Implementation of the XTSMGRAPHICS sequence.

4 files changed, 38 insertions, 2 deletions

diff --git a/alacritty_terminal/src/ansi.rs b/alacritty_terminal/src/ansi.rs
index 40515837..27b9231e 100644
--- a/alacritty_terminal/src/ansi.rs
+++ b/alacritty_terminal/src/ansi.rs
@@ -471,6 +471,9 @@ pub trait Handler {
     /// Report text area size in characters.
     fn text_area_size_chars<W: io::Write>(&mut self, _: &mut W) {}
 
+    /// Report a graphics attribute.
+    fn graphics_attribute<W: io::Write>(&mut self, _: &mut W, _: u16, _: u16) {}
+
     /// Create a parser for Sixel data.
     fn start_sixel_graphic(&mut self, _params: &Params) -> Option<Box<sixel::Parser>> {
         None
@@ -1282,6 +1285,7 @@ where
                 handler.set_scrolling_region(top, bottom);
             },
             ('S', []) => handler.scroll_up(next_param_or(1) as usize),
+            ('S', [b'?']) => handler.graphics_attribute(writer, next_param_or(0), next_param_or(0)),
             ('s', []) => handler.save_cursor_position(),
             ('T', []) => handler.scroll_down(next_param_or(1) as usize),
             ('t', []) => match next_param_or(1) as usize {
diff --git a/alacritty_terminal/src/graphics/sixel.rs b/alacritty_terminal/src/graphics/sixel.rs
index 476089cc..221fe7cd 100644
--- a/alacritty_terminal/src/graphics/sixel.rs
+++ b/alacritty_terminal/src/graphics/sixel.rs
@@ -33,7 +33,7 @@ use vte::Params;
 struct ColorRegister(u16);
 
 /// Number of color registers.
-const MAX_COLOR_REGISTERS: usize = 1024;
+pub const MAX_COLOR_REGISTERS: usize = 1024;
 
 /// Color register for transparent pixels.
 const REG_TRANSPARENT: ColorRegister = ColorRegister(u16::MAX);
diff --git a/alacritty_terminal/src/term/mod.rs b/alacritty_terminal/src/term/mod.rs
index ed14fa2f..3568f79c 100644
--- a/alacritty_terminal/src/term/mod.rs
+++ b/alacritty_terminal/src/term/mod.rs
@@ -983,7 +983,7 @@ impl<T: EventListener> Handler for Term<T> {
         match intermediate {
             None => {
                 trace!("Reporting primary device attributes");
-                let _ = writer.write_all(b"\x1b[?4;6c");
+                let _ = writer.write_all(b"\x1b[?6c");
             },
             Some('>') => {
                 trace!("Reporting secondary device attributes");
@@ -1718,6 +1718,37 @@ impl<T: EventListener> Handler for Term<T> {
         let _ = write!(writer, "\x1b[8;{};{}t", self.screen_lines(), self.columns());
     }
 
+    #[inline]
+    fn graphics_attribute<W: io::Write>(&mut self, writer: &mut W, pi: u16, pa: u16) {
+        // From Xterm documentation:
+        //
+        //   Pi = 1  -> item is number of color registers.
+        //   Pi = 2  -> item is Sixel graphics geometry (in pixels).
+        //
+        //   Pa = 1  -> read attribute.
+        //   Pa = 4  -> read the maximum allowed value.
+        //
+        // Any other request reports an error.
+
+        let (ps, pv) = if pa == 1 || pa == 4 {
+            match pi {
+                1 => (0, &[sixel::MAX_COLOR_REGISTERS][..]),
+                2 => (0, &[MAX_GRAPHIC_DIMENSIONS.0, MAX_GRAPHIC_DIMENSIONS.1][..]),
+                _ => (1, &[][..]), // Report error in Pi
+            }
+        } else {
+            (2, &[][..]) // Report error in Pa
+        };
+
+        let _ = write!(writer, "\x1b[?{};{}", pi, ps);
+
+        for item in pv {
+            let _ = write!(writer, ";{}", item);
+        }
+
+        let _ = write!(writer, "S");
+    }
+
     fn start_sixel_graphic(&mut self, params: &Params) -> Option<Box<sixel::Parser>> {
         let palette = self.graphics.sixel_shared_palette.take();
         Some(Box::new(sixel::Parser::new(params, palette)))
diff --git a/docs/escape_support.md b/docs/escape_support.md
index 5008d6a6..bc951753 100644
--- a/docs/escape_support.md
+++ b/docs/escape_support.md
@@ -71,6 +71,7 @@ brevity.
 | `CSI SP q` | IMPLEMENTED |                                                   |
 | `CSI r`    | IMPLEMENTED |                                                   |
 | `CSI S`    | IMPLEMENTED |                                                   |
+| `CSI ? S`  | PARTIAL     | Only for reading attributes.                      |
 | `CSI s`    | IMPLEMENTED |                                                   |
 | `CSI T`    | IMPLEMENTED |                                                   |
 | `CSI t`    | PARTIAL     | Only parameters `22` and `23` are supported       |