added line_trim

src/textual/_segment_tools.py

@@ -9,7 +9,9 @@ from rich.segment import Segment
 from ._cells import cell_len
 
 
-def line_crop(segments: list[Segment], start: int, end: int, total: int):
+def line_crop(
+    segments: list[Segment], start: int, end: int, total: int
+) -> list[Segment]:
     """Crops a list of segments between two cell offsets.
 
     Args:
@@ -58,3 +60,31 @@ def line_crop(segments: list[Segment], start: int, end: int, total: int):
         segment = next(iter_segments, None)
 
     return output_segments
+
+
+def line_trim(segments: list[Segment], start: bool, end: bool) -> list[Segment]:
+    """Optionally remove a cell from the start and / or end of a list of segments.
+
+    Args:
+        segments (list[Segment]): A line (list of Segments)
+        start (bool): Remove cell from start.
+        end (bool): Remove cell from end.
+
+    Returns:
+        list[Segment]: A new list of segments.
+    """
+    segments = segments.copy()
+    if segments and start:
+        _, first_segment = segments[0].split_cells(1)
+        if first_segment.text:
+            segments[0] = first_segment
+        else:
+            segments.pop(0)
+    if segments and end:
+        last_segment = segments[-1]
+        last_segment, _ = last_segment.split_cells(len(last_segment.text) - 1)
+        if last_segment.text:
+            segments[-1] = last_segment
+        else:
+            segments.pop(-1)
+    return segments

tests/test_segment_tools.py

@@ -2,7 +2,7 @@ from rich.segment import Segment
 from rich.style import Style
 
 
-from textual._segment_tools import line_crop
+from textual._segment_tools import line_crop, line_trim
 
 
 def test_line_crop():
@@ -62,3 +62,30 @@ def test_line_crop_edge_2():
     expected = []
     print(repr(result))
     assert result == expected
+
+
+def test_line_trim():
+    segments = [Segment("foo")]
+
+    assert line_trim(segments, False, False) == segments
+    assert line_trim(segments, True, False) == [Segment("oo")]
+    assert line_trim(segments, False, True) == [Segment("fo")]
+    assert line_trim(segments, True, True) == [Segment("o")]
+
+    fob_segments = [Segment("f"), Segment("o"), Segment("b")]
+
+    assert line_trim(fob_segments, True, False) == [
+        Segment("o"),
+        Segment("b"),
+    ]
+
+    assert line_trim(fob_segments, False, True) == [
+        Segment("f"),
+        Segment("o"),
+    ]
+
+    assert line_trim(fob_segments, True, True) == [
+        Segment("o"),
+    ]
+
+    assert line_trim([], True, True) == []