Cleaner scroll handling

pulse-ui/src/render.rs

@@ -15,58 +15,75 @@ pub struct RenderScope {
     draw_instructions: Vec<Instr>,
 }
 
+struct RenderTextResult {
+    text: String,
+    line_len: u16,
+    lines_len: u16,
+}
+
+impl RenderTextResult {
+    fn insert_newline(&mut self, height: u16) -> bool {
+        if self.lines_len >= height {
+            return true;
+        }
+
+        self.text.push('\n');
+        self.line_len = 0;
+        self.lines_len += 1;
+
+        false
+    }
+
+    fn insert(&mut self, c: char) {
+        self.text.push(c);
+        self.line_len += 1;
+    }
+}
+
 impl RenderScope {
     pub fn draw_text<P: Into<Point>, T: Display>(&mut self, at: P, text: T) -> u16 {
         let point: Point = at.into();
 
-        let lines = text
-            .to_string()
-            .lines()
-            .map(|line| {
-                let mut chars = line.chars().peekable();
-                let mut new_line = String::new();
-                let mut len = 0;
+        let text = text.to_string();
+
+        let mut chars = text.chars().peekable();
+
+        let mut result = RenderTextResult {
+            text: String::new(),
+            line_len: 0,
+            lines_len: 1,
+        };
+
+        while let Some(c) = chars.next() {
+            if c == '\x1b' && chars.peek() == Some(&'[') {
+                result.text.push(c);
 
                 while let Some(c) = chars.next() {
-                    if c == '\x1b' && chars.peek() == Some(&'[') {
-                        new_line.push(c);
+                    result.text.push(c);
 
-                        while let Some(c) = chars.next() {
-                            new_line.push(c);
-
-                            if c.is_ascii_alphabetic() {
-                                break;
-                            }
-                        }
-
-                        continue;
-                    }
-
-                    new_line.push(c);
-                    len += 1;
-
-                    if len >= self.rect.width as usize {
-                        new_line.push('\n');
-                        len = 0;
+                    if c.is_ascii_alphabetic() {
+                        break;
                     }
                 }
+            } else if c == '\n' {
+                if result.insert_newline(self.rect.height) {
+                    break;
+                }
+            } else {
+                result.insert(c);
 
-                new_line
-            })
-            .collect::<Vec<_>>()
-            .join("\n");
-
-        let lines = lines
-            .lines()
-            .take((self.rect.height - point.y) as usize)
-            .collect::<Vec<_>>();
-
-        let lines_len = lines.len();
+                if result.line_len >= self.rect.width {
+                    if result.insert_newline(self.rect.height) {
+                        break;
+                    }
+                }
+            }
+        }
 
         self.draw_instructions
-            .push(Instr::DrawText(point, lines.join("\n")));
+            .push(Instr::DrawText(point, result.text));
 
-        lines_len as u16
+        result.lines_len
     }
 }