gemoetry split

sandbox/uber.py

@@ -20,17 +20,20 @@ class BasicApp(App):
             Widget(id="uber2-child2"),
         )
 
+        uber1 = Widget(
+            Placeholder(id="child1", classes={"list-item"}),
+            Placeholder(id="child2", classes={"list-item"}),
+            Placeholder(id="child3", classes={"list-item"}),
+            Placeholder(classes={"list-item"}),
+            Placeholder(classes={"list-item"}),
+            Placeholder(classes={"list-item"}),
+            Placeholder(classes={"list-item"}),
+            # Placeholder(id="child3", classes={"list-item"}),
+        )
+        uber1.show_vertical_scrollbar = True
+
         self.mount(
-            uber1=Widget(
+            uber1=uber1
-                Placeholder(id="child1", classes={"list-item"}),
-                Placeholder(id="child2", classes={"list-item"}),
-                Placeholder(id="child3", classes={"list-item"}),
-                Placeholder(classes={"list-item"}),
-                Placeholder(classes={"list-item"}),
-                Placeholder(classes={"list-item"}),
-                Placeholder(classes={"list-item"}),
-                # Placeholder(id="child3", classes={"list-item"}),
-            ),
             # uber2=uber2,
         )
 

src/textual/_compositor.py

@@ -13,6 +13,7 @@ from rich.style import Style
 from . import errors, log
 from .geometry import Region, Offset, Size
 
+from ._arrange import arrange
 from ._loop import loop_last
 from ._types import Lines
 from .widget import Widget
@@ -88,15 +89,20 @@ class Compositor:
         # All widgets considered in the arrangement
         # Not this may be a supperset of self.map.keys() as some widgets may be invisible for various reasons
         self.widgets: set[Widget] = set()
+
+        # The top level widget
         self.root: Widget | None = None
 
         # Dimensions of the arrangement
         self.size = Size(0, 0)
 
+        # A mapping of Widget on to region, and clip region
+        # The clip region can be considered the window through which a widget is viewed
         self.regions: dict[Widget, tuple[Region, Region]] = {}
+
+        # The points in each line where the line bisects the left and right edges of the widget
         self._cuts: list[list[int]] | None = None
         self._require_update: bool = True
-        self.background = ""
 
     def __rich_repr__(self) -> rich.repr.Result:
         yield "size", self.size
@@ -202,9 +208,15 @@ class Compositor:
                 total_region = region.size.region
                 sub_clip = clip.intersection(region)
 
-                placements, arranged_widgets = widget.layout.arrange(
+                # for chrome_widget, chrome_region in widget.arrange_chrome(region.size):
-                    widget, region.size, scroll
+                #     map[chrome_widget] = RenderRegion(
-                )
+                #         chrome_region + layout_offset,
+                #         order,
+                #         clip,
+                #         total_region.size,
+                #     )
+
+                placements, arranged_widgets = arrange(widget, region.size, scroll)
 
                 widgets.update(arranged_widgets)
                 placements = sorted(placements, key=attrgetter("order"))
@@ -219,6 +231,16 @@ class Compositor:
                             sub_clip,
                         )
 
+                for chrome_widget, chrome_region in widget.arrange_chrome(region.size):
+                    render_region = RenderRegion(
+                        chrome_region + region.origin + layout_offset,
+                        order,
+                        clip,
+                        total_region.size,
+                    )
+                    log(render_region)
+                    map[chrome_widget] = render_region
+
             map[widget] = RenderRegion(
                 region + layout_offset, order, clip, total_region.size
             )
@@ -245,8 +267,9 @@ class Compositor:
 
     def get_widget_at(self, x: int, y: int) -> tuple[Widget, Region]:
         """Get the widget under the given point or None."""
+        contains = Region.contains
         for widget, cropped_region, region, _ in self:
-            if cropped_region.contains(x, y):
+            if contains(cropped_region, x, y):
                 return widget, region
         raise errors.NoWidget(f"No widget under screen coordinate ({x}, {y})")
 
@@ -345,7 +368,7 @@ class Compositor:
                 [
                     (widget, region, order, clip)
                     for widget, (region, order, clip, _) in self.map.items()
-                    if widget.visible
+                    if widget.visible and not widget.is_transparent
                 ],
                 key=itemgetter(2),
                 reverse=True,
@@ -355,14 +378,12 @@ class Compositor:
 
         divide = Segment.divide
         intersection = Region.intersection
+        overlaps = Region.overlaps
 
         for widget, region, _order, clip in widget_regions:
-            if widget.is_transparent:
-                continue
             if region in clip:
-                lines = widget._get_lines()
+                yield region, clip, widget._get_lines()
-                yield region, clip, lines
+            elif overlaps(clip, region):
-            elif clip.overlaps(region):
                 lines = widget._get_lines()
                 new_x, new_y, new_width, new_height = intersection(region, clip)
                 delta_x = new_x - region.x
@@ -377,7 +398,7 @@ class Compositor:
         cls, chops: list[dict[int, list[Segment] | None]]
     ) -> list[list[Segment]]:
 
-        # Pretty sure we don't need to sort the buck items
+        # Pretty sure we don't need to sort the bucket items
         segment_lines = [
             sum(
                 [line for line in bucket.values() if line is not None],
@@ -432,6 +453,7 @@ class Compositor:
                 first_cut, last_cut = render_region.x_extents
                 final_cuts = [cut for cut in cuts[y] if (last_cut >= cut >= first_cut)]
 
+                # TODO: Suspect this may break for region not on cut boundaries
                 if len(final_cuts) == 2:
                     # Two cuts, which means the entire line
                     cut_segments = [line]
@@ -440,8 +462,8 @@ class Compositor:
                     render_x = render_region.x
                     relative_cuts = [cut - render_x for cut in final_cuts]
                     _, *cut_segments = divide(line, relative_cuts)
-                # Since we are painting front to back, the first segments for a cut "wins"
 
+                # Since we are painting front to back, the first segments for a cut "wins"
                 chops_line = chops[y]
                 for cut, segments in zip(final_cuts, cut_segments):
                     if chops_line[cut] is None:

src/textual/geometry.py

@@ -488,6 +488,95 @@ class Region(NamedTuple):
         )
         return union_region
 
+    def split(self, cut_x: int, cut_y: int) -> tuple[Region, Region, Region, Region]:
+        """Split a region in to 4 from given x and y offsets (cuts).
+
+                   cut_x ↓
+                ┌────────┐┌───┐
+                │        ││   │
+                │        ││   │
+                │        ││   │
+        cut_y → └────────┘└───┘
+                ┌────────┐┌───┐
+                │        ││   │
+                └────────┘└───┘
+
+        Args:
+            cut_x (int): Offset from self.x where the cut should be made. If negative, the cut
+                is taken from the right edge.
+            cut_y (int): Offset from self.y where the cut should be made. If negative, the cut
+                is taken from the lower edge.
+
+        Returns:
+            tuple[Region, Region, Region, Region]: Four new regions which add up to the original (self).
+        """
+
+        x, y, width, height = self
+        if cut_x < 0:
+            cut_x = width + cut_x
+        if cut_y < 0:
+            cut_y = height + cut_y
+
+        _Region = Region
+        return (
+            _Region(x, y, cut_x, cut_y),
+            _Region(x + cut_x, y, width - cut_x, cut_y),
+            _Region(x, y + cut_y, cut_x, height - cut_y),
+            _Region(x + cut_x, y + cut_y, width - cut_x, height - cut_y),
+        )
+
+    def split_vertical(self, cut: int) -> tuple[Region, Region]:
+        """Split a region in to two, from a given x offset.
+
+                 cut ↓
+            ┌────────┐┌───┐
+            │        ││   │
+            │        ││   │
+            └────────┘└───┘
+
+        Args:
+            cut (int): An offset from self.x where the cut should be made. If cut is negative,
+                it is taken from the right edge.
+
+        Returns:
+            tuple[Region, Region]: Two regions, which add up to the original (self).
+        """
+
+        x, y, width, height = self
+        if cut < 0:
+            cut = width + cut
+
+        return (
+            Region(x, y, cut, height),
+            Region(x + cut, y, width - cut, height),
+        )
+
+    def split_horizontal(self, cut: int) -> tuple[Region, Region]:
+        """Split a region in to two, from a given x offset.
+
+                    ┌─────────┐
+                    │         │
+                    │         │
+            cut →   └─────────┘
+                    ┌─────────┐
+                    └─────────┘
+
+        Args:
+            cut (int): An offset from self.x where the cut should be made. May be negative,
+                for the offset to start from the right edge.
+
+        Returns:
+            tuple[Region, Region]: Two regions, which add up to the original (self).
+        """
+        x, y, width, height = self
+        if cut < 0:
+            cut = height + cut
+
+        return (
+            Region(x, y, width, cut),
+            Region(x, y + cut, width, height - cut),
+        )
+
 
 class Spacing(NamedTuple):
     """The spacing around a renderable."""

src/textual/layout.py

@@ -48,7 +48,7 @@ class Layout(ABC):
     @abstractmethod
     def arrange(
         self, parent: Widget, size: Size, scroll: Offset
-    ) -> tuple[Iterable[WidgetPlacement], set[Widget]]:
+    ) -> tuple[list[WidgetPlacement], set[Widget]]:
         """Generate a layout map that defines where on the screen the widgets will be drawn.
 
         Args:

src/textual/layouts/dock.py

@@ -61,7 +61,7 @@ class DockLayout(Layout):
 
     def arrange(
         self, parent: Widget, size: Size, scroll: Offset
-    ) -> tuple[Iterable[WidgetPlacement], set[Widget]]:
+    ) -> tuple[list[WidgetPlacement], set[Widget]]:
 
         width, height = size
         layout_region = Region(0, 0, width, height)

src/textual/layouts/horizontal.py

@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-from typing import Iterable
-
 
 from textual.geometry import Size, Offset, Region
 from textual.layout import Layout, WidgetPlacement
@@ -27,11 +25,9 @@ class HorizontalLayout(Layout):
         parent_size = parent.size
 
         for widget in parent.children:
-
             (content_width, content_height), margin = widget.styles.get_box_model(
                 size, parent_size
             )
-
             region = Region(margin.left + x, margin.top, content_width, content_height)
             max_height = max(max_height, content_height + margin.height)
             add_placement(WidgetPlacement(region, widget, 0))

src/textual/layouts/vertical.py

@@ -27,11 +27,9 @@ class VerticalLayout(Layout):
         parent_size = parent.size
 
         for widget in parent.children:
-
             (content_width, content_height), margin = widget.styles.get_box_model(
                 size, parent_size
             )
-
             region = Region(margin.left, y + margin.top, content_width, content_height)
             max_width = max(max_width, content_width + margin.width)
             add_placement(WidgetPlacement(region, widget, 0))

src/textual/screen.py

@@ -95,10 +95,12 @@ class Screen(Widget):
         try:
             hidden, shown, resized = self._compositor.reflow(self, self.size)
 
+            Hide = events.Hide
+            Show = events.Show
             for widget in hidden:
-                widget.post_message_no_wait(events.Hide(self))
+                widget.post_message_no_wait(Hide(self))
             for widget in shown:
-                widget.post_message_no_wait(events.Show(self))
+                widget.post_message_no_wait(Show(self))
 
             send_resize = shown | resized
 

src/textual/scrollbar.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import rich.repr
 from rich.color import Color
 from rich.console import ConsoleOptions, RenderResult, RenderableType
-from rich.segment import Segment
+from rich.segment import Segment, Segments
 from rich.style import Style, StyleType
 
 from textual.reactive import Reactive

src/textual/widget.py

@@ -36,8 +36,10 @@ from .layout import Layout
 from .reactive import Reactive, watch
 from .renderables.opacity import Opacity
 
+
 if TYPE_CHECKING:
     from .screen import Screen
+    from .scrollbar import ScrollBar
 
 
 class RenderCache(NamedTuple):
@@ -79,6 +81,9 @@ class Widget(DOMNode):
         self.render_cache: RenderCache | None = None
         self.highlight_style: Style | None = None
 
+        self._vertical_scrollbar: ScrollBar | None = None
+        self._horizontal_scrollbar: ScrollBar | None = None
+
         super().__init__(name=name, id=id, classes=classes)
         self.add_children(*children)
 
@@ -87,6 +92,54 @@ class Widget(DOMNode):
     scroll_x = Reactive(0)
     scroll_y = Reactive(0)
     virtual_size = Reactive(Size(0, 0))
+    show_vertical_scrollbar = Reactive(False)
+    show_horizontal_scrollbar = Reactive(False)
+
+    @property
+    def vertical_scrollbar(self) -> ScrollBar:
+        """Get a vertical scrollbar (create if necessary)
+
+        Returns:
+            ScrollBar: ScrollBar Widget.
+        """
+        from .scrollbar import ScrollBar
+
+        if self._vertical_scrollbar is not None:
+            return self._vertical_scrollbar
+        self._vertical_scrollbar = scroll_bar = ScrollBar(
+            vertical=True, name="vertical"
+        )
+        self.app.register(self, scroll_bar)
+        return scroll_bar
+
+    @property
+    def horizontal_scrollbar(self) -> ScrollBar:
+        """Get a vertical scrollbar (create if necessary)
+
+        Returns:
+            ScrollBar: ScrollBar Widget.
+        """
+        from .scrollbar import ScrollBar
+
+        if self._horizontal_scrollbar is not None:
+            return self._horizontal_scrollbar
+        self._horizontal_scrollbar = scroll_bar = ScrollBar(
+            vertical=True, name="vertical"
+        )
+        self.app.register(self, scroll_bar)
+        return scroll_bar
+
+    @property
+    def scrollbars_enabled(self) -> tuple[bool, bool]:
+        """A tuple of booleans that indicate if scrollbars are enabled.
+
+        Returns:
+            tuple[bool, bool]: A tuple of (<vertical scrollbar enabled>, <horizontal scrollbar enabled>)
+
+        """
+        if self.layout is None:
+            return False, False
+        return self.show_vertical_scrollbar, self.show_horizontal_scrollbar
 
     def __init_subclass__(cls, can_focus: bool = True) -> None:
         super().__init_subclass__()
@@ -102,6 +155,30 @@ class Widget(DOMNode):
         if pseudo_classes:
             yield "pseudo_classes", set(pseudo_classes)
 
+    def arrange_chrome(self, size: Size) -> Iterable[tuple[Widget, Region]]:
+        region = size.region
+        show_vertical_scrollbar, show_horizontal_scrollbar = self.scrollbars_enabled
+
+        if show_horizontal_scrollbar and show_vertical_scrollbar:
+            (
+                region,
+                vertical_scrollbar_region,
+                horizontal_scrollbar_region,
+                _,
+            ) = region.split(-1, -1)
+            if vertical_scrollbar_region:
+                yield self.vertical_scrollbar, vertical_scrollbar_region
+            if horizontal_scrollbar_region:
+                yield self.horizontal_scrollbar, horizontal_scrollbar_region
+        elif show_vertical_scrollbar:
+            region, scrollbar_region = region.split_vertical(-1)
+            if scrollbar_region:
+                yield self.vertical_scrollbar, scrollbar_region
+        elif show_horizontal_scrollbar:
+            region, scrollbar_region = region.split_horizontal(-1)
+            if scrollbar_region:
+                yield self.horizontal_scrollbar, scrollbar_region
+
     def get_pseudo_classes(self) -> Iterable[str]:
         """Pseudo classes for a widget"""
         if self._mouse_over:

src/textual/widgets/_static.py

@@ -11,11 +11,14 @@ class Static(Widget):
     def __init__(
         self,
         renderable: RenderableType,
+        *,
         name: str | None = None,
+        id: str | None = None,
+        classes: set[str] | None = None,
         style: StyleType = "",
         padding: PaddingDimensions = 0,
     ) -> None:
-        super().__init__(name)
+        super().__init__(name=name, id=id, classes=classes)
         self.renderable = renderable
         self.style = style
         self.padding = padding

tests/test_geometry.py

@@ -307,3 +307,49 @@ def test_spacing_add():
 
     with pytest.raises(TypeError):
         Spacing(1, 2, 3, 4) + "foo"
+
+
+def test_split():
+    assert Region(10, 5, 22, 15).split(10, 5) == (
+        Region(10, 5, 10, 5),
+        Region(20, 5, 12, 10),
+        Region(10, 10, 10, 10),
+        Region(20, 10, 10, 5),
+    )
+
+
+def test_split_negative():
+    assert Region(10, 5, 22, 15).split(-1, -1) == (
+        Region(10, 5, 21, 14),
+        Region(31, 5, 1, 14),
+        Region(10, 19, 21, 1),
+        Region(31, 19, 1, 1),
+    )
+
+
+def test_split_vertical():
+    assert Region(10, 5, 22, 15).split_vertical(10) == (
+        Region(10, 5, 10, 15),
+        Region(20, 5, 12, 15),
+    )
+
+
+def test_split_vertical_negative():
+    assert Region(10, 5, 22, 15).split_vertical(-1) == (
+        Region(10, 5, 21, 15),
+        Region(31, 5, 1, 15),
+    )
+
+
+def test_split_horizontal():
+    assert Region(10, 5, 22, 15).split_horizontal(5) == (
+        Region(10, 5, 22, 5),
+        Region(10, 10, 22, 10),
+    )
+
+
+def test_split_horizontal_negative():
+    assert Region(10, 5, 22, 15).split_horizontal(-1) == (
+        Region(10, 5, 22, 14),
+        Region(10, 19, 22, 1),
+    )