optimize highlight rendering

src/document.rs

@@ -157,7 +157,7 @@ impl Document {
 
         #[allow(clippy::indexing_slicing)]
         let current_row = &mut self.rows[at.y];
-        let new_row = self.rows[at.y].split(at.x);
+        let mut new_row = current_row.split(at.x);
 
         current_row.highlight();
         new_row.highlight();

src/highlighting.rs

@@ -1,5 +1,6 @@
 use termion::color;
 
+#[derive(PartialEq)]
 pub enum Type {
     None,
     Number,

src/row.rs

@@ -27,31 +27,41 @@ impl Row {
         let start = cmp::min(start, end);
 
         let mut result = String::new();
+        let mut current_highlighting = &highlighting::Type::None;
 
         #[allow(clippy::integer_arithmetic)]
-        for grapheme in self.string[..]
+        for (index, grapheme) in self.string[..]
             .graphemes(true)
+            .enumerate()
             .skip(start)
             .take(end - start)
         {
             if let Some(c) = grapheme.chars().next() {
+                let highlighting_type = self
+                    .highlighting
+                    .get(index)
+                    .unwrap_or(&highlighting::Type::None);
+
+                if highlighting_type != current_highlighting {
+                    current_highlighting = highlighting_type;
+
+                    let start_highlight =
+                        format!("{}", termion::color::Fg(highlighting_type.to_color()));
+
+                    result.push_str(&start_highlight[..]);
+                }
+
                 if c == '\t' {
                     result.push_str("    ");
-                } else if c.is_ascii_digit() {
-                    result.push_str(
-                        &format!(
-                            "{}{}{}",
-                            color::Fg(color::Rgb(220, 163, 163)),
-                            c,
-                            color::Fg(color::Reset)
-                        )[..],
-                    );
                 } else {
                     result.push(c);
                 }
             }
         }
 
+        let end_highlight = format!("{}", termion::color::Fg(color::Reset));
+        result.push_str(&end_highlight[..]);
+
         result
     }