Don't visually freeze the UI on an onslaught of input.

Cargo.lock

@@ -10,6 +10,7 @@ dependencies = [
  "gag",
  "ropey",
  "smallvec 1.2.0",
+ "time",
  "unicode-segmentation",
  "unicode-width",
 ]
@@ -291,6 +292,35 @@ version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "74490b50b9fbe561ac330df47c08f3f33073d2d00c150f719147d7c54522fa1b"
 
+[[package]]
+name = "proc-macro-hack"
+version = "0.5.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ecd45702f76d6d3c75a80564378ae228a85f0b59d2f3ed43c91b4a69eb2ebfc5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3acb317c6ff86a4e579dfa00fc5e6cca91ecbb4e7eb2df0468805b674eb88548"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "rand"
 version = "0.7.3"
@@ -356,6 +386,17 @@ dependencies = [
  "smallvec 0.6.13",
 ]
 
+[[package]]
+name = "rustversion"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3bba175698996010c4f6dce5e7f173b6eb781fce25d2cfc45e27091ce0b79f6"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "scopeguard"
 version = "1.0.0"
@@ -410,6 +451,17 @@ version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
 
+[[package]]
+name = "syn"
+version = "1.0.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af6f3550d8dff9ef7dc34d384ac6f107e5d31c8f57d9f28e0081503f547ac8f5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
 [[package]]
 name = "tempfile"
 version = "3.1.0"
@@ -433,6 +485,38 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "time"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bcb8742444475438c500d017736dd7cf3d9c9dd1f0153cfa4af428692484e3ef"
+dependencies = [
+ "rustversion",
+ "time-macros",
+]
+
+[[package]]
+name = "time-macros"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ae9b6e9f095bc105e183e3cd493d72579be3181ad4004fceb01adbe9eecab2d"
+dependencies = [
+ "proc-macro-hack",
+ "time-macros-impl",
+]
+
+[[package]]
+name = "time-macros-impl"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e987cfe0537f575b5fc99909de6185f6c19c3ad8889e2275e686a873d0869ba1"
+dependencies = [
+ "proc-macro-hack",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "unicode-segmentation"
 version = "1.6.0"
@@ -445,6 +529,12 @@ version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "caaa9d531767d1ff2150b9332433f32a24622147e5ebb1f26409d5da67afd479"
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
+
 [[package]]
 name = "vec_map"
 version = "0.8.1"

Cargo.toml

@@ -23,6 +23,7 @@ clap = "2"
 smallvec = "1"
 crossterm = "0.14"
 gag = "0.1.10"
+time = "0.2"
 
 # Local crate dependencies
 [dependencies.backend]

src/term_ui/mod.rs

@@ -15,7 +15,7 @@ use crate::{
     editor::Editor,
     formatter::{block_count, block_index_and_range, char_range_from_block_index, LineFormatter},
     string_utils::{line_ending_to_str, rope_slice_is_line_ending, LineEnding},
-    utils::{digit_count, RopeGraphemes},
+    utils::{digit_count, RopeGraphemes, Timer},
 };
 
 use self::{
@@ -24,6 +24,7 @@ use self::{
 };
 
 const EMPTY_MOD: KeyModifiers = KeyModifiers::empty();
+const UPDATE_TICK_MS: u64 = 10;
 
 // Color theme.
 // Styles are (FG, BG).
@@ -80,6 +81,7 @@ const STYLE_INFO: Style = Style(
 macro_rules! ui_loop {
     ($term_ui:ident,draw $draw:block,key_press($key:ident) $key_press:block) => {
         let mut stop = false;
+        let mut timer = Timer::new();
 
         // Draw the editor to screen for the first time
         {
@@ -97,7 +99,7 @@ macro_rules! ui_loop {
             // want to re-draw on e.g. async syntax highlighting updates, or
             // update based on a file being modified outside our process.
             loop {
-                if crossterm::event::poll(Duration::from_millis(5)).unwrap() {
+                if crossterm::event::poll(Duration::from_millis(UPDATE_TICK_MS)).unwrap() {
                     match crossterm::event::read().unwrap() {
                         Event::Key($key) => {
                             let (status, state_changed) = || -> (LoopStatus, bool) { $key_press }();
@@ -120,6 +122,15 @@ macro_rules! ui_loop {
                             break;
                         }
                     }
+
+                    // If too much time has passed since the last redraw,
+                    // break so we can draw if needed.  This keeps an onslaught
+                    // of input (e.g. when pasting a large piece of text) from
+                    // visually freezing the UI.
+                    if timer.elapsed() >= UPDATE_TICK_MS {
+                        timer.tick();
+                        break;
+                    }
                 } else {
                     break;
                 }

src/utils.rs

@@ -1,4 +1,5 @@
 use ropey::{iter::Chunks, str_utils::byte_to_char_idx, RopeSlice};
+use time::Instant;
 use unicode_segmentation::{GraphemeCursor, GraphemeIncomplete};
 use unicode_width::UnicodeWidthStr;
 
@@ -190,6 +191,34 @@ impl<'a> Iterator for RopeGraphemes<'a> {
 
 //=============================================================
 
+#[derive(Copy, Clone)]
+pub struct Timer {
+    last_instant: Instant,
+}
+
+impl Timer {
+    pub fn new() -> Timer {
+        Timer {
+            last_instant: Instant::now(),
+        }
+    }
+
+    /// Marks a new tick time and returns the time elapsed in milliseconds since
+    /// the last call to tick().
+    pub fn tick(&mut self) -> u64 {
+        let n = self.elapsed();
+        self.last_instant = Instant::now();
+        n
+    }
+
+    /// Returns the time elapsed in milliseconds since the last call to tick().
+    pub fn elapsed(self) -> u64 {
+        self.last_instant.elapsed().whole_milliseconds() as u64
+    }
+}
+
+//=============================================================
+
 #[cfg(test)]
 mod tests {
     use super::*;