fix infinite loop in cropping

CHANGELOG.md

@@ -5,11 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
-## Unreleased
+## [0.84.0] - 2024-10-22
 
 ### Fixed
 
 - Fixed `RadioSet` not being scrollable https://github.com/Textualize/textual/issues/5100
+- Fixed infinite loop in TextArea https://github.com/Textualize/textual/pull/5154
 
 ### Added
 
@@ -2453,6 +2454,7 @@ https://textual.textualize.io/blog/2022/11/08/version-040/#version-040
 - New handler system for messages that doesn't require inheritance
 - Improved traceback handling
 
+[0.84.0]: https://github.com/Textualize/textual/compare/v0.83.0...v0.84.0
 [0.83.0]: https://github.com/Textualize/textual/compare/v0.82.0...v0.83.0
 [0.82.0]: https://github.com/Textualize/textual/compare/v0.81.0...v0.82.0
 [0.81.0]: https://github.com/Textualize/textual/compare/v0.80.1...v0.81.0

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "textual"
-version = "0.83.0"
+version = "0.84.0"
 homepage = "https://github.com/Textualize/textual"
 repository = "https://github.com/Textualize/textual"
 documentation = "https://textual.textualize.io/"

src/textual/strip.py

@@ -372,10 +372,13 @@ def crop(self, start: int, end: int | None = None) -> Strip:
         Returns:
             A new Strip.
         """
+
         start = max(0, start)
         end = self.cell_length if end is None else min(self.cell_length, end)
         if start == 0 and end == self.cell_length:
             return self
+        if end <= start:
+            return Strip([], 0)
         cache_key = (start, end)
         cached = self._crop_cache.get(cache_key)
         if cached is not None:

src/textual/widgets/_text_area.py

@@ -1236,9 +1236,7 @@ def render_line(self, y: int) -> Strip:
 
         # Crop the line to show only the visible part (some may be scrolled out of view)
         if not self.soft_wrap:
-            text_strip = text_strip.crop(
-                scroll_x, scroll_x + virtual_width - gutter_width
-            )
+            text_strip = text_strip.crop(scroll_x, scroll_x + virtual_width)
 
         # Stylize the line the cursor is currently on.
         if cursor_row == line_index:

tests/snapshot_tests/snapshot_apps/split_segments.py

@@ -0,0 +1,14 @@
+from textual.app import App, ComposeResult
+from textual.widgets import TextArea
+
+FAIL_TEXT = "x"
+
+
+class CodeApp(App):
+    def compose(self) -> ComposeResult:
+        yield TextArea(FAIL_TEXT, soft_wrap=False, show_line_numbers=True)
+
+
+if __name__ == "__main__":
+    app = CodeApp()
+    app.run()

tests/snapshot_tests/test_snapshots.py

@@ -2417,3 +2417,12 @@ def on_mount(self) -> None:
             self.mount(Label("HELLO"))
 
     assert snap_compare(PSApp())
+
+
+def test_split_segments_infinite_loop(snap_compare):
+    """Regression test for https://github.com/Textualize/textual/issues/5151
+
+    Should be a bare-bones text editor containing "x"
+
+    """
+    assert snap_compare(SNAPSHOT_APPS_DIR / "split_segments.py")

tests/test_strip.py

@@ -131,7 +131,7 @@ def test_crop():
 
     assert Strip([Segment("foo")]).crop(1, 3) == Strip([Segment("oo")])
     assert Strip([Segment("foo")]).crop(1, 2) == Strip([Segment("o")])
-    assert Strip([Segment("foo")]).crop(1, 1) == Strip([Segment("")])
+    assert Strip([Segment("foo")]).crop(1, 1) == Strip([])
 
     assert Strip([Segment("foo💩"), Segment("b💩ar"), Segment("ba💩z")]).crop(
         1, 6