scrollbar visibility rule

src/textual/_compositor.py

@@ -694,7 +694,7 @@ class Compositor:
                     if (
                         widget.show_vertical_scrollbar
                         or widget.show_horizontal_scrollbar
-                    ):
+                    ) and styles.scrollbar_visibility == "visible":
                         for chrome_widget, chrome_region in widget._arrange_scrollbars(
                             container_region
                         ):

src/textual/css/_styles_builder.py

@@ -52,6 +52,7 @@ from textual.css.constants import (
     VALID_OVERLAY,
     VALID_POSITION,
     VALID_SCROLLBAR_GUTTER,
+    VALID_SCROLLBAR_VISIBILITY,
     VALID_STYLE_FLAGS,
     VALID_TEXT_ALIGN,
     VALID_TEXT_OVERFLOW,
@@ -76,6 +77,7 @@ from textual.css.types import (
     Display,
     EdgeType,
     Overflow,
+    ScrollbarVisibility,
     TextOverflow,
     TextWrap,
     Visibility,
@@ -768,6 +770,13 @@ class StylesBuilder:
     process_scrollbar_background_hover = process_color
     process_scrollbar_background_active = process_color
 
+    def process_scrollbar_visibility(self, name: str, tokens: list[Token]) -> None:
+        """Process scrollbar visibility rules."""
+        self.styles._rules["scrollbar_visibility"] = cast(
+            ScrollbarVisibility,
+            self._process_enum(name, tokens, VALID_SCROLLBAR_VISIBILITY),
+        )
+
     process_link_color = process_color
     process_link_background = process_color
     process_link_color_hover = process_color

src/textual/css/constants.py

@@ -90,6 +90,7 @@ VALID_HATCH: Final = {"left", "right", "cross", "vertical", "horizontal"}
 VALID_TEXT_WRAP: Final = {"wrap", "nowrap"}
 VALID_TEXT_OVERFLOW: Final = {"clip", "fold", "ellipsis"}
 VALID_EXPAND: Final = {"greedy", "optimal"}
+VALID_SCROLLBAR_VISIBILITY: Final = {"visible", "hidden"}
 
 HATCHES: Final = {
     "left": "╲",

src/textual/css/styles.py

@@ -48,6 +48,7 @@ from textual.css.constants import (
     VALID_OVERLAY,
     VALID_POSITION,
     VALID_SCROLLBAR_GUTTER,
+    VALID_SCROLLBAR_VISIBILITY,
     VALID_TEXT_ALIGN,
     VALID_TEXT_OVERFLOW,
     VALID_TEXT_WRAP,
@@ -153,11 +154,10 @@ class RulesMap(TypedDict, total=False):
     scrollbar_background: Color
     scrollbar_background_hover: Color
     scrollbar_background_active: Color
-
     scrollbar_gutter: ScrollbarGutter
-
     scrollbar_size_vertical: int
     scrollbar_size_horizontal: int
+    scrollbar_visibility: ScrollbarVisibility
 
     align_horizontal: AlignHorizontal
     align_vertical: AlignVertical
@@ -242,6 +242,7 @@ class StylesBase:
         "scrollbar_background",
         "scrollbar_background_hover",
         "scrollbar_background_active",
+        "scrollbar_visibility",
         "link_color",
         "link_background",
         "link_color_hover",
@@ -424,6 +425,10 @@ class StylesBase:
     """Set the width of the vertical scrollbar (measured in cells)."""
     scrollbar_size_horizontal = IntegerProperty(default=1, layout=True)
     """Set the height of the horizontal scrollbar (measured in cells)."""
+    scrollbar_visibility = StringEnumProperty(
+        VALID_SCROLLBAR_VISIBILITY, "visible", layout=True
+    )
+    """Sets the visibility of the scrollbar."""
 
     align_horizontal = StringEnumProperty(
         VALID_ALIGN_HORIZONTAL, "left", layout=True, refresh_children=True
@@ -1153,6 +1158,8 @@ class Styles(StylesBase):
                 append_declaration(
                     "scrollbar-size-vertical", str(self.scrollbar_size_vertical)
                 )
+        if "scrollbar_visibility" in rules:
+            append_declaration("scrollbar-visibility", self.scrollbar_visibility)
 
         if "box_sizing" in rules:
             append_declaration("box-sizing", self.box_sizing)

src/textual/css/types.py

@@ -44,6 +44,7 @@ Position = Literal["relative", "absolute"]
 TextWrap = Literal["wrap", "nowrap"]
 TextOverflow = Literal["clip", "fold", "ellipsis"]
 Expand = Literal["greedy", "expand"]
+ScrollbarVisibility = Literal["visible", "hidden"]
 
 Specificity3 = Tuple[int, int, int]
 Specificity6 = Tuple[int, int, int, int, int, int]

src/textual/dom.py

@@ -1723,8 +1723,6 @@ class DOMNode(MessagePump):
 
         Should be called whenever CSS classes / pseudo classes change.
         """
-        if not self.is_attached or not self.screen.is_mounted:
-            return
         try:
             self.app.update_styles(self)
         except NoActiveAppError:

src/textual/widget.py

@@ -346,7 +346,7 @@ class Widget(DOMNode):
     loading: Reactive[bool] = Reactive(False)
     """If set to `True` this widget will temporarily be replaced with a loading indicator."""
 
-    virtual_size: Reactive[Size] = Reactive(Size(0, 0), layout=True)
+    virtual_size: Reactive[Size] = Reactive(Size(0, 0), layout=True, repaint=False)
     """The virtual (scrollable) [size][textual.geometry.Size] of the widget."""
 
     has_focus: Reactive[bool] = Reactive(False, repaint=False)
@@ -3421,6 +3421,7 @@ class Widget(DOMNode):
             `True` if any scrolling has occurred in any descendant, otherwise `False`.
         """
         # Grow the region by the margin so to keep the margin in view.
+
         region = widget.virtual_region_with_margin
         scrolled = False
 
@@ -3430,7 +3431,11 @@ class Widget(DOMNode):
             return False
 
         while isinstance(widget.parent, Widget) and widget is not self:
+            if not region:
+                break
+
             container = widget.parent
+
             if widget.styles.dock != "none":
                 scroll_offset = Offset(0, 0)
             else:
@@ -3454,13 +3459,11 @@ class Widget(DOMNode):
 
             # Adjust the region by the amount we just scrolled it, and convert to
             # its parent's virtual coordinate system.
-
             region = (
                 (
                     region.translate(-scroll_offset)
                     .translate(container.styles.margin.top_left)
                     .translate(container.styles.border.spacing.top_left)
-                    .translate(-widget.scroll_offset)
                     .translate(container.virtual_region_with_margin.offset)
                 )
                 .grow(container.styles.margin)