extract tui support code to tek_tui

tui/src/tui_engine.rs

@@ -0,0 +1,65 @@
+use crate::*;
+
+pub struct Tui {
+    pub exited:  Arc<AtomicBool>,
+    pub buffer:  Buffer,
+    pub backend: CrosstermBackend<Stdout>,
+    pub area:    [u16;4], // FIXME auto resize
+}
+
+impl Engine for Tui {
+    type Unit    = u16;
+    type Size    = [Self::Unit;2];
+    type Area    = [Self::Unit;4];
+    type Input   = TuiIn;
+    type Handled = bool;
+    type Output  = TuiOut;
+    fn exited (&self) -> bool {
+        self.exited.fetch_and(true, Relaxed)
+    }
+    fn setup (&mut self) -> Usually<()> {
+        let better_panic_handler = Settings::auto().verbosity(Verbosity::Full).create_panic_handler();
+        std::panic::set_hook(Box::new(move |info: &std::panic::PanicHookInfo|{
+            stdout().execute(LeaveAlternateScreen).unwrap();
+            CrosstermBackend::new(stdout()).show_cursor().unwrap();
+            disable_raw_mode().unwrap();
+            better_panic_handler(info);
+        }));
+        stdout().execute(EnterAlternateScreen)?;
+        self.backend.hide_cursor()?;
+        enable_raw_mode().map_err(Into::into)
+    }
+    fn teardown (&mut self) -> Usually<()> {
+        stdout().execute(LeaveAlternateScreen)?;
+        self.backend.show_cursor()?;
+        disable_raw_mode().map_err(Into::into)
+    }
+}
+
+impl Tui {
+    /// Construct a new TUI engine and wrap it for shared ownership.
+    pub fn new () -> Usually<Arc<RwLock<Self>>> {
+        let backend = CrosstermBackend::new(stdout());
+        let Size { width, height } = backend.size()?;
+        Ok(Arc::new(RwLock::new(Self {
+            exited:  Arc::new(AtomicBool::new(false)),
+            buffer:  Buffer::empty(Rect { x: 0, y: 0, width, height }),
+            area:    [0, 0, width, height],
+            backend,
+        })))
+    }
+    /// Update the display buffer.
+    pub fn flip (&mut self, mut buffer: Buffer, size: ratatui::prelude::Rect) -> Buffer {
+        if self.buffer.area != size {
+            self.backend.clear_region(ClearType::All).unwrap();
+            self.buffer.resize(size);
+            self.buffer.reset();
+        }
+        let updates = self.buffer.diff(&buffer);
+        self.backend.draw(updates.into_iter()).expect("failed to render");
+        self.backend.flush().expect("failed to flush output buffer");
+        std::mem::swap(&mut self.buffer, &mut buffer);
+        buffer.reset();
+        buffer
+    }
+}