expose smooth scrolling

Author: willmcgugan

src/textual/app.py

@@ -795,6 +795,9 @@ def __init__(
         self._clipboard: str = ""
         """Contents of local clipboard."""
 
+        self.supports_smooth_scrolling: bool = True
+        """Does the terminal support smooth scrolling?"""
+
         if self.ENABLE_COMMAND_PALETTE:
             for _key, binding in self._bindings:
                 if binding.action in {"command_palette", "app.command_palette"}:
@@ -4632,6 +4635,7 @@ def _on_terminal_supports_in_band_window_resize(
         """There isn't much we can do with this information currently, so
         we will just log it.
         """
+        self.supports_smooth_scrolling = True
         self.log.debug(message)
 
     def _on_idle(self) -> None:

src/textual/constants.py

@@ -159,5 +159,5 @@ def _get_textual_animations() -> AnimationLevel:
 """
 
 SMOOTH_SCROLL: Final[bool] = _get_environ_int("TEXTUAL_SMOOTH_SCROLL", 1) == 1
-"""Should smooth scrolling be enabled? set `TEXTUAL_SMOOTH_SCROLL=0` to disable smooth scrolling.
+"""Should smooth scrolling be enabled? set `TEXTUAL_SMOOTH_SCROLL=0` to disable smooth
 """

src/textual/widget.py

@@ -1693,26 +1693,26 @@ def watch_hover_style(
             self.highlight_link_id = hover_style.link_id
 
     def watch_scroll_x(self, old_value: float, new_value: float) -> None:
-        self.horizontal_scrollbar.position = round(new_value)
-        if (old_value) != (new_value):
+        self.horizontal_scrollbar.position = new_value
+        if round(old_value) != round(new_value):
             self._refresh_scroll()
 
     def watch_scroll_y(self, old_value: float, new_value: float) -> None:
-        self.vertical_scrollbar.position = round(new_value)
-        if (old_value) != (new_value):
+        self.vertical_scrollbar.position = new_value
+        if round(old_value) != round(new_value):
             self._refresh_scroll()
 
     def validate_scroll_x(self, value: float) -> float:
         return clamp(value, 0, self.max_scroll_x)
 
     def validate_scroll_target_x(self, value: float) -> float:
-        return clamp(value, 0, self.max_scroll_x)
+        return round(clamp(value, 0, self.max_scroll_x))
 
     def validate_scroll_y(self, value: float) -> float:
         return clamp(value, 0, self.max_scroll_y)
 
     def validate_scroll_target_y(self, value: float) -> float:
-        return clamp(value, 0, self.max_scroll_y)
+        return round(clamp(value, 0, self.max_scroll_y))
 
     @property
     def max_scroll_x(self) -> int: