line cache

Author: willmcgugan

src/textual/document/_document.py

@@ -466,3 +466,8 @@ def is_empty(self) -> bool:
         """Return True if the selection has 0 width, i.e. it's just a cursor."""
         start, end = self
         return start == end
+
+    def contains_line(self, y: int) -> bool:
+        """Check if the given line is within the selection."""
+        top, bottom = sorted((self.start[0], self.end[0]))
+        return y >= top and y <= bottom

src/textual/widgets/_text_area.py

@@ -16,6 +16,7 @@
 
 from textual._text_area_theme import TextAreaTheme
 from textual._tree_sitter import TREE_SITTER, get_language
+from textual.cache import LRUCache
 from textual.color import Color
 from textual.document._document import (
     Document,
@@ -512,6 +513,8 @@ def __init__(
         self.set_reactive(TextArea.line_number_start, line_number_start)
         self.set_reactive(TextArea.highlight_cursor_line, highlight_cursor_line)
 
+        self._line_cache: LRUCache[tuple, Strip] = LRUCache(1024)
+
         self._set_document(text, language)
 
         self.language = language
@@ -611,6 +614,9 @@ def _get_builtin_highlight_query(language_name: str) -> str:
 
         return highlight_query
 
+    def notify_style_update(self) -> None:
+        self._line_cache.clear()
+
     def check_consume_key(self, key: str, character: str | None = None) -> bool:
         """Check if the widget may consume the given key.
 
@@ -634,6 +640,7 @@ def check_consume_key(self, key: str, character: str | None = None) -> bool:
 
     def _build_highlight_map(self) -> None:
         """Query the tree for ranges to highlights, and update the internal highlights mapping."""
+        self._line_cache.clear()
         highlights = self._highlights
         highlights.clear()
         if not self._highlight_query:
@@ -838,6 +845,8 @@ def _set_theme(self, theme: str) -> None:
                 if background:
                     self.styles.background = Color.from_rich_color(background)
 
+        theme_object.apply_css(self)
+
     @property
     def available_themes(self) -> set[str]:
         """A list of the names of the themes available to the `TextArea`.
@@ -1108,15 +1117,42 @@ def get_line(self, line_index: int) -> Text:
         line_string = self.document.get_line(line_index)
         return Text(line_string, end="")
 
-    def render_lines(self, crop: Region) -> list[Strip]:
-        theme = self._theme
-        if theme:
-            theme.apply_css(self)
-        return super().render_lines(crop)
-
     def render_line(self, y: int) -> Strip:
         """Render a single line of the TextArea. Called by Textual.
 
+        Args:
+            y: Y Coordinate of line relative to the widget region.
+
+        Returns:
+            A rendered line.
+        """
+        scroll_x, scroll_y = self.scroll_offset
+        absolute_y = scroll_y + y
+        selection = self.selection
+        cache_key = (
+            self.size,
+            scroll_x,
+            absolute_y,
+            (
+                selection
+                if selection.contains_line(absolute_y)
+                else selection.end[0] == absolute_y
+            ),
+            self._cursor_visible,
+            self.cursor_blink,
+            self.theme,
+            self._matching_bracket_location,
+            self.match_cursor_bracket,
+        )
+        if (cached_line := self._line_cache.get(cache_key)) is not None:
+            return cached_line
+        line = self._render_line(y)
+        self._line_cache[cache_key] = line
+        return line
+
+    def _render_line(self, y: int) -> Strip:
+        """Render a single line of the TextArea. Called by Textual.
+
         Args:
             y: Y Coordinate of line relative to the widget region.
 
@@ -1310,7 +1346,10 @@ def render_line(self, y: int) -> Strip:
 
         # Crop the line to show only the visible part (some may be scrolled out of view)
         console = self.app.console
-        text_strip = Strip(console.render(line), cell_length=line.cell_len)
+        text_strip = Strip(
+            console.render(line, options=console.options.update_width(line.cell_len)),
+            cell_length=line.cell_len,
+        )
         if not self.soft_wrap:
             text_strip = text_strip.crop(scroll_x, scroll_x + virtual_width)