus,
     manual_run: bool,
+    term_width: u16,
 }
 
 impl<'a> WatchState<'a> {
-    pub fn new(app_state: &'a mut AppState, manual_run: bool) -> Self {
-        Self {
+    pub fn build(app_state: &'a mut AppState, manual_run: bool) -> Result<Self> {
+        let term_width = terminal::size()
+            .context("Failed to get the terminal size")?
+            .0;
+
+        Ok(Self {
             app_state,
             output: Vec::with_capacity(OUTPUT_CAPACITY),
             show_hint: false,
             done_status: DoneStatus::Pending,
             manual_run,
-        }
+            term_width,
+        })
     }
 
     pub fn run_current_exercise(&mut self, stdout: &mut StdoutLock) -> Result<()> {
@@ -175,12 +181,11 @@ impl<'a> WatchState<'a> {
             )?;
         }
 
-        let line_width = terminal::size()?.0;
         progress_bar(
             stdout,
             self.app_state.n_done(),
             self.app_state.exercises().len() as u16,
-            line_width,
+            self.term_width,
         )?;
 
         stdout.write_all(b"\nCurrent exercise: ")?;
@@ -202,4 +207,13 @@ impl<'a> WatchState<'a> {
 
         Ok(())
     }
+
+    pub fn update_term_width(&mut self, width: u16, stdout: &mut StdoutLock) -> io::Result<()> {
+        if self.term_width != width {
+            self.term_width = width;
+            self.render(stdout)?;
+        }
+
+        Ok(())
+    }
 }

src/watch/terminal_event.rs

@@ -43,8 +43,8 @@ pub fn terminal_event_handler(tx: Sender<WatchEvent>, manual_run: bool) {
                     return;
                 }
             }
-            Event::Resize(_, _) => {
-                if tx.send(WatchEvent::TerminalResize).is_err() {
+            Event::Resize(width, _) => {
+                if tx.send(WatchEvent::TerminalResize { width }).is_err() {
                     return;
                 }
             }