optimize all async job related clones away (#725)

Author: Stephan Dilly

async_utils/src/lib.rs

@@ -66,10 +66,10 @@ impl<J: 'static + AsyncJob, T: Copy + Send + 'static>
         false
     }
 
-    /// return clone of last result
-    pub fn get_last(&self) -> Option<J> {
-        if let Ok(last) = self.last.lock() {
-            last.clone()
+    ///
+    pub fn take_last(&self) -> Option<J> {
+        if let Ok(mut last) = self.last.lock() {
+            last.take()
         } else {
             None
         }

src/components/revision_files.rs

@@ -173,11 +173,7 @@ impl RevisionFilesComponent {
         }
     }
 
-    fn draw_tree<B: Backend>(
-        &self,
-        f: &mut Frame<B>,
-        area: Rect,
-    ) -> Result<()> {
+    fn draw_tree<B: Backend>(&self, f: &mut Frame<B>, area: Rect) {
         let tree_height = usize::from(area.height.saturating_sub(2));
 
         let selection = self.tree.visual_selection();
@@ -203,18 +199,6 @@ impl RevisionFilesComponent {
                 Self::tree_item_to_span(item, &self.theme, selected)
             });
 
-        f.render_widget(Clear, area);
-        f.render_widget(
-            Block::default()
-                .borders(Borders::TOP)
-                .title(Span::styled(
-                    format!(" {}", self.title),
-                    self.theme.title(true),
-                ))
-                .border_style(self.theme.block(true)),
-            area,
-        );
-
         let is_tree_focused = matches!(self.focus, Focus::Tree);
 
         ui::draw_list_block(
@@ -235,8 +219,6 @@ impl RevisionFilesComponent {
                 self.scroll_top.get(),
             );
         }
-
-        Ok(())
     }
 }
 
@@ -259,7 +241,19 @@ impl DrawableComponent for RevisionFilesComponent {
                 )
                 .split(area);
 
-            self.draw_tree(f, chunks[0])?;
+            f.render_widget(Clear, area);
+            f.render_widget(
+                Block::default()
+                    .borders(Borders::TOP)
+                    .title(Span::styled(
+                        format!(" {}", self.title),
+                        self.theme.title(true),
+                    ))
+                    .border_style(self.theme.block(true)),
+                area,
+            );
+
+            self.draw_tree(f, chunks[0]);
 
             self.current_file.draw(f, chunks[1])?;
         }

src/components/syntax_text.rs

@@ -61,11 +61,11 @@ impl SyntaxTextComponent {
     ///
     pub fn update(&mut self, ev: AsyncNotification) {
         if ev == AsyncNotification::SyntaxHighlighting {
-            if let Some(job) = self.async_highlighting.get_last() {
+            if let Some(job) = self.async_highlighting.take_last() {
                 if let Some((path, content)) =
                     self.current_file.as_mut()
                 {
-                    if let Some(syntax) = (*job.text).clone() {
+                    if let Some(syntax) = job.result() {
                         if syntax.path() == Path::new(path) {
                             *content = Either::Left(syntax);
                         }

src/ui/syntax_text.rs

@@ -5,7 +5,7 @@ use std::{
     ffi::OsStr,
     ops::Range,
     path::{Path, PathBuf},
-    sync::Arc,
+    sync::{Arc, Mutex},
 };
 use syntect::{
     highlighting::{
@@ -145,27 +145,50 @@ fn syntact_style_to_tui(style: &Style) -> tui::style::Style {
     res
 }
 
+enum JobState {
+    Request((String, String)),
+    Response(SyntaxText),
+}
+
 #[derive(Clone, Default)]
 pub struct AsyncSyntaxJob {
-    //TODO: can we merge input and text into a single enum to represent the state transition?
-    pub input: Option<(String, String)>,
-    pub text: Arc<Option<SyntaxText>>,
+    state: Arc<Mutex<Option<JobState>>>,
 }
 
 impl AsyncSyntaxJob {
     pub fn new(content: String, path: String) -> Self {
         Self {
-            input: Some((content, path)),
-            text: Arc::new(None),
+            state: Arc::new(Mutex::new(Some(JobState::Request((
+                content, path,
+            ))))),
+        }
+    }
+
+    pub fn result(&self) -> Option<SyntaxText> {
+        if let Ok(mut state) = self.state.lock() {
+            if let Some(state) = state.take() {
+                return match state {
+                    JobState::Request(_) => None,
+                    JobState::Response(text) => Some(text),
+                };
+            }
         }
+
+        None
     }
 }
 
 impl AsyncJob for AsyncSyntaxJob {
     fn run(&mut self) {
-        if let Some((text, path)) = self.input.take() {
-            let syntax = SyntaxText::new(text, Path::new(&path));
-            self.text = Arc::new(Some(syntax));
+        if let Ok(mut state) = self.state.lock() {
+            *state = state.take().map(|state| match state {
+                JobState::Request((content, path)) => {
+                    let syntax =
+                        SyntaxText::new(content, Path::new(&path));
+                    JobState::Response(syntax)
+                }
+                JobState::Response(res) => JobState::Response(res),
+            });
         }
     }
 }