Add support for hyperlink escape sequence

This commit adds support for hyperlink escape sequence
`OSC 8 ; params ; URI ST`. The configuration option responsible for
those is `hints.enabled.hyperlinks`.

Fixes #922.

4 files changed, 121 insertions, 6 deletions

diff --git a/alacritty_terminal/src/ansi.rs b/alacritty_terminal/src/ansi.rs
index 393f6a8c..e30ed0f5 100644
--- a/alacritty_terminal/src/ansi.rs
+++ b/alacritty_terminal/src/ansi.rs
@@ -12,6 +12,7 @@ use vte::{Params, ParamsIter};
 use alacritty_config_derive::ConfigDeserialize;
 
 use crate::index::{Column, Line};
+use crate::term::cell::Hyperlink;
 use crate::term::color::Rgb;
 
 /// Maximum time before a synchronized update is aborted.
@@ -457,6 +458,9 @@ pub trait Handler {
 
     /// Report text area size in characters.
     fn text_area_size_chars(&mut self) {}
+
+    /// Set hyperlink.
+    fn set_hyperlink(&mut self, _: Option<Hyperlink>) {}
 }
 
 /// Terminal cursor configuration.
@@ -1007,6 +1011,27 @@ where
                 }
             },
 
+            // Hyperlink.
+            b"8" if params.len() > 2 => {
+                let link_params = params[1];
+                let uri = str::from_utf8(params[2]).unwrap_or_default();
+
+                // The OSC 8 escape sequence must be stopped when getting an empty `uri`.
+                if uri.is_empty() {
+                    self.handler.set_hyperlink(None);
+                    return;
+                }
+
+                // Link parameters are in format of `key1=value1:key2=value2`. Currently only key
+                // `id` is defined.
+                let id = link_params
+                    .split(|&b| b == b':')
+                    .find_map(|kv| kv.strip_prefix(b"id="))
+                    .and_then(|kv| str::from_utf8(kv).ok());
+
+                self.handler.set_hyperlink(Some(Hyperlink::new(id, uri)));
+            },
+
             // Get/set Foreground, Background, Cursor colors.
             b"10" | b"11" | b"12" => {
                 if params.len() >= 2 {
diff --git a/alacritty_terminal/src/grid/row.rs b/alacritty_terminal/src/grid/row.rs
index f6bcb022..900d2a76 100644
--- a/alacritty_terminal/src/grid/row.rs
+++ b/alacritty_terminal/src/grid/row.rs
@@ -171,6 +171,16 @@ impl<T> Row<T> {
     }
 }
 
+impl<'a, T> IntoIterator for &'a Row<T> {
+    type IntoIter = slice::Iter<'a, T>;
+    type Item = &'a T;
+
+    #[inline]
+    fn into_iter(self) -> slice::Iter<'a, T> {
+        self.inner.iter()
+    }
+}
+
 impl<'a, T> IntoIterator for &'a mut Row<T> {
     type IntoIter = slice::IterMut<'a, T>;
     type Item = &'a mut T;
diff --git a/alacritty_terminal/src/term/cell.rs b/alacritty_terminal/src/term/cell.rs
index 716bcf9b..d3f45e9a 100644
--- a/alacritty_terminal/src/term/cell.rs
+++ b/alacritty_terminal/src/term/cell.rs
@@ -1,3 +1,4 @@
+use std::sync::atomic::{AtomicU32, Ordering};
 use std::sync::Arc;
 
 use bitflags::bitflags;
@@ -33,6 +34,53 @@ bitflags! {
     }
 }
 
+/// Counter for hyperlinks without explicit ID.
+static HYPERLINK_ID_SUFFIX: AtomicU32 = AtomicU32::new(0);
+
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Hyperlink {
+    inner: Arc<HyperlinkInner>,
+}
+
+impl Hyperlink {
+    pub fn new<T: ToString>(id: Option<T>, uri: T) -> Self {
+        let inner = Arc::new(HyperlinkInner::new(id, uri));
+        Self { inner }
+    }
+
+    pub fn id(&self) -> &str {
+        &self.inner.id
+    }
+
+    pub fn uri(&self) -> &str {
+        &self.inner.uri
+    }
+}
+
+#[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Hash)]
+struct HyperlinkInner {
+    /// Identifier for the given hyperlink.
+    id: String,
+
+    /// Resource identifier of the hyperlink.
+    uri: String,
+}
+
+impl HyperlinkInner {
+    pub fn new<T: ToString>(id: Option<T>, uri: T) -> Self {
+        let id = match id {
+            Some(id) => id.to_string(),
+            None => {
+                let mut id = HYPERLINK_ID_SUFFIX.fetch_add(1, Ordering::Relaxed).to_string();
+                id.push_str("_alacritty");
+                id
+            },
+        };
+
+        Self { id, uri: uri.to_string() }
+    }
+}
+
 /// Trait for determining if a reset should be performed.
 pub trait ResetDiscriminant<T> {
     /// Value based on which equality for the reset will be determined.
@@ -61,6 +109,8 @@ pub struct CellExtra {
     zerowidth: Vec<char>,
 
     underline_color: Option<Color>,
+
+    hyperlink: Option<Hyperlink>,
 }
 
 /// Content and attributes of a single cell in the terminal grid.
@@ -113,14 +163,17 @@ impl Cell {
     /// Set underline color on the cell.
     pub fn set_underline_color(&mut self, color: Option<Color>) {
         // If we reset color and we don't have zerowidth we should drop extra storage.
-        if color.is_none() && self.extra.as_ref().map_or(true, |extra| !extra.zerowidth.is_empty())
+        if color.is_none()
+            && self
+                .extra
+                .as_ref()
+                .map_or(true, |extra| !extra.zerowidth.is_empty() || extra.hyperlink.is_some())
         {
             self.extra = None;
-            return;
+        } else {
+            let extra = self.extra.get_or_insert(Default::default());
+            Arc::make_mut(extra).underline_color = color;
         }
-
-        let extra = self.extra.get_or_insert(Default::default());
-        Arc::make_mut(extra).underline_color = color;
     }
 
     /// Underline color stored in this cell.
@@ -128,6 +181,27 @@ impl Cell {
     pub fn underline_color(&self) -> Option<Color> {
         self.extra.as_ref()?.underline_color
     }
+
+    /// Set hyperlink.
+    pub fn set_hyperlink(&mut self, hyperlink: Option<Hyperlink>) {
+        let should_drop = hyperlink.is_none()
+            && self.extra.as_ref().map_or(true, |extra| {
+                !extra.zerowidth.is_empty() || extra.underline_color.is_some()
+            });
+
+        if should_drop {
+            self.extra = None;
+        } else {
+            let extra = self.extra.get_or_insert(Default::default());
+            Arc::make_mut(extra).hyperlink = hyperlink;
+        }
+    }
+
+    /// Hyperlink stored in this cell.
+    #[inline]
+    pub fn hyperlink(&self) -> Option<Hyperlink> {
+        self.extra.as_ref()?.hyperlink.clone()
+    }
 }
 
 impl GridCell for Cell {
diff --git a/alacritty_terminal/src/term/mod.rs b/alacritty_terminal/src/term/mod.rs
index d600cc78..1f3269c2 100644
--- a/alacritty_terminal/src/term/mod.rs
+++ b/alacritty_terminal/src/term/mod.rs
@@ -16,7 +16,7 @@ use crate::event::{Event, EventListener};
 use crate::grid::{Dimensions, Grid, GridIterator, Scroll};
 use crate::index::{self, Boundary, Column, Direction, Line, Point, Side};
 use crate::selection::{Selection, SelectionRange, SelectionType};
-use crate::term::cell::{Cell, Flags, LineLength};
+use crate::term::cell::{Cell, Flags, Hyperlink, LineLength};
 use crate::term::color::{Colors, Rgb};
 use crate::vi_mode::{ViModeCursor, ViMotion};
 
@@ -1679,6 +1679,12 @@ impl<T: EventListener> Handler for Term<T> {
         }
     }
 
+    #[inline]
+    fn set_hyperlink(&mut self, hyperlink: Option<Hyperlink>) {
+        trace!("Setting hyperlink: {:?}", hyperlink);
+        self.grid.cursor.template.set_hyperlink(hyperlink);
+    }
+
     /// Set a terminal attribute.
     #[inline]
     fn terminal_attribute(&mut self, attr: Attr) {