termwiz/term: introduce KeyboardEncoding enum, existence of win32-input-mode

This is a baby step that formalizes the different encoding schemes into
an enum, and hooks up the decset sequence for win32-input-mode.

It doesn't change any of the actual encoding at this time.

refs: #1509

term/src/terminalstate/keyboard.rs

@@ -1,8 +1,17 @@
 use crate::input::*;
 use crate::TerminalState;
-use termwiz::input::KeyCodeEncodeModes;
+use termwiz::input::{KeyCodeEncodeModes, KeyboardEncoding};
 
 impl TerminalState {
+    fn effective_keyboard_encoding(&self) -> KeyboardEncoding {
+        match self.keyboard_encoding {
+            KeyboardEncoding::Xterm if self.config.enable_csi_u_key_encoding() => {
+                KeyboardEncoding::CsiU
+            }
+            enc => enc,
+        }
+    }
+
     /// Processes a key_down event generated by the gui/render layer
     /// that is embedding the Terminal.  This method translates the
     /// keycode into a sequence of bytes to send to the slave end
@@ -11,7 +20,7 @@ impl TerminalState {
         let to_send = key.encode(
             mods,
             KeyCodeEncodeModes {
-                enable_csi_u_key_encoding: self.config.enable_csi_u_key_encoding(),
+                encoding: self.effective_keyboard_encoding(),
                 newline_mode: self.newline_mode,
                 application_cursor_keys: self.application_cursor_keys,
             },

term/src/terminalstate/mod.rs

@@ -17,6 +17,7 @@ use termwiz::escape::csi::{
 };
 use termwiz::escape::{OneBased, OperatingSystemCommand, CSI};
 use termwiz::image::ImageData;
+use termwiz::input::KeyboardEncoding;
 use termwiz::surface::{CursorShape, CursorVisibility, SequenceNo};
 use url::Url;
 
@@ -314,6 +315,7 @@ pub struct TerminalState {
     last_mouse_move: Option<MouseEvent>,
     cursor_visible: bool,
 
+    keyboard_encoding: KeyboardEncoding,
     /// Support for US, UK, and DEC Special Graphics
     g0_charset: CharSet,
     g1_charset: CharSet,
@@ -469,6 +471,7 @@ impl TerminalState {
             bracketed_paste: false,
             focus_tracking: false,
             mouse_encoding: MouseEncoding::X10,
+            keyboard_encoding: KeyboardEncoding::Xterm,
             sixel_scrolls_right: false,
             any_event_mouse: false,
             button_event_mouse: false,
@@ -1211,6 +1214,22 @@ impl TerminalState {
                 // We leave key repeat to the GUI layer prefs
             }
 
+            Mode::SetDecPrivateMode(DecPrivateMode::Code(DecPrivateModeCode::Win32InputMode)) => {
+                self.keyboard_encoding = KeyboardEncoding::Win32;
+            }
+
+            Mode::ResetDecPrivateMode(DecPrivateMode::Code(DecPrivateModeCode::Win32InputMode)) => {
+                self.keyboard_encoding = KeyboardEncoding::Xterm;
+            }
+
+            Mode::QueryDecPrivateMode(DecPrivateMode::Code(DecPrivateModeCode::Win32InputMode)) => {
+                self.decqrm_response(
+                    mode,
+                    true,
+                    self.keyboard_encoding == KeyboardEncoding::Win32,
+                );
+            }
+
             Mode::SetDecPrivateMode(DecPrivateMode::Code(
                 DecPrivateModeCode::ReverseWraparound,
             )) => {

term/src/terminalstate/performer.rs

@@ -17,6 +17,7 @@ use termwiz::escape::osc::{
 use termwiz::escape::{
     Action, ControlCode, DeviceControlMode, Esc, EscCode, OperatingSystemCommand, CSI,
 };
+use termwiz::input::KeyboardEncoding;
 use url::Url;
 
 /// A helper struct for implementing `vtparse::VTActor` while compartmentalizing
@@ -516,6 +517,7 @@ impl<'a> Performer<'a> {
                 self.bracketed_paste = false;
                 self.focus_tracking = false;
                 self.mouse_encoding = MouseEncoding::X10;
+                self.keyboard_encoding = KeyboardEncoding::Xterm;
                 self.sixel_scrolls_right = false;
                 self.any_event_mouse = false;
                 self.button_event_mouse = false;

termwiz/src/escape/csi.rs

@@ -757,6 +757,10 @@ pub enum DecPrivateModeCode {
 
     /// xterm: adjust cursor positioning after emitting sixel
     SixelScrollsRight = 8452,
+
+    /// Windows Terminal: win32-input-mode
+    /// <https://github.com/microsoft/terminal/blob/main/doc/specs/%234999%20-%20Improved%20keyboard%20handling%20in%20Conpty.md>
+    Win32InputMode = 9001,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]

termwiz/src/input.rs

@@ -15,11 +15,20 @@ use std::fmt::Write;
 pub const CSI: &str = "\x1b[";
 pub const SS3: &str = "\x1bO";
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum KeyboardEncoding {
+    Xterm,
+    /// <http://www.leonerd.org.uk/hacks/fixterms/>
+    CsiU,
+    /// <https://github.com/microsoft/terminal/blob/main/doc/specs/%234999%20-%20Improved%20keyboard%20handling%20in%20Conpty.md>
+    Win32,
+}
+
 /// Specifies terminal modes/configuration that can influence how a KeyCode
 /// is encoded when being sent to and application via the pty.
 #[derive(Debug, Clone, Copy)]
 pub struct KeyCodeEncodeModes {
-    pub enable_csi_u_key_encoding: bool,
+    pub encoding: KeyboardEncoding,
     pub application_cursor_keys: bool,
     pub newline_mode: bool,
 }
@@ -275,12 +284,12 @@ impl KeyCode {
             Char(c)
                 if is_ambiguous_ascii_ctrl(c)
                     && mods.contains(Modifiers::CTRL)
-                    && modes.enable_csi_u_key_encoding =>
+                    && modes.encoding == KeyboardEncoding::CsiU =>
             {
-                csi_u_encode(&mut buf, c, mods, modes.enable_csi_u_key_encoding)?;
+                csi_u_encode(&mut buf, c, mods, modes.encoding)?;
             }
             Char(c) if c.is_ascii_uppercase() && mods.contains(Modifiers::CTRL) => {
-                csi_u_encode(&mut buf, c, mods, modes.enable_csi_u_key_encoding)?;
+                csi_u_encode(&mut buf, c, mods, modes.encoding)?;
             }
 
             Char(c) if mods.contains(Modifiers::CTRL) && ctrl_mapping(c).is_some() => {
@@ -314,7 +323,7 @@ impl KeyCode {
                     _ => unreachable!(),
                 };
                 if mods.contains(Modifiers::SHIFT) || mods.contains(Modifiers::CTRL) {
-                    csi_u_encode(&mut buf, c, mods, modes.enable_csi_u_key_encoding)?;
+                    csi_u_encode(&mut buf, c, mods, modes.encoding)?;
                 } else {
                     if mods.contains(Modifiers::ALT) {
                         buf.push(0x1b as char);
@@ -346,7 +355,7 @@ impl KeyCode {
                 if mods.is_empty() {
                     buf.push(c);
                 } else {
-                    csi_u_encode(&mut buf, c, mods, modes.enable_csi_u_key_encoding)?;
+                    csi_u_encode(&mut buf, c, mods, modes.encoding)?;
                 }
             }
 
@@ -555,9 +564,9 @@ fn csi_u_encode(
     buf: &mut String,
     c: char,
     mods: Modifiers,
-    enable_csi_u_key_encoding: bool,
+    encoding: KeyboardEncoding,
 ) -> Result<()> {
-    if enable_csi_u_key_encoding {
+    if encoding == KeyboardEncoding::CsiU {
         write!(buf, "\x1b[{};{}u", c as u32, 1 + encode_modifiers(mods))?;
     } else {
         let c = if mods.contains(Modifiers::CTRL) && ctrl_mapping(c).is_some() {
@@ -1522,7 +1531,7 @@ mod test {
     #[test]
     fn encode_issue_892() {
         let mode = KeyCodeEncodeModes {
-            enable_csi_u_key_encoding: false,
+            encoding: KeyboardEncoding::Xterm,
             newline_mode: false,
             application_cursor_keys: false,
         };