feat(whitespace): add whitespace rendering and custom char rendering

src/buffer/options.rs

@@ -1,13 +1,35 @@
+use std::collections::HashMap;
+
 pub struct BufferOptions {
     pub show_info_column: bool,
     pub show_border: bool,
+    pub chars: HashMap<char, char>,
 }
 
 impl Default for BufferOptions {
     fn default() -> Self {
-        Self {
+        let mut options = Self {
             show_info_column: true,
             show_border: false,
+            chars: HashMap::new(),
+        };
+        options.chars.insert(' ', '•');
+        options
+    }
+}
+
+impl BufferOptions {
+    pub fn replace_chars(&self, text: &str) -> String {
+        let mut result = String::new();
+
+        for c in text.chars() {
+            if let Some(m) = self.chars.get(&c) {
+                result.push(m.clone());
+            } else {
+                result.push(c);
+            }
         }
+
+        result
     }
 }

src/screen/print_buffer.rs

@@ -112,7 +112,7 @@ impl Screen {
                     self.print_text(
                         buffer.area.y + y,
                         buffer.text_area.x,
-                        &text,
+                        &buffer.options.replace_chars(&text),
                         Style::new(T.text_fg, T.text_bg),
                     );
                 }