Merge pull request #5164 from Textualize/list-view-fix

Fix list view flicker

CHANGELOG.md

@@ -22,6 +22,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added `Containers.HorizontalGroup` and `Containers.VerticalGroup` https://github.com/Textualize/textual/pull/5113
 - Added `$`, `£`, `€`, `(`, `)` symbols to Digits https://github.com/Textualize/textual/pull/5113
 - Added `Button.action` parameter to invoke action when clicked https://github.com/Textualize/textual/pull/5113
+- Added `immediate` parameter to scroll methods https://github.com/Textualize/textual/pull/5164
+- Added `textual._loop.loop_from_index` https://github.com/Textualize/textual/pull/5164
+
+### Fixed
+
+- Fixed glitchy ListView https://github.com/Textualize/textual/issues/5163
 
 ## [0.84.0] - 2024-10-22
 

src/textual/_loop.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import Iterable, TypeVar
+from typing import Iterable, Literal, Sequence, TypeVar
 
 T = TypeVar("T")
 
@@ -43,3 +43,44 @@ def loop_first_last(values: Iterable[T]) -> Iterable[tuple[bool, bool, T]]:
         first = False
         previous_value = value
     yield first, True, previous_value
+
+
+def loop_from_index(
+    values: Sequence[T],
+    index: int,
+    direction: Literal[-1, +1] = +1,
+    wrap: bool = True,
+) -> Iterable[tuple[int, T]]:
+    """Iterate over values in a sequence from a given starting index, potentially wrapping the index
+    if it would go out of bounds.
+
+    Note that the first value to be yielded is a step from `index`, and `index` will be yielded *last*.
+
+
+    Args:
+        values: A sequence of values.
+        index: Starting index.
+        direction: Direction to move index (+1 for forward, -1 for backward).
+        bool: Should the index wrap when out of bounds?
+
+    Yields:
+        A tuple of index and value from the sequence.
+    """
+    # Sanity check for devs who miss the typing errors
+    assert direction in (-1, +1), "direction must be -1 or +1"
+    count = len(values)
+    if wrap:
+        for _ in range(count):
+            index = (index + direction) % count
+            yield (index, values[index])
+    else:
+        if direction == +1:
+            for _ in range(count):
+                if (index := index + 1) >= count:
+                    break
+                yield (index, values[index])
+        else:
+            for _ in range(count):
+                if (index := index - 1) < 0:
+                    break
+                yield (index, values[index])

src/textual/_profile.py

@@ -16,4 +16,4 @@ def timer(subject: str = "time") -> Generator[None, None, None]:
     yield
     elapsed = perf_counter() - start
     elapsed_ms = elapsed * 1000
-    log(f"{subject} elapsed {elapsed_ms:.2f}ms")
+    log(f"{subject} elapsed {elapsed_ms:.4f}ms")

src/textual/_widget_navigation.py

@@ -8,12 +8,13 @@
 
 from __future__ import annotations
 
-from functools import partial
 from itertools import count
 from typing import Literal, Protocol, Sequence
 
 from typing_extensions import TypeAlias
 
+from textual._loop import loop_from_index
+
 
 class Disableable(Protocol):
     """Non-widgets that have an enabled/disabled status."""
@@ -105,7 +106,6 @@ def find_next_enabled(
     candidates: Sequence[Disableable],
     anchor: int | None,
     direction: Direction,
-    with_anchor: bool = False,
 ) -> int | None:
     """Find the next enabled object if we're currently at the given anchor.
 
@@ -118,8 +118,6 @@ def find_next_enabled(
             enabled object.
         direction: The direction in which to traverse the candidates when looking for
             the next enabled candidate.
-        with_anchor: Consider the anchor position as the first valid position instead of
-            the last one.
 
     Returns:
         The next enabled object. If none are available, return the anchor.
@@ -134,17 +132,10 @@ def find_next_enabled(
             )
         return None
 
-    start = anchor + direction if not with_anchor else anchor
-    key_function = partial(
-        get_directed_distance,
-        start=start,
-        direction=direction,
-        wrap_at=len(candidates),
-    )
-    enabled_candidates = [
-        index for index, candidate in enumerate(candidates) if not candidate.disabled
-    ]
-    return min(enabled_candidates, key=key_function, default=anchor)
+    for index, candidate in loop_from_index(candidates, anchor, direction, wrap=True):
+        if not candidate.disabled:
+            return index
+    return anchor
 
 
 def find_next_enabled_no_wrap(

src/textual/scroll_view.py

@@ -123,6 +123,7 @@ def scroll_to(
         force: bool = False,
         on_complete: CallbackType | None = None,
         level: AnimationLevel = "basic",
+        immediate: bool = False,
     ) -> None:
         """Scroll to a given (absolute) coordinate, optionally animating.
 
@@ -136,6 +137,8 @@ def scroll_to(
             force: Force scrolling even when prohibited by overflow styling.
             on_complete: A callable to invoke when the animation is finished.
             level: Minimum level required for the animation to take place (inclusive).
+            immediate: If `False` the scroll will be deferred until after a screen refresh,
+                set to `True` to scroll immediately.
         """
 
         self._scroll_to(