tui: Allow toggling mouse capture at runtime (#6675)

This picks up changes to the `editor.mouse` option at runtime - either
through `:set-option` or `:config-reload`. When the value changes, we
tell the terminal to enable or disable mouse capture sequences.

helix-tui/src/backend/crossterm.rs

@@ -63,6 +63,7 @@ pub struct CrosstermBackend<W: Write> {
     buffer: W,
     capabilities: Capabilities,
     supports_keyboard_enhancement_protocol: OnceCell<bool>,
+    mouse_capture_enabled: bool,
 }
 
 impl<W> CrosstermBackend<W>
@@ -74,6 +75,7 @@ where
             buffer,
             capabilities: Capabilities::from_env_or_default(config),
             supports_keyboard_enhancement_protocol: OnceCell::new(),
+            mouse_capture_enabled: false,
         }
     }
 
@@ -123,6 +125,7 @@ where
         execute!(self.buffer, terminal::Clear(terminal::ClearType::All))?;
         if config.enable_mouse_capture {
             execute!(self.buffer, EnableMouseCapture)?;
+            self.mouse_capture_enabled = true;
         }
         if self.supports_keyboard_enhancement_protocol() {
             execute!(
@@ -136,6 +139,19 @@ where
         Ok(())
     }
 
+    fn reconfigure(&mut self, config: Config) -> io::Result<()> {
+        if self.mouse_capture_enabled != config.enable_mouse_capture {
+            if config.enable_mouse_capture {
+                execute!(self.buffer, EnableMouseCapture)?;
+            } else {
+                execute!(self.buffer, DisableMouseCapture)?;
+            }
+            self.mouse_capture_enabled = config.enable_mouse_capture;
+        }
+
+        Ok(())
+    }
+
     fn restore(&mut self, config: Config) -> io::Result<()> {
         // reset cursor shape
         write!(self.buffer, "\x1B[0 q")?;

helix-tui/src/backend/mod.rs

@@ -14,6 +14,7 @@ pub use self::test::TestBackend;
 
 pub trait Backend {
     fn claim(&mut self, config: Config) -> Result<(), io::Error>;
+    fn reconfigure(&mut self, config: Config) -> Result<(), io::Error>;
     fn restore(&mut self, config: Config) -> Result<(), io::Error>;
     fn force_restore() -> Result<(), io::Error>;
     fn draw<'a, I>(&mut self, content: I) -> Result<(), io::Error>

helix-tui/src/backend/test.rs

@@ -111,6 +111,10 @@ impl Backend for TestBackend {
         Ok(())
     }
 
+    fn reconfigure(&mut self, _config: Config) -> Result<(), io::Error> {
+        Ok(())
+    }
+
     fn restore(&mut self, _config: Config) -> Result<(), io::Error> {
         Ok(())
     }

helix-tui/src/terminal.rs

@@ -116,6 +116,10 @@ where
         self.backend.claim(config)
     }
 
+    pub fn reconfigure(&mut self, config: Config) -> io::Result<()> {
+        self.backend.reconfigure(config)
+    }
+
     pub fn restore(&mut self, config: Config) -> io::Result<()> {
         self.backend.restore(config)
     }