Poll for responses to feature queries

Some terminals don't respond to queries (even primary device attributes
request) at all. In that case we can wait for a while but should
eventually give up and use default capabilities.

Author: the-mikedavis

helix-tui/src/backend/termina.rs

@@ -116,7 +116,7 @@ impl TerminaBackend {
         terminal: &mut PlatformTerminal,
         config: &Config,
     ) -> io::Result<(Capabilities, String)> {
-        use std::time::Instant;
+        use std::time::{Duration, Instant};
 
         // Colibri "midnight"
         const TEST_COLOR: RgbColor = RgbColor::new(59, 34, 76);
@@ -151,36 +151,47 @@ impl TerminaBackend {
         )?;
         terminal.flush()?;
 
-        loop {
-            match terminal.read(Event::is_escape)? {
-                Event::Csi(Csi::Keyboard(csi::Keyboard::ReportFlags(_))) => {
-                    capabilities.kitty_keyboard = KittyKeyboardSupport::Some;
-                }
-                Event::Csi(Csi::Mode(csi::Mode::ReportDecPrivateMode {
-                    mode: csi::DecPrivateMode::Code(csi::DecPrivateModeCode::SynchronizedOutput),
-                    setting: csi::DecModeSetting::Set | csi::DecModeSetting::Reset,
-                })) => {
-                    capabilities.synchronized_output = true;
-                }
-                Event::Dcs(dcs::Dcs::Response {
-                    value: dcs::DcsResponse::GraphicRendition(sgrs),
-                    ..
-                }) => {
-                    capabilities.true_color =
-                        sgrs.contains(&csi::Sgr::Background(TEST_COLOR.into()));
-                    capabilities.extended_underlines =
-                        sgrs.contains(&csi::Sgr::UnderlineColor(TEST_COLOR.into()));
+        // TODO: tune this poll constant?
+        let device_attributes = |event: &Event| {
+            matches!(
+                event,
+                Event::Csi(Csi::Device(csi::Device::DeviceAttributes(_)))
+            )
+        };
+        if terminal.poll(device_attributes, Some(Duration::from_millis(20)))? {
+            loop {
+                match terminal.read(Event::is_escape)? {
+                    Event::Csi(Csi::Keyboard(csi::Keyboard::ReportFlags(_))) => {
+                        capabilities.kitty_keyboard = KittyKeyboardSupport::Some;
+                    }
+                    Event::Csi(Csi::Mode(csi::Mode::ReportDecPrivateMode {
+                        mode: csi::DecPrivateMode::Code(csi::DecPrivateModeCode::SynchronizedOutput),
+                        setting: csi::DecModeSetting::Set | csi::DecModeSetting::Reset,
+                    })) => {
+                        capabilities.synchronized_output = true;
+                    }
+                    Event::Dcs(dcs::Dcs::Response {
+                        value: dcs::DcsResponse::GraphicRendition(sgrs),
+                        ..
+                    }) => {
+                        capabilities.true_color =
+                            sgrs.contains(&csi::Sgr::Background(TEST_COLOR.into()));
+                        capabilities.extended_underlines =
+                            sgrs.contains(&csi::Sgr::UnderlineColor(TEST_COLOR.into()));
+                    }
+                    Event::Csi(Csi::Device(csi::Device::DeviceAttributes(_))) => break,
+                    _ => (),
                 }
-                Event::Csi(Csi::Device(csi::Device::DeviceAttributes(_))) => break,
-                _ => (),
             }
-        }
 
-        let end = Instant::now();
-        log::debug!(
-            "Detected terminal capabilities in {:?}: {capabilities:?}",
-            end.duration_since(start)
-        );
+            let end = Instant::now();
+            log::debug!(
+                "Detected terminal capabilities in {:?}: {capabilities:?}",
+                end.duration_since(start)
+            );
+        } else {
+            log::debug!("Failed to detect terminal capabilities within 20ms. Using default capabilities only");
+        }
 
         capabilities.extended_underlines |= config.force_enable_extended_underlines;