feat: Don't normailze title text

Author: Muscraft

examples/highlight_title.svg

@@ -45,6 +45,13 @@
 pub mod renderer;
 mod snippet;
 
+/// Normalize the string to avoid any unicode control characters.
+/// This is important for untrusted input, as it can contain
+/// invalid unicode sequences.
+pub fn normalize_untrusted_str(s: &str) -> String {
+    renderer::normalize_whitespace(s)
+}
+
 #[doc(inline)]
 pub use renderer::Renderer;
 pub use snippet::ColumnSeparator;

src/lib.rs

@@ -573,8 +573,7 @@ impl Renderer {
         } else {
             ElementStyle::NoStyle
         };
-        let text = &normalize_whitespace(title);
-        let lines = text.split('\n').collect::<Vec<_>>();
+        let lines = title.split('\n').collect::<Vec<_>>();
         if lines.len() > 1 {
             for (i, line) in lines.iter().enumerate() {
                 if i != 0 {
@@ -584,7 +583,7 @@ impl Renderer {
                 buffer.append(line_number, line, style);
             }
         } else {
-            buffer.append(line_number, text, style);
+            buffer.append(line_number, title, style);
         }
         line_number
     }
@@ -2590,7 +2589,7 @@ const OUTPUT_REPLACEMENTS: &[(char, &str)] = &[
     ('\u{2069}', "�"),
 ];
 
-fn normalize_whitespace(s: &str) -> String {
+pub(crate) fn normalize_whitespace(s: &str) -> String {
     // Scan the input string for a character in the ordered table above.
     // If it's present, replace it with its alternative string (it can be more than 1 char!).
     // Otherwise, retain the input char.

src/renderer/mod.rs

@@ -177,6 +177,10 @@ impl Level {
         }
     }
 
+    /// Text passed to this function is allowed to be pre-styled, as such all
+    /// text is considered "trusted input" and has no normalizations applied to
+    /// it. [`normalize_untrusted_str`](crate::normalize_untrusted_str) can be
+    /// used to normalize untrusted text before it is passed to this function.
     pub fn title(self, title: &str) -> Title<'_> {
         Title {
             level: self,