[css] Add the management of a "blank" value for our borders

sandbox/borders.py

@@ -0,0 +1,65 @@
+from rich.console import RenderableType
+from rich.text import Text
+
+from textual.app import App, ComposeResult
+from textual.css.types import EdgeType
+from textual.widget import Widget
+from textual.widgets import Placeholder
+
+
+class VerticalContainer(Widget):
+    CSS = """
+    VerticalContainer {
+        layout: vertical;
+        overflow: hidden auto;
+        background: darkblue;
+    }
+
+    VerticalContainer Placeholder {
+        margin: 1 0;
+        height: 5;
+        align: center top;
+    }
+    """
+
+
+class Introduction(Widget):
+    CSS = """
+    Introduction {
+        background: indigo;
+        color: white;
+        height: 3;
+        padding: 1 0;
+    }
+    """
+
+    def render(self, styles) -> RenderableType:
+        return Text("Here are the color edge types we support.", justify="center")
+
+
+class MyTestApp(App):
+    def compose(self) -> ComposeResult:
+        placeholders = []
+        for border_edge_type in EdgeType.__args__:
+            border_placeholder = Placeholder(
+                id=f"placeholder_{border_edge_type}",
+                title=(border_edge_type or " ").upper(),
+                name=f"border: {border_edge_type} white",
+            )
+            border_placeholder.styles.border = (border_edge_type, "white")
+            placeholders.append(border_placeholder)
+
+        yield VerticalContainer(Introduction(), *placeholders, id="root")
+
+    def on_mount(self):
+        self.bind("q", "quit")
+        self.bind("t", "tree")
+
+    def action_tree(self):
+        self.log(self.tree)
+
+
+app = MyTestApp()
+
+if __name__ == "__main__":
+    app.run()

src/textual/_border.py

@@ -5,9 +5,8 @@ from functools import lru_cache
 from rich.console import Console, ConsoleOptions, RenderResult, RenderableType
 import rich.repr
 from rich.segment import Segment, SegmentLines
-from rich.style import Style, StyleType
+from rich.style import Style
 
-from .color import Color
 from .css.types import EdgeStyle, EdgeType
 
 
@@ -15,10 +14,14 @@ INNER = 1
 OUTER = 2
 
 BORDER_CHARS: dict[EdgeType, tuple[str, str, str]] = {
-    # TODO: in "browsers' CSS" `none` and `hidden` both set the border width to zero. Should we do the same?
+    # Each string of the tuple represents a sub-tuple itself:
+    #  - 1st string represents `(top1, top2, top3)`
+    #  - 2nd string represents (mid1, mid2, mid3)
+    #  - 3rd string represents (bottom1, bottom2, bottom3)
     "": ("   ", "   ", "   "),
     "none": ("   ", "   ", "   "),
     "hidden": ("   ", "   ", "   "),
+    "blank": ("   ", "   ", "   "),
     "round": ("╭─╮", "│ │", "╰─╯"),
     "solid": ("┌─┐", "│ │", "└─┘"),
     "double": ("╔═╗", "║ ║", "╚═╝"),
@@ -40,6 +43,7 @@ BORDER_LOCATIONS: dict[
     "": ((0, 0, 0), (0, 0, 0), (0, 0, 0)),
     "none": ((0, 0, 0), (0, 0, 0), (0, 0, 0)),
     "hidden": ((0, 0, 0), (0, 0, 0), (0, 0, 0)),
+    "blank": ((0, 0, 0), (0, 0, 0), (0, 0, 0)),
     "round": ((0, 0, 0), (0, 0, 0), (0, 0, 0)),
     "solid": ((0, 0, 0), (0, 0, 0), (0, 0, 0)),
     "double": ((0, 0, 0), (0, 0, 0), (0, 0, 0)),
@@ -53,6 +57,8 @@ BORDER_LOCATIONS: dict[
     "wide": ((1, 1, 1), (0, 1, 0), (1, 1, 1)),
 }
 
+_INVISIBLE_EDGE_TYPES: tuple[EdgeType, ...] = ("none", "hidden")
+
 
 @lru_cache(maxsize=1024)
 def get_box(
@@ -135,7 +141,12 @@ class Border:
             (bottom, bottom_color),
             (left, left_color),
         ) = edge_styles
-        self._sides = (top or "none", right or "none", bottom or "none", left or "none")
+        self._sides: tuple[EdgeType, ...] = (
+            top or "none",
+            right or "none",
+            bottom or "none",
+            left or "none",
+        )
         from_color = Style.from_color
 
         self._styles = (
@@ -159,10 +170,10 @@ class Border:
             width (int): Desired width.
         """
         top, right, bottom, left = self._sides
-        has_left = left != "none"
-        has_right = right != "none"
-        has_top = top != "none"
-        has_bottom = bottom != "none"
+        has_left = left not in _INVISIBLE_EDGE_TYPES
+        has_right = right not in _INVISIBLE_EDGE_TYPES
+        has_top = top not in _INVISIBLE_EDGE_TYPES
+        has_bottom = bottom not in _INVISIBLE_EDGE_TYPES
 
         if has_top:
             lines.pop(0)
@@ -188,10 +199,10 @@ class Border:
         outer_style = console.get_style(self.outer_style)
         top_style, right_style, bottom_style, left_style = self._styles
 
-        has_left = left != "none"
-        has_right = right != "none"
-        has_top = top != "none"
-        has_bottom = bottom != "none"
+        has_left = left not in _INVISIBLE_EDGE_TYPES
+        has_right = right not in _INVISIBLE_EDGE_TYPES
+        has_top = top not in _INVISIBLE_EDGE_TYPES
+        has_bottom = bottom not in _INVISIBLE_EDGE_TYPES
 
         width = options.max_width - has_left - has_right
 

src/textual/css/constants.py

@@ -1,4 +1,6 @@
+from __future__ import annotations
 import sys
+import typing
 
 if sys.version_info >= (3, 8):
     from typing import Final
@@ -7,12 +9,16 @@ else:
 
 from ..geometry import Spacing
 
+if typing.TYPE_CHECKING:
+    from .types import EdgeType
+
 VALID_VISIBILITY: Final = {"visible", "hidden"}
 VALID_DISPLAY: Final = {"block", "none"}
-VALID_BORDER: Final = {
+VALID_BORDER: Final[set[EdgeType]] = {
     "none",
     "hidden",
     "round",
+    "blank",
     "solid",
     "double",
     "dashed",

src/textual/css/types.py

@@ -16,6 +16,7 @@ EdgeType = Literal[
     "",
     "none",
     "hidden",
+    "blank",
     "round",
     "solid",
     "double",
@@ -35,6 +36,6 @@ AlignVertical = Literal["top", "middle", "bottom"]
 ScrollbarGutter = Literal["auto", "stable"]
 BoxSizing = Literal["border-box", "content-box"]
 Overflow = Literal["scroll", "hidden", "auto"]
-EdgeStyle = Tuple[str, Color]
+EdgeStyle = Tuple[EdgeType, Color]
 Specificity3 = Tuple[int, int, int]
 Specificity4 = Tuple[int, int, int, int]

src/textual/widgets/_placeholder.py

@@ -19,6 +19,19 @@ class Placeholder(Widget, can_focus=True):
     has_focus: Reactive[bool] = Reactive(False)
     mouse_over: Reactive[bool] = Reactive(False)
 
+    def __init__(
+        # parent class constructor signature:
+        self,
+        *children: Widget,
+        name: str | None = None,
+        id: str | None = None,
+        classes: str | None = None,
+        # ...and now for our own class specific params:
+        title: str | None = None,
+    ) -> None:
+        super().__init__(*children, name=name, id=id, classes=classes)
+        self.title = title
+
     def __rich_repr__(self) -> rich.repr.Result:
         yield from super().__rich_repr__()
         yield "has_focus", self.has_focus, False
@@ -32,7 +45,7 @@ class Placeholder(Widget, can_focus=True):
                 Pretty(self, no_wrap=True, overflow="ellipsis"),
                 vertical="middle",
             ),
-            title=self.__class__.__name__,
+            title=self.title or self.__class__.__name__,
             border_style="green" if self.mouse_over else "blue",
             box=box.HEAVY if self.has_focus else box.ROUNDED,
         )