fix(compatibility): improve vttest (#1671)

* Improve 'vttest' scenarios:

1. Report terminal as VT220 with sixel rather than VT400 family with
   sixel. This fixes a hang when launching vttest as it is waiting for
   a response to DECRQSS.

2. Test 6.2: Support NewLine mode (CR --> CRLF).

3. Test 6.3: Fix DSR cursor position report to honor scrolling region.

4. Test 6.7: Parse and respond to DECREQTPARM (Request Terminal
   Parameters - CSI x).  This is a VT100 sequence that xterm used to
   respond to always, but more recently only responds to when
   explicitly set to VT100 level.

* cargo fmt

* Fix failing unit test snapshot

* fix clippy error

* VT100 UK character set

5 files changed, 85 insertions, 12 deletions

diff --git a/zellij-server/src/panes/grid.rs b/zellij-server/src/panes/grid.rs
index 7150fd7a..98ea652b 100644
--- a/zellij-server/src/panes/grid.rs
+++ b/zellij-server/src/panes/grid.rs
@@ -352,6 +352,7 @@ pub struct Grid {
     pub sixel_scrolling: bool,      // DECSDM
     pub insert_mode: bool,
     pub disable_linewrap: bool,
+    pub new_line_mode: bool, // Automatic newline LNM
     pub clear_viewport_before_rendering: bool,
     pub width: usize,
     pub height: usize,
@@ -478,6 +479,7 @@ impl Grid {
             sixel_scrolling: false,
             insert_mode: false,
             disable_linewrap: false,
+            new_line_mode: false,
             alternate_screen_state: None,
             clear_viewport_before_rendering: false,
             active_charset: Default::default(),
@@ -1515,6 +1517,7 @@ impl Grid {
         self.active_charset = Default::default();
         self.erasure_mode = false;
         self.disable_linewrap = false;
+        self.new_line_mode = false;
         self.cursor.change_shape(CursorShape::Initial);
         self.output_buffer.update_all_lines();
         self.changed_colors = None;
@@ -2350,8 +2353,18 @@ impl Perform for Grid {
                         _ => {},
                     };
                 }
-            } else if let Some(4) = params_iter.next().map(|param| param[0]) {
-                self.insert_mode = false;
+            } else {
+                for param in params_iter.map(|param| param[0]) {
+                    match param {
+                        4 => {
+                            self.insert_mode = false;
+                        },
+                        20 => {
+                            self.new_line_mode = false;
+                        },
+                        _ => {},
+                    }
+                }
             }
         } else if c == 'h' {
             let first_intermediate_is_questionmark = match intermediates.get(0) {
@@ -2434,8 +2447,18 @@ impl Perform for Grid {
                         _ => {},
                     }
                 }
-            } else if let Some(4) = params_iter.next().map(|param| param[0]) {
-                self.insert_mode = true;
+            } else {
+                for param in params_iter.map(|param| param[0]) {
+                    match param {
+                        4 => {
+                            self.insert_mode = true;
+                        },
+                        20 => {
+                            self.new_line_mode = true;
+                        },
+                        _ => {},
+                    }
+                }
             }
         } else if c == 'r' {
             if params.len() > 1 {
@@ -2602,8 +2625,8 @@ impl Perform for Grid {
             // https://vt100.net/docs/vt510-rm/DA1.html
             match intermediates.get(0) {
                 None | Some(0) => {
-                    // primary device attributes
-                    let terminal_capabilities = "\u{1b}[?64;4c";
+                    // primary device attributes - VT220 with sixel
+                    let terminal_capabilities = "\u{1b}[?62;4c";
                     self.pending_messages_to_pty
                         .push(terminal_capabilities.as_bytes().to_vec());
                 },
@@ -2627,13 +2650,41 @@ impl Perform for Grid {
                 },
                 6 => {
                     // CPR - cursor position report
-                    let position_report =
-                        format!("\x1b[{};{}R", self.cursor.y + 1, self.cursor.x + 1);
+
+                    // Note that this is relative to scrolling region.
+                    let offset = match self.scroll_region {
+                        Some((scroll_region_top, _scroll_region_bottom)) => scroll_region_top,
+                        _ => 0,
+                    };
+                    let position_report = format!(
+                        "\u{1b}[{};{}R",
+                        self.cursor.y + 1 - offset,
+                        self.cursor.x + 1
+                    );
                     self.pending_messages_to_pty
                         .push(position_report.as_bytes().to_vec());
                 },
                 _ => {},
             }
+        } else if c == 'x' {
+            // DECREQTPARM - Request Terminal Parameters
+            // https://vt100.net/docs/vt100-ug/chapter3.html#DECREQTPARM
+            //
+            // Respond with (same as xterm): Parity NONE, 8 bits,
+            // xmitspeed 38400, recvspeed 38400.  (CLoCk MULtiplier =
+            // 1, STP option flags = 0)
+            //
+            // (xterm used to respond to DECREQTPARM in all modes.
+            // Now it seems to only do so when explicitly in VT100 mode.)
+            let query = next_param_or(0);
+            match query {
+                0 | 1 => {
+                    let response = format!("\u{1b}[{};1;1;128;128;1;0x", query + 2);
+                    self.pending_messages_to_pty
+                        .push(response.as_bytes().to_vec());
+                },
+                _ => {},
+            }
         } else if c == 't' {
             match next_param_or(1) as usize {
                 14 => {
@@ -2678,6 +2729,19 @@ impl Perform for Grid {
 
     fn esc_dispatch(&mut self, intermediates: &[u8], _ignore: bool, byte: u8) {
         match (byte, intermediates.get(0)) {
+            (b'A', charset_index_symbol) => {
+                let charset_index: CharsetIndex = match charset_index_symbol {
+                    Some(b'(') => CharsetIndex::G0,
+                    Some(b')') => CharsetIndex::G1,
+                    Some(b'*') => CharsetIndex::G2,
+                    Some(b'+') => CharsetIndex::G3,
+                    _ => {
+                        // invalid, silently do nothing
+                        return;
+                    },
+                };
+                self.configure_charset(StandardCharset::UK, charset_index);
+            },
             (b'B', charset_index_symbol) => {
                 let charset_index: CharsetIndex = match charset_index_symbol {
                     Some(b'(') => CharsetIndex::G0,
diff --git a/zellij-server/src/panes/terminal_character.rs b/zellij-server/src/panes/terminal_character.rs
index e933866e..c6fa0adf 100644
--- a/zellij-server/src/panes/terminal_character.rs
+++ b/zellij-server/src/panes/terminal_character.rs
@@ -586,6 +586,7 @@ impl Default for CharsetIndex {
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum StandardCharset {
     Ascii,
+    UK,
     SpecialCharacterAndLineDrawing,
 }
 
@@ -602,6 +603,10 @@ impl StandardCharset {
     pub fn map(self, c: char) -> char {
         match self {
             StandardCharset::Ascii => c,
+            StandardCharset::UK => match c {
+                '#' => '£',
+                _ => c,
+            },
             StandardCharset::SpecialCharacterAndLineDrawing => match c {
                 '`' => '◆',
                 'a' => '▒',
diff --git a/zellij-server/src/panes/terminal_pane.rs b/zellij-server/src/panes/terminal_pane.rs
index b305a03a..156b1249 100644
--- a/zellij-server/src/panes/terminal_pane.rs
+++ b/zellij-server/src/panes/terminal_pane.rs
@@ -162,6 +162,12 @@ impl Pane for TerminalPane {
         // needs to be adjusted.
         // here we match against those cases - if need be, we adjust the input and if not
         // we send back the original input
+        if self.grid.new_line_mode {
+            if let &[13] = input_bytes.as_slice() {
+                // LNM - carriage return is followed by linefeed
+                return "\u{0d}\u{0a}".as_bytes().to_vec();
+            };
+        }
         if self.grid.cursor_key_mode {
             match input_bytes.as_slice() {
                 LEFT_ARROW => {
diff --git a/zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__terminal_reports.snap b/zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__terminal_reports.snap
index aef38672..7b555da7 100644
--- a/zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__terminal_reports.snap
+++ b/zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__terminal_reports.snap
@@ -1,6 +1,5 @@
 ---
 source: zellij-server/src/panes/./unit/grid_tests.rs
-assertion_line: 721
 expression: "format!(\"{:?}\", grid.pending_messages_to_pty)"
 ---
-[[27, 91, 63, 54, 52, 59, 52, 99], [27, 91, 56, 59, 53, 49, 59, 57, 55, 116], [27, 91, 63, 54, 99], [27, 91, 48, 110], [27, 91, 49, 59, 49, 82]]
+[[27, 91, 63, 54, 50, 59, 52, 99], [27, 91, 56, 59, 53, 49, 59, 57, 55, 116], [27, 91, 63, 54, 99], [27, 91, 48, 110], [27, 91, 49, 59, 49, 82]]
diff --git a/zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__vttest3_0.snap b/zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__vttest3_0.snap
index 5b11dd9b..3a374540 100644
--- a/zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__vttest3_0.snap
+++ b/zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__vttest3_0.snap
@@ -1,7 +1,6 @@
 ---
 source: zellij-server/src/panes/./unit/grid_tests.rs
 expression: "format!(\"{:?}\", grid)"
-
 ---
 00 (C):          Selected as G0 (with SI)              Selected as G1 (with SO)                                       
 01 (C):                                                                                                               
@@ -10,7 +9,7 @@ expression: "format!(\"{:?}\", grid)"
 04 (C):          @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_      @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_                               
 05 (C):          `abcdefghijklmnopqrstuvwxyz{|}~       `abcdefghijklmnopqrstuvwxyz{|}~                                
 06 (C): Character set A (British)                                                                                     
-07 (C):           !"#$%&'()*+,-./0123456789:;<=>?       !"#$%&'()*+,-./0123456789:;<=>?                               
+07 (C):           !"£$%&'()*+,-./0123456789:;<=>?       !"£$%&'()*+,-./0123456789:;<=>?                               
 08 (C):          @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_      @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_                               
 09 (C):          `abcdefghijklmnopqrstuvwxyz{|}~       `abcdefghijklmnopqrstuvwxyz{|}~                                
 10 (C): Character set 0 (DEC Special graphics and line drawing)