Textarea optimizations

CHANGELOG.md

@@ -15,6 +15,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ## Changed
 
 - Widget.release_mouse will now only release the mouse, if it was captured by self https://github.com/Textualize/textual/pull/5900
+- Some optimizations to TextArea, which may be noticeable during scrolling (note: may break snapshots with a TextArea) https://github.com/Textualize/textual/pull/5925
+- Selecting in the TextArea now hides the cursor until you release the mouse https://github.com/Textualize/textual/pull/5925
+- Read only TextAreas will no longer display a cursor https://github.com/Textualize/textual/pull/5925
 
 ## Added
 

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

@@ -9,12 +9,14 @@
 from typing import TYPE_CHECKING, ClassVar, Iterable, Optional, Sequence, Tuple
 
 from rich.console import RenderableType
+from rich.segment import Segment
 from rich.style import Style
 from rich.text import Text
 from typing_extensions import Literal
 
 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,
@@ -511,6 +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
@@ -610,6 +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.
 
@@ -633,6 +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:
@@ -1035,6 +1043,7 @@ def wrap_width(self) -> int:
 
     def _rewrap_and_refresh_virtual_size(self) -> None:
         self.wrapped_document.wrap(self.wrap_width, tab_width=self.indent_width)
+        self._line_cache.clear()
         self._refresh_size()
 
     @property
@@ -1105,20 +1114,67 @@ def get_line(self, line_index: int) -> Text:
             A `rich.Text` object containing the requested line.
         """
         line_string = self.document.get_line(line_index)
-        return Text(line_string, end="")
+        return Text(line_string, end="", no_wrap=True)
+
+    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
+            ),
+            (
+                selection.end
+                if (
+                    self._cursor_visible
+                    and self.cursor_blink
+                    and absolute_y == selection.end[0]
+                )
+                else None
+            ),
+            self.theme,
+            self._matching_bracket_location,
+            self.match_cursor_bracket,
+            self.soft_wrap,
+            self.show_line_numbers,
+            self.read_only,
+        )
+        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.
 
         Returns:
             A rendered line.
         """
         theme = self._theme
-        if theme:
-            theme.apply_css(self)
 
         wrapped_document = self.wrapped_document
         scroll_x, scroll_y = self.scroll_offset
@@ -1173,7 +1229,8 @@ def render_line(self, y: int) -> Strip:
             if selection_style:
                 if line_character_count == 0 and line_index != cursor_row:
                     # A simple highlight to show empty lines are included in the selection
-                    line = Text("▌", end="", style=Style(color=selection_style.bgcolor))
+                    line.plain = "▌"
+                    line.stylize(Style(color=selection_style.bgcolor))
                 else:
                     if line_index == selection_top_row == selection_bottom_row:
                         # Selection within a single line
@@ -1222,6 +1279,7 @@ def render_line(self, y: int) -> Strip:
                 self.has_focus
                 and not self.cursor_blink
                 or (self.cursor_blink and self._cursor_visible)
+                and not self.read_only
             )
             if draw_matched_brackets:
                 matching_bracket_style = theme.bracket_matching_style if theme else None
@@ -1263,13 +1321,11 @@ def render_line(self, y: int) -> Strip:
             gutter_content = (
                 str(line_index + self.line_number_start) if section_offset == 0 else ""
             )
-            gutter = Text(
-                f"{gutter_content:>{gutter_width_no_margin}}  ",
-                style=gutter_style or "",
-                end="",
-            )
+            gutter = [
+                Segment(f"{gutter_content:>{gutter_width_no_margin}}  ", gutter_style)
+            ]
         else:
-            gutter = Text("", end="")
+            gutter = []
 
         # TODO: Lets not apply the division each time through render_line.
         #  We should cache sections with the edit counts.
@@ -1304,17 +1360,10 @@ def render_line(self, y: int) -> Strip:
             else max(virtual_width, self.region.size.width)
         )
         target_width = base_width - self.gutter_width
-        console = self.app.console
-        gutter_segments = console.render(gutter)
-
-        text_segments = list(
-            console.render(line, console.options.update_width(target_width))
-        )
-
-        gutter_strip = Strip(gutter_segments, cell_length=gutter_width)
-        text_strip = Strip(text_segments)
 
         # Crop the line to show only the visible part (some may be scrolled out of view)
+        console = self.app.console
+        text_strip = Strip(line.render(console), cell_length=line.cell_len)
         if not self.soft_wrap:
             text_strip = text_strip.crop(scroll_x, scroll_x + virtual_width)
 
@@ -1325,7 +1374,7 @@ def render_line(self, y: int) -> Strip:
             line_style = theme.base_style if theme else None
 
         text_strip = text_strip.extend_cell_length(target_width, line_style)
-        strip = Strip.join([gutter_strip, text_strip]).simplify()
+        strip = Strip.join([Strip(gutter, cell_length=gutter_width), text_strip])
 
         return strip.apply_style(
             theme.base_style
@@ -1645,7 +1694,7 @@ async def _on_mouse_down(self, event: events.MouseDown) -> None:
         # Capture the mouse so that if the cursor moves outside the
         # TextArea widget while selecting, the widget still scrolls.
         self.capture_mouse()
-        self._pause_blink(visible=True)
+        self._pause_blink(visible=False)
         self.history.checkpoint()
 
     async def _on_mouse_move(self, event: events.MouseMove) -> None: