feat: Add ability to highlight source code

examples/highlight_source.rs

@@ -22,6 +22,7 @@ fn main() {}
                             AnnotationKind::Primary
                                 .span(72..85)
                                 .label("allocation not allowed in constants")
+                                .highlight_source(true),
                         ),
                 )
                 .element(

src/renderer/mod.rs

@@ -1260,6 +1260,15 @@ impl Renderer {
                         underline.style,
                     );
                 }
+                _ if annotation.highlight_source => {
+                    buffer.set_style_range(
+                        line_offset,
+                        (code_offset + annotation.start.display).saturating_sub(left),
+                        (code_offset + annotation.end.display).saturating_sub(left),
+                        underline.style,
+                        annotation.is_primary(),
+                    );
+                }
                 _ => {}
             }
         }
@@ -2471,6 +2480,9 @@ pub(crate) struct LineAnnotation<'a> {
     /// Is this a single line, multiline or multiline span minimized down to a
     /// smaller span.
     pub annotation_type: LineAnnotationType,
+
+    /// Whether the source code should be highlighted
+    pub highlight_source: bool,
 }
 
 impl LineAnnotation<'_> {

src/renderer/source_map.rs

@@ -149,7 +149,13 @@ impl<'a> SourceMap<'a> {
             .collect::<Vec<_>>();
         let mut multiline_annotations = vec![];
 
-        for Annotation { range, label, kind } in annotations {
+        for Annotation {
+            range,
+            label,
+            kind,
+            highlight_source,
+        } in annotations
+        {
             let (lo, mut hi) = self.span_to_locations(range.clone());
 
             // Watch out for "empty spans". If we get a span like 6..6, we
@@ -169,6 +175,7 @@ impl<'a> SourceMap<'a> {
                     kind,
                     label,
                     annotation_type: LineAnnotationType::Singleline,
+                    highlight_source,
                 };
                 self.add_annotation_to_file(&mut annotated_line_infos, lo.line, line_ann);
             } else {
@@ -179,6 +186,7 @@ impl<'a> SourceMap<'a> {
                     kind,
                     label,
                     overlaps_exactly: false,
+                    highlight_source,
                 });
             }
         }
@@ -502,6 +510,7 @@ pub(crate) struct MultilineAnnotation<'a> {
     pub kind: AnnotationKind,
     pub label: Option<&'a str>,
     pub overlaps_exactly: bool,
+    pub highlight_source: bool,
 }
 
 impl<'a> MultilineAnnotation<'a> {
@@ -526,6 +535,7 @@ impl<'a> MultilineAnnotation<'a> {
             kind: self.kind,
             label: None,
             annotation_type: LineAnnotationType::MultilineStart(self.depth),
+            highlight_source: self.highlight_source,
         }
     }
 
@@ -541,6 +551,7 @@ impl<'a> MultilineAnnotation<'a> {
             kind: self.kind,
             label: self.label,
             annotation_type: LineAnnotationType::MultilineEnd(self.depth),
+            highlight_source: self.highlight_source,
         }
     }
 
@@ -551,6 +562,7 @@ impl<'a> MultilineAnnotation<'a> {
             kind: self.kind,
             label: None,
             annotation_type: LineAnnotationType::MultilineLine(self.depth),
+            highlight_source: self.highlight_source,
         }
     }
 }

src/snippet.rs

@@ -273,13 +273,19 @@ pub struct Annotation<'a> {
     pub(crate) range: Range<usize>,
     pub(crate) label: Option<&'a str>,
     pub(crate) kind: AnnotationKind,
+    pub(crate) highlight_source: bool,
 }
 
 impl<'a> Annotation<'a> {
     pub fn label(mut self, label: &'a str) -> Self {
         self.label = Some(label);
         self
     }
+
+    pub fn highlight_source(mut self, highlight_source: bool) -> Self {
+        self.highlight_source = highlight_source;
+        self
+    }
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
@@ -296,6 +302,7 @@ impl AnnotationKind {
             range: span,
             label: None,
             kind: self,
+            highlight_source: false,
         }
     }