From 76b39747cafa4aa1910e3c35bdb801c87ee10619 Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenb900@gmail.com>
Date: Wed, 22 Jun 2022 14:02:24 +0100
Subject: [PATCH 1/7] Move files into darren sandbox

---
 sandbox/{ => darren}/file_search.py         |  0
 sandbox/{ => darren}/file_search.scss       |  0
 sandbox/{ => darren}/focus_keybindings.py   |  0
 sandbox/{ => darren}/focus_keybindings.scss |  0
 sandbox/{ => darren}/tabs.py                |  0
 sandbox/{ => darren}/tabs.scss              |  0
 sandbox/hsl.py                              | 11 -----------
 sandbox/hsl.scss                            |  5 -----
 8 files changed, 16 deletions(-)
 rename sandbox/{ => darren}/file_search.py (100%)
 rename sandbox/{ => darren}/file_search.scss (100%)
 rename sandbox/{ => darren}/focus_keybindings.py (100%)
 rename sandbox/{ => darren}/focus_keybindings.scss (100%)
 rename sandbox/{ => darren}/tabs.py (100%)
 rename sandbox/{ => darren}/tabs.scss (100%)
 delete mode 100644 sandbox/hsl.py
 delete mode 100644 sandbox/hsl.scss

diff --git a/sandbox/file_search.py b/sandbox/darren/file_search.py
similarity index 100%
rename from sandbox/file_search.py
rename to sandbox/darren/file_search.py
diff --git a/sandbox/file_search.scss b/sandbox/darren/file_search.scss
similarity index 100%
rename from sandbox/file_search.scss
rename to sandbox/darren/file_search.scss
diff --git a/sandbox/focus_keybindings.py b/sandbox/darren/focus_keybindings.py
similarity index 100%
rename from sandbox/focus_keybindings.py
rename to sandbox/darren/focus_keybindings.py
diff --git a/sandbox/focus_keybindings.scss b/sandbox/darren/focus_keybindings.scss
similarity index 100%
rename from sandbox/focus_keybindings.scss
rename to sandbox/darren/focus_keybindings.scss
diff --git a/sandbox/tabs.py b/sandbox/darren/tabs.py
similarity index 100%
rename from sandbox/tabs.py
rename to sandbox/darren/tabs.py
diff --git a/sandbox/tabs.scss b/sandbox/darren/tabs.scss
similarity index 100%
rename from sandbox/tabs.scss
rename to sandbox/darren/tabs.scss
diff --git a/sandbox/hsl.py b/sandbox/hsl.py
deleted file mode 100644
index 17c0d4f49..000000000
--- a/sandbox/hsl.py
+++ /dev/null
@@ -1,11 +0,0 @@
-from textual.app import App, ComposeResult
-from textual.widgets import Static
-
-
-class HSLApp(App):
-    def compose(self) -> ComposeResult:
-        yield Static(classes="box")
-
-
-app = HSLApp(css_path="hsl.scss", watch_css=True)
-app.run()
diff --git a/sandbox/hsl.scss b/sandbox/hsl.scss
deleted file mode 100644
index 78c0a495f..000000000
--- a/sandbox/hsl.scss
+++ /dev/null
@@ -1,5 +0,0 @@
-.box {
-  height: 1fr;
-  /*background: rgb(180,50, 50);*/
-  background: hsl(180,50%, 50%);
-}

From 71536364a4f0a6ff7202c7d81d763ec151641465 Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenb900@gmail.com>
Date: Wed, 22 Jun 2022 14:03:24 +0100
Subject: [PATCH 2/7] Copy buttons example into sandbox

---
 sandbox/darren/buttons.css |  4 ++++
 sandbox/darren/buttons.py  | 31 +++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)
 create mode 100644 sandbox/darren/buttons.css
 create mode 100644 sandbox/darren/buttons.py

diff --git a/sandbox/darren/buttons.css b/sandbox/darren/buttons.css
new file mode 100644
index 000000000..cedf20ded
--- /dev/null
+++ b/sandbox/darren/buttons.css
@@ -0,0 +1,4 @@
+Button {
+    padding-left: 1;
+    padding-right: 1;
+}
diff --git a/sandbox/darren/buttons.py b/sandbox/darren/buttons.py
new file mode 100644
index 000000000..daf1047a1
--- /dev/null
+++ b/sandbox/darren/buttons.py
@@ -0,0 +1,31 @@
+from textual import layout, events
+from textual.app import App, ComposeResult
+from textual.widgets import Button
+
+
+class ButtonsApp(App[str]):
+    def compose(self) -> ComposeResult:
+        yield layout.Vertical(
+            Button("default", id="foo"),
+            Button.success("success", id="bar"),
+            Button.warning("warning", id="baz"),
+            Button.error("error", id="baz"),
+        )
+
+    def handle_pressed(self, event: Button.Pressed) -> None:
+        self.app.bell()
+
+    async def on_key(self, event: events.Key) -> None:
+        await self.dispatch_key(event)
+
+    def key_d(self):
+        self.dark = not self.dark
+
+
+app = ButtonsApp(
+    log_path="textual.log", css_path="buttons.css", watch_css=True, log_verbosity=2
+)
+
+if __name__ == "__main__":
+    result = app.run()
+    print(repr(result))

From 7ebac6b860049547b729c18f273b42cfc0472ae2 Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenb900@gmail.com>
Date: Tue, 28 Jun 2022 13:52:58 +0100
Subject: [PATCH 3/7] Add wip test for user over widget css, use type alias

---
 sandbox/darren/just_a_box.css | 11 +++++++++++
 sandbox/darren/just_a_box.py  | 12 ++++++++++++
 src/textual/css/parse.py      |  3 ++-
 tests/css/test_stylesheet.py  | 21 +++++++++++++++++++++
 4 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 sandbox/darren/just_a_box.css
 create mode 100644 sandbox/darren/just_a_box.py

diff --git a/sandbox/darren/just_a_box.css b/sandbox/darren/just_a_box.css
new file mode 100644
index 000000000..1965ecb95
--- /dev/null
+++ b/sandbox/darren/just_a_box.css
@@ -0,0 +1,11 @@
+Screen {
+    layout: dock;
+    height: 100%;
+}
+
+#box {
+    height: 50%;
+    width: 50%;
+    align: center middle;
+    background: green;
+}
diff --git a/sandbox/darren/just_a_box.py b/sandbox/darren/just_a_box.py
new file mode 100644
index 000000000..2541c7b2b
--- /dev/null
+++ b/sandbox/darren/just_a_box.py
@@ -0,0 +1,12 @@
+from textual.app import App, ComposeResult
+from textual.widgets import Static
+
+
+class JustABox(App):
+    def compose(self) -> ComposeResult:
+        yield Static("Hello, World!", id="box")
+
+
+if __name__ == "__main__":
+    app = JustABox(css_path="just_a_box.css", watch_css=True)
+    app.run()
diff --git a/src/textual/css/parse.py b/src/textual/css/parse.py
index f3ce8d3f7..9052c3b1d 100644
--- a/src/textual/css/parse.py
+++ b/src/textual/css/parse.py
@@ -7,6 +7,7 @@ from typing import Iterator, Iterable
 from rich import print
 
 from textual.css.errors import UnresolvedVariableError
+from textual.css.types import Specificity3
 from ._styles_builder import StylesBuilder, DeclarationError
 from .model import (
     Declaration,
@@ -20,7 +21,7 @@ from .styles import Styles
 from .tokenize import tokenize, tokenize_declarations, Token, tokenize_values
 from .tokenizer import EOFError, ReferencedBy
 
-SELECTOR_MAP: dict[str, tuple[SelectorType, tuple[int, int, int]]] = {
+SELECTOR_MAP: dict[str, tuple[SelectorType, Specificity3]] = {
     "selector": (SelectorType.TYPE, (0, 0, 1)),
     "selector_start": (SelectorType.TYPE, (0, 0, 1)),
     "selector_class": (SelectorType.CLASS, (0, 1, 0)),
diff --git a/tests/css/test_stylesheet.py b/tests/css/test_stylesheet.py
index 6d4425b42..1727b2911 100644
--- a/tests/css/test_stylesheet.py
+++ b/tests/css/test_stylesheet.py
@@ -3,12 +3,15 @@ from typing import Any
 
 import pytest
 
+from tests.utilities.test_app import AppTest
+from textual.app import App, ComposeResult
 from textual.color import Color
 from textual.css._help_renderables import HelpText
 from textual.css.stylesheet import Stylesheet, StylesheetParseError
 from textual.css.tokenizer import TokenizeError
 from textual.dom import DOMNode
 from textual.geometry import Spacing
+from textual.widget import Widget
 
 
 def _make_stylesheet(css: str) -> Stylesheet:
@@ -101,6 +104,24 @@ def test_stylesheet_apply_empty_rulesets():
     stylesheet.apply(node)
 
 
+@pytest.mark.xfail(reason="wip")
+def test_stylesheet_apply_user_css_over_widget_css():
+    user_css = ".a {color: red;}"
+
+    class MyWidget(Widget):
+        CSS = ".a {color: blue;}"
+
+    node = MyWidget()
+    node.add_class("a")
+
+    print(node.styles.color)
+    stylesheet = _make_stylesheet(user_css)
+    stylesheet.apply(node)
+
+    assert node.styles.background == Color(0, 0, 255)
+    # TODO: On Tuesday - writing the tests for prioritising user CSS above widget CSS.
+
+
 @pytest.mark.parametrize(
     "css_value,expectation,expected_color",
     [

From 972aeece649bc2f1eaa74378c1c43e06b3ffad74 Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenb900@gmail.com>
Date: Tue, 28 Jun 2022 17:26:18 +0100
Subject: [PATCH 4/7] Add Specificity5 for user defined CSS

---
 sandbox/darren/just_a_box.css |  5 -----
 sandbox/darren/just_a_box.py  | 21 +++++++++++++++++++--
 src/textual/css/model.py      |  1 +
 src/textual/css/styles.py     | 18 +++++++++++++-----
 src/textual/css/stylesheet.py | 25 +++++++++++++++++++++----
 src/textual/css/types.py      |  2 ++
 src/textual/widget.py         |  8 ++++----
 tests/css/test_stylesheet.py  | 15 +++++++++------
 8 files changed, 69 insertions(+), 26 deletions(-)

diff --git a/sandbox/darren/just_a_box.css b/sandbox/darren/just_a_box.css
index 1965ecb95..765fd5651 100644
--- a/sandbox/darren/just_a_box.css
+++ b/sandbox/darren/just_a_box.css
@@ -1,8 +1,3 @@
-Screen {
-    layout: dock;
-    height: 100%;
-}
-
 #box {
     height: 50%;
     width: 50%;
diff --git a/sandbox/darren/just_a_box.py b/sandbox/darren/just_a_box.py
index 2541c7b2b..0750afc43 100644
--- a/sandbox/darren/just_a_box.py
+++ b/sandbox/darren/just_a_box.py
@@ -1,10 +1,27 @@
+from __future__ import annotations
+
+from rich.console import RenderableType
+from rich.panel import Panel
+
 from textual.app import App, ComposeResult
-from textual.widgets import Static
+from textual.widget import Widget
+
+
+class Box(Widget):
+    CSS = "#box {background: blue;}"
+
+    def __init__(
+        self, id: str | None = None, classes: str | None = None, *children: Widget
+    ):
+        super().__init__(*children, id=id, classes=classes)
+
+    def render(self) -> RenderableType:
+        return Panel("Box")
 
 
 class JustABox(App):
     def compose(self) -> ComposeResult:
-        yield Static("Hello, World!", id="box")
+        yield Box(id="box")
 
 
 if __name__ == "__main__":
diff --git a/src/textual/css/model.py b/src/textual/css/model.py
index 89623ac95..bf4e9e7c8 100644
--- a/src/textual/css/model.py
+++ b/src/textual/css/model.py
@@ -156,6 +156,7 @@ class RuleSet:
     styles: Styles = field(default_factory=Styles)
     errors: list[tuple[Token, str]] = field(default_factory=list)
     classes: set[str] = field(default_factory=set)
+    is_widget_rule_set: bool = False
 
     @classmethod
     def _selector_to_css(cls, selectors: list[Selector]) -> str:
diff --git a/src/textual/css/styles.py b/src/textual/css/styles.py
index 30a2f2234..4530bacd2 100644
--- a/src/textual/css/styles.py
+++ b/src/textual/css/styles.py
@@ -56,6 +56,7 @@ from .types import (
     AlignVertical,
     Visibility,
     ScrollbarGutter,
+    Specificity5,
 )
 
 if sys.version_info >= (3, 8):
@@ -511,20 +512,27 @@ class Styles(StylesBase):
         self._rules.update(rules)
 
     def extract_rules(
-        self, specificity: Specificity3
-    ) -> list[tuple[str, Specificity4, Any]]:
-        """Extract rules from Styles object, and apply !important css specificity.
+        self,
+        specificity: Specificity3,
+        is_widget_rule: bool = False,
+    ) -> list[tuple[str, Specificity5, Any]]:
+        """Extract rules from Styles object, and apply !important css specificity as
+        well as higher specificity of user CSS vs widget CSS.
 
         Args:
             specificity (Specificity3): A node specificity.
 
         Returns:
-            list[tuple[str, Specificity4, Any]]]: A list containing a tuple of <RULE NAME>, <SPECIFICITY> <RULE VALUE>.
+            list[tuple[str, Specificity5, Any]]]: A list containing a tuple of <RULE NAME>, <SPECIFICITY> <RULE VALUE>.
         """
         is_important = self.important.__contains__
 
         rules = [
-            (rule_name, (int(is_important(rule_name)), *specificity), rule_value)
+            (
+                rule_name,
+                (int(not is_widget_rule), int(is_important(rule_name)), *specificity),
+                rule_value,
+            )
             for rule_name, rule_value in self._rules.items()
         ]
 
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index b627a6e8f..bc2f6e61c 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -122,6 +122,8 @@ class Stylesheet:
         self._rules: list[RuleSet] = []
         self.variables = variables or {}
         self.source: dict[str, str] = {}
+        # Records which of the source keys represent CSS defined at the widget level
+        self._widget_css_paths: set[str] = set()
         self._require_parse = False
 
     def __rich_repr__(self) -> rich.repr.Result:
@@ -147,6 +149,7 @@ class Stylesheet:
         """
         stylesheet = Stylesheet(variables=self.variables.copy())
         stylesheet.source = self.source.copy()
+        stylesheet._widget_css_paths = self._widget_css_paths.copy()
         return stylesheet
 
     def set_variables(self, variables: dict[str, str]) -> None:
@@ -160,7 +163,6 @@ class Stylesheet:
     def _parse_rules(self, css: str, path: str | PurePath) -> list[RuleSet]:
         """Parse CSS and return rules.
 
-
         Args:
             css (str): String containing Textual CSS.
             path (str | PurePath): Path to CSS or unique identifier
@@ -177,6 +179,11 @@ class Stylesheet:
             raise
         except Exception as error:
             raise StylesheetError(f"failed to parse css; {error}")
+
+        if path in self._widget_css_paths:
+            for rule in rules:
+                rule.is_widget_rule_set = True
+
         return rules
 
     def read(self, filename: str | PurePath) -> None:
@@ -199,13 +206,17 @@ class Stylesheet:
         self.source[str(path)] = css
         self._require_parse = True
 
-    def add_source(self, css: str, path: str | PurePath | None = None) -> None:
+    def add_source(
+        self, css: str, path: str | PurePath | None = None, is_widget_css: bool = False
+    ) -> None:
         """Parse CSS from a string.
 
         Args:
             css (str): String with CSS source.
             path (str | PurePath, optional): The path of the source if a file, or some other identifier.
                 Defaults to None.
+            is_widget_css (bool): True if the CSS is defined in the Widget, False if the CSS is defined
+                in a user stylesheet.
 
         Raises:
             StylesheetError: If the CSS could not be read.
@@ -220,6 +231,11 @@ class Stylesheet:
             # Path already in source, and CSS is identical
             return
 
+        # Record any CSS defined at the widget level for
+        # different specificity treatment from user CSS.
+        if is_widget_css:
+            self._widget_css_paths.add(path)
+
         self.source[path] = css
         self._require_parse = True
 
@@ -286,9 +302,10 @@ class Stylesheet:
 
         # Collect the rules defined in the stylesheet
         for rule in reversed(self.rules):
-            for specificity in _check_rule(rule, node):
+            is_widget_rule = rule.is_widget_rule_set
+            for base_specificity in _check_rule(rule, node):
                 for key, rule_specificity, value in rule.styles.extract_rules(
-                    specificity
+                    base_specificity, is_widget_rule
                 ):
                     rule_attributes[key].append((rule_specificity, value))
 
diff --git a/src/textual/css/types.py b/src/textual/css/types.py
index e7fd749b2..1463bf6fa 100644
--- a/src/textual/css/types.py
+++ b/src/textual/css/types.py
@@ -37,5 +37,7 @@ ScrollbarGutter = Literal["auto", "stable"]
 BoxSizing = Literal["border-box", "content-box"]
 Overflow = Literal["scroll", "hidden", "auto"]
 EdgeStyle = Tuple[EdgeType, Color]
+
 Specificity3 = Tuple[int, int, int]
 Specificity4 = Tuple[int, int, int, int]
+Specificity5 = Tuple[int, int, int, int, int]
diff --git a/src/textual/widget.py b/src/textual/widget.py
index 2100f70fd..11d79780c 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -74,12 +74,12 @@ class Widget(DOMNode):
     CSS = """
     Widget{
         scrollbar-background: $panel-darken-2;
-        scrollbar-background-hover: $panel-darken-3;        
+        scrollbar-background-hover: $panel-darken-3;
         scrollbar-color: $system;
-        scrollbar-color-active: $secondary-darken-1;                
+        scrollbar-color-active: $secondary-darken-1;
         scrollbar-size-vertical: 2;
         scrollbar-size-horizontal: 1;
-        
+
     }
     """
 
@@ -194,7 +194,7 @@ class Widget(DOMNode):
         """
         # Parse the Widget's CSS
         for path, css in self.css:
-            self.app.stylesheet.add_source(css, path=path)
+            self.app.stylesheet.add_source(css, path=path, is_widget_css=True)
 
     def get_box_model(
         self, container: Size, viewport: Size, fraction_unit: Fraction
diff --git a/tests/css/test_stylesheet.py b/tests/css/test_stylesheet.py
index 1727b2911..fd98e8904 100644
--- a/tests/css/test_stylesheet.py
+++ b/tests/css/test_stylesheet.py
@@ -104,22 +104,25 @@ def test_stylesheet_apply_empty_rulesets():
     stylesheet.apply(node)
 
 
-@pytest.mark.xfail(reason="wip")
 def test_stylesheet_apply_user_css_over_widget_css():
-    user_css = ".a {color: red;}"
+    user_css = ".a {color: red; tint: yellow;}"
 
     class MyWidget(Widget):
-        CSS = ".a {color: blue;}"
+        CSS = ".a {color: blue; background: lime;}"
 
     node = MyWidget()
     node.add_class("a")
 
-    print(node.styles.color)
     stylesheet = _make_stylesheet(user_css)
+    stylesheet.add_source(MyWidget.CSS, "widget.py:MyWidget", is_widget_css=True)
     stylesheet.apply(node)
 
-    assert node.styles.background == Color(0, 0, 255)
-    # TODO: On Tuesday - writing the tests for prioritising user CSS above widget CSS.
+    # The node is red because user CSS overrides Widget.CSS
+    assert node.styles.color == Color(255, 0, 0)
+    # The background colour defined in the Widget still applies, since user CSS doesn't override it
+    assert node.styles.background == Color(0, 255, 0)
+    # As expected, the tint colour is yellow, since there's no competition between user or widget CSS
+    assert node.styles.tint == Color(255, 255, 0)
 
 
 @pytest.mark.parametrize(

From 8617cbdc70cb49e7d54936a13bd362c9bc93a362 Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenb900@gmail.com>
Date: Tue, 28 Jun 2022 18:39:39 +0100
Subject: [PATCH 5/7] Update test over user css over widget css to show
 important widget css can be overridden by users too

---
 sandbox/darren/just_a_box.css | 2 +-
 tests/css/test_stylesheet.py  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/sandbox/darren/just_a_box.css b/sandbox/darren/just_a_box.css
index 765fd5651..9182f42c7 100644
--- a/sandbox/darren/just_a_box.css
+++ b/sandbox/darren/just_a_box.css
@@ -2,5 +2,5 @@
     height: 50%;
     width: 50%;
     align: center middle;
-    background: green;
+    background: blue;
 }
diff --git a/tests/css/test_stylesheet.py b/tests/css/test_stylesheet.py
index fd98e8904..b489298e6 100644
--- a/tests/css/test_stylesheet.py
+++ b/tests/css/test_stylesheet.py
@@ -108,7 +108,7 @@ def test_stylesheet_apply_user_css_over_widget_css():
     user_css = ".a {color: red; tint: yellow;}"
 
     class MyWidget(Widget):
-        CSS = ".a {color: blue; background: lime;}"
+        CSS = ".a {color: blue !important; background: lime;}"
 
     node = MyWidget()
     node.add_class("a")

From c00de10262cc70d1300e1a15f736ea64bb3d3fd8 Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenb900@gmail.com>
Date: Tue, 28 Jun 2022 18:52:47 +0100
Subject: [PATCH 6/7] Use more efficient bool to int conversion

---
 sandbox/darren/just_a_box.css | 2 +-
 src/textual/css/styles.py     | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/sandbox/darren/just_a_box.css b/sandbox/darren/just_a_box.css
index 9182f42c7..765fd5651 100644
--- a/sandbox/darren/just_a_box.css
+++ b/sandbox/darren/just_a_box.css
@@ -2,5 +2,5 @@
     height: 50%;
     width: 50%;
     align: center middle;
-    background: blue;
+    background: green;
 }
diff --git a/src/textual/css/styles.py b/src/textual/css/styles.py
index 4530bacd2..6a8a8b6e4 100644
--- a/src/textual/css/styles.py
+++ b/src/textual/css/styles.py
@@ -530,7 +530,11 @@ class Styles(StylesBase):
         rules = [
             (
                 rule_name,
-                (int(not is_widget_rule), int(is_important(rule_name)), *specificity),
+                (
+                    0 if is_widget_rule else 1,
+                    1 if is_important(rule_name) else 0,
+                    *specificity,
+                ),
                 rule_value,
             )
             for rule_name, rule_value in self._rules.items()

From 908e2e940ac19f3bde1896bd6cde7b9eeda0fcf8 Mon Sep 17 00:00:00 2001
From: Darren Burns <darrenb900@gmail.com>
Date: Wed, 29 Jun 2022 13:30:21 +0100
Subject: [PATCH 7/7] Feedback from code review

---
 src/textual/css/model.py      |  2 +-
 src/textual/css/parse.py      | 19 +++++++---
 src/textual/css/styles.py     |  6 ++--
 src/textual/css/stylesheet.py | 68 +++++++++++++++++++++--------------
 src/textual/widget.py         |  2 +-
 tests/css/test_stylesheet.py  | 28 +++++++--------
 6 files changed, 75 insertions(+), 50 deletions(-)

diff --git a/src/textual/css/model.py b/src/textual/css/model.py
index bf4e9e7c8..d5d2eb726 100644
--- a/src/textual/css/model.py
+++ b/src/textual/css/model.py
@@ -156,7 +156,7 @@ class RuleSet:
     styles: Styles = field(default_factory=Styles)
     errors: list[tuple[Token, str]] = field(default_factory=list)
     classes: set[str] = field(default_factory=set)
-    is_widget_rule_set: bool = False
+    is_default_rules: bool = False
 
     @classmethod
     def _selector_to_css(cls, selectors: list[Selector]) -> str:
diff --git a/src/textual/css/parse.py b/src/textual/css/parse.py
index 9052c3b1d..6e3ddb4cd 100644
--- a/src/textual/css/parse.py
+++ b/src/textual/css/parse.py
@@ -80,7 +80,9 @@ def parse_selectors(css_selectors: str) -> tuple[SelectorSet, ...]:
     return selector_set
 
 
-def parse_rule_set(tokens: Iterator[Token], token: Token) -> Iterable[RuleSet]:
+def parse_rule_set(
+    tokens: Iterator[Token], token: Token, is_default_rules: bool = False
+) -> Iterable[RuleSet]:
     get_selector = SELECTOR_MAP.get
     combinator: CombinatorType | None = CombinatorType.DESCENDENT
     selectors: list[Selector] = []
@@ -149,7 +151,10 @@ def parse_rule_set(tokens: Iterator[Token], token: Token) -> Iterable[RuleSet]:
             errors.append((error.token, error.message))
 
     rule_set = RuleSet(
-        list(SelectorSet.from_selectors(rule_selectors)), styles_builder.styles, errors
+        list(SelectorSet.from_selectors(rule_selectors)),
+        styles_builder.styles,
+        errors,
+        is_default_rules=is_default_rules,
     )
     rule_set._post_parse()
     yield rule_set
@@ -307,7 +312,10 @@ def substitute_references(
 
 
 def parse(
-    css: str, path: str | PurePath, variables: dict[str, str] | None = None
+    css: str,
+    path: str | PurePath,
+    variables: dict[str, str] | None = None,
+    is_default_rules: bool = False,
 ) -> Iterable[RuleSet]:
     """Parse CSS by tokenizing it, performing variable substitution,
     and generating rule sets from it.
@@ -315,6 +323,9 @@ def parse(
     Args:
         css (str): The input CSS
         path (str): Path to the CSS
+        variables (dict[str, str]): Substitution variables to substitute tokens for.
+        is_default_rules (bool): True if the rules we're extracting are
+            default (i.e. in Widget.CSS) rules. False if they're from user defined CSS.
     """
     variable_tokens = tokenize_values(variables or {})
     tokens = iter(substitute_references(tokenize(css, path), variable_tokens))
@@ -323,7 +334,7 @@ def parse(
         if token is None:
             break
         if token.name.startswith("selector_start"):
-            yield from parse_rule_set(tokens, token)
+            yield from parse_rule_set(tokens, token, is_default_rules=is_default_rules)
 
 
 if __name__ == "__main__":
diff --git a/src/textual/css/styles.py b/src/textual/css/styles.py
index 6a8a8b6e4..d2e0a042d 100644
--- a/src/textual/css/styles.py
+++ b/src/textual/css/styles.py
@@ -514,13 +514,15 @@ class Styles(StylesBase):
     def extract_rules(
         self,
         specificity: Specificity3,
-        is_widget_rule: bool = False,
+        is_default_rules: bool = False,
     ) -> list[tuple[str, Specificity5, Any]]:
         """Extract rules from Styles object, and apply !important css specificity as
         well as higher specificity of user CSS vs widget CSS.
 
         Args:
             specificity (Specificity3): A node specificity.
+            is_default_rules (bool): True if the rules we're extracting are
+                default (i.e. in Widget.CSS) rules. False if they're from user defined CSS.
 
         Returns:
             list[tuple[str, Specificity5, Any]]]: A list containing a tuple of <RULE NAME>, <SPECIFICITY> <RULE VALUE>.
@@ -531,7 +533,7 @@ class Styles(StylesBase):
             (
                 rule_name,
                 (
-                    0 if is_widget_rule else 1,
+                    0 if is_default_rules else 1,
                     1 if is_important(rule_name) else 0,
                     *specificity,
                 ),
diff --git a/src/textual/css/stylesheet.py b/src/textual/css/stylesheet.py
index bc2f6e61c..02a641168 100644
--- a/src/textual/css/stylesheet.py
+++ b/src/textual/css/stylesheet.py
@@ -4,7 +4,7 @@ import os
 from collections import defaultdict
 from operator import itemgetter
 from pathlib import Path, PurePath
-from typing import cast, Iterable
+from typing import cast, Iterable, NamedTuple
 
 import rich.repr
 from rich.console import RenderableType, RenderResult, Console, ConsoleOptions
@@ -116,14 +116,26 @@ class StylesheetErrors:
         )
 
 
+class CssSource(NamedTuple):
+    """Contains the CSS content and whether or not the CSS comes from user defined stylesheets
+    vs widget-level stylesheets.
+
+    Args:
+        content (str): The CSS as a string.
+        is_defaults (bool): True if the CSS is default (i.e. that defined at the widget level).
+            False if it's user CSS (which will override the defaults).
+    """
+
+    content: str
+    is_defaults: bool
+
+
 @rich.repr.auto(angular=True)
 class Stylesheet:
     def __init__(self, *, variables: dict[str, str] | None = None) -> None:
         self._rules: list[RuleSet] = []
         self.variables = variables or {}
-        self.source: dict[str, str] = {}
-        # Records which of the source keys represent CSS defined at the widget level
-        self._widget_css_paths: set[str] = set()
+        self.source: dict[str, CssSource] = {}
         self._require_parse = False
 
     def __rich_repr__(self) -> rich.repr.Result:
@@ -149,7 +161,6 @@ class Stylesheet:
         """
         stylesheet = Stylesheet(variables=self.variables.copy())
         stylesheet.source = self.source.copy()
-        stylesheet._widget_css_paths = self._widget_css_paths.copy()
         return stylesheet
 
     def set_variables(self, variables: dict[str, str]) -> None:
@@ -160,12 +171,17 @@ class Stylesheet:
         """
         self.variables = variables
 
-    def _parse_rules(self, css: str, path: str | PurePath) -> list[RuleSet]:
+    def _parse_rules(
+        self, css: str, path: str | PurePath, is_default_rules: bool = False
+    ) -> list[RuleSet]:
         """Parse CSS and return rules.
 
         Args:
+            is_default_rules:
             css (str): String containing Textual CSS.
             path (str | PurePath): Path to CSS or unique identifier
+            is_default_rules (bool): True if the rules we're extracting are
+                default (i.e. in Widget.CSS) rules. False if they're from user defined CSS.
 
         Raises:
             StylesheetError: If the CSS is invalid.
@@ -174,16 +190,19 @@ class Stylesheet:
             list[RuleSet]: List of RuleSets.
         """
         try:
-            rules = list(parse(css, path, variables=self.variables))
+            rules = list(
+                parse(
+                    css,
+                    path,
+                    variables=self.variables,
+                    is_default_rules=is_default_rules,
+                )
+            )
         except TokenizeError:
             raise
         except Exception as error:
             raise StylesheetError(f"failed to parse css; {error}")
 
-        if path in self._widget_css_paths:
-            for rule in rules:
-                rule.is_widget_rule_set = True
-
         return rules
 
     def read(self, filename: str | PurePath) -> None:
@@ -203,11 +222,11 @@ class Stylesheet:
             path = os.path.abspath(filename)
         except Exception as error:
             raise StylesheetError(f"unable to read {filename!r}; {error}")
-        self.source[str(path)] = css
+        self.source[str(path)] = CssSource(content=css, is_defaults=False)
         self._require_parse = True
 
     def add_source(
-        self, css: str, path: str | PurePath | None = None, is_widget_css: bool = False
+        self, css: str, path: str | PurePath | None = None, is_default_css: bool = False
     ) -> None:
         """Parse CSS from a string.
 
@@ -215,7 +234,7 @@ class Stylesheet:
             css (str): String with CSS source.
             path (str | PurePath, optional): The path of the source if a file, or some other identifier.
                 Defaults to None.
-            is_widget_css (bool): True if the CSS is defined in the Widget, False if the CSS is defined
+            is_default_css (bool): True if the CSS is defined in the Widget, False if the CSS is defined
                 in a user stylesheet.
 
         Raises:
@@ -227,16 +246,11 @@ class Stylesheet:
             path = str(hash(css))
         elif isinstance(path, PurePath):
             path = str(css)
-        if path in self.source and self.source[path] == css:
+        if path in self.source and self.source[path].content == css:
             # Path already in source, and CSS is identical
             return
 
-        # Record any CSS defined at the widget level for
-        # different specificity treatment from user CSS.
-        if is_widget_css:
-            self._widget_css_paths.add(path)
-
-        self.source[path] = css
+        self.source[path] = CssSource(content=css, is_defaults=is_default_css)
         self._require_parse = True
 
     def parse(self) -> None:
@@ -247,8 +261,8 @@ class Stylesheet:
         """
         rules: list[RuleSet] = []
         add_rules = rules.extend
-        for path, css in self.source.items():
-            css_rules = self._parse_rules(css, path)
+        for path, (css, is_default_rules) in self.source.items():
+            css_rules = self._parse_rules(css, path, is_default_rules=is_default_rules)
             if any(rule.errors for rule in css_rules):
                 error_renderable = StylesheetErrors(css_rules)
                 raise StylesheetParseError(error_renderable)
@@ -266,8 +280,8 @@ class Stylesheet:
         """
         # Do this in a fresh Stylesheet so if there are errors we don't break self.
         stylesheet = Stylesheet(variables=self.variables)
-        for path, css in self.source.items():
-            stylesheet.add_source(css, path)
+        for path, (css, is_defaults) in self.source.items():
+            stylesheet.add_source(css, path, is_default_css=is_defaults)
         stylesheet.parse()
         self._rules = stylesheet.rules
         self.source = stylesheet.source
@@ -302,10 +316,10 @@ class Stylesheet:
 
         # Collect the rules defined in the stylesheet
         for rule in reversed(self.rules):
-            is_widget_rule = rule.is_widget_rule_set
+            is_default_rules = rule.is_default_rules
             for base_specificity in _check_rule(rule, node):
                 for key, rule_specificity, value in rule.styles.extract_rules(
-                    base_specificity, is_widget_rule
+                    base_specificity, is_default_rules
                 ):
                     rule_attributes[key].append((rule_specificity, value))
 
diff --git a/src/textual/widget.py b/src/textual/widget.py
index 11d79780c..91c2ae9bc 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -194,7 +194,7 @@ class Widget(DOMNode):
         """
         # Parse the Widget's CSS
         for path, css in self.css:
-            self.app.stylesheet.add_source(css, path=path, is_widget_css=True)
+            self.app.stylesheet.add_source(css, path=path, is_default_css=True)
 
     def get_box_model(
         self, container: Size, viewport: Size, fraction_unit: Fraction
diff --git a/tests/css/test_stylesheet.py b/tests/css/test_stylesheet.py
index b489298e6..14b912f00 100644
--- a/tests/css/test_stylesheet.py
+++ b/tests/css/test_stylesheet.py
@@ -3,20 +3,18 @@ from typing import Any
 
 import pytest
 
-from tests.utilities.test_app import AppTest
-from textual.app import App, ComposeResult
 from textual.color import Color
 from textual.css._help_renderables import HelpText
-from textual.css.stylesheet import Stylesheet, StylesheetParseError
+from textual.css.stylesheet import Stylesheet, StylesheetParseError, CssSource
 from textual.css.tokenizer import TokenizeError
 from textual.dom import DOMNode
 from textual.geometry import Spacing
 from textual.widget import Widget
 
 
-def _make_stylesheet(css: str) -> Stylesheet:
+def _make_user_stylesheet(css: str) -> Stylesheet:
     stylesheet = Stylesheet()
-    stylesheet.source["test.css"] = css
+    stylesheet.source["test.css"] = CssSource(css, is_defaults=False)
     stylesheet.parse()
     return stylesheet
 
@@ -24,7 +22,7 @@ def _make_stylesheet(css: str) -> Stylesheet:
 def test_stylesheet_apply_highest_specificity_wins():
     """#ids have higher specificity than .classes"""
     css = "#id {color: red;} .class {color: blue;}"
-    stylesheet = _make_stylesheet(css)
+    stylesheet = _make_user_stylesheet(css)
     node = DOMNode(classes="class", id="id")
     stylesheet.apply(node)
 
@@ -33,7 +31,7 @@ def test_stylesheet_apply_highest_specificity_wins():
 
 def test_stylesheet_apply_doesnt_override_defaults():
     css = "#id {color: red;}"
-    stylesheet = _make_stylesheet(css)
+    stylesheet = _make_user_stylesheet(css)
     node = DOMNode(id="id")
     stylesheet.apply(node)
 
@@ -45,7 +43,7 @@ def test_stylesheet_apply_highest_specificity_wins_multiple_classes():
     """When we use two selectors containing only classes, then the selector
     `.b.c` has greater specificity than the selector `.a`"""
     css = ".b.c {background: blue;} .a {background: red; color: lime;}"
-    stylesheet = _make_stylesheet(css)
+    stylesheet = _make_user_stylesheet(css)
     node = DOMNode(classes="a b c")
     stylesheet.apply(node)
 
@@ -58,7 +56,7 @@ def test_stylesheet_many_classes_dont_overrule_id():
     a selector containing multiple classes cannot take priority over even a
     single class."""
     css = "#id {color: red;} .a.b.c.d {color: blue;}"
-    stylesheet = _make_stylesheet(css)
+    stylesheet = _make_user_stylesheet(css)
     node = DOMNode(classes="a b c d", id="id")
     stylesheet.apply(node)
 
@@ -67,7 +65,7 @@ def test_stylesheet_many_classes_dont_overrule_id():
 
 def test_stylesheet_last_rule_wins_when_same_rule_twice_in_one_ruleset():
     css = "#id {color: red; color: blue;}"
-    stylesheet = _make_stylesheet(css)
+    stylesheet = _make_user_stylesheet(css)
     node = DOMNode(id="id")
     stylesheet.apply(node)
 
@@ -76,7 +74,7 @@ def test_stylesheet_last_rule_wins_when_same_rule_twice_in_one_ruleset():
 
 def test_stylesheet_rulesets_merged_for_duplicate_selectors():
     css = "#id {color: red; background: lime;} #id {color:blue;}"
-    stylesheet = _make_stylesheet(css)
+    stylesheet = _make_user_stylesheet(css)
     node = DOMNode(id="id")
     stylesheet.apply(node)
 
@@ -88,7 +86,7 @@ def test_stylesheet_apply_takes_final_rule_in_specificity_clash():
     """.a and .b both contain background and have same specificity, so .b wins
     since it was declared last - the background should be blue."""
     css = ".a {background: red; color: lime;} .b {background: blue;}"
-    stylesheet = _make_stylesheet(css)
+    stylesheet = _make_user_stylesheet(css)
     node = DOMNode(classes="a b", id="c")
     stylesheet.apply(node)
 
@@ -99,7 +97,7 @@ def test_stylesheet_apply_takes_final_rule_in_specificity_clash():
 def test_stylesheet_apply_empty_rulesets():
     """Ensure that we don't crash when working with empty rulesets"""
     css = ".a {} .b {}"
-    stylesheet = _make_stylesheet(css)
+    stylesheet = _make_user_stylesheet(css)
     node = DOMNode(classes="a b")
     stylesheet.apply(node)
 
@@ -113,8 +111,8 @@ def test_stylesheet_apply_user_css_over_widget_css():
     node = MyWidget()
     node.add_class("a")
 
-    stylesheet = _make_stylesheet(user_css)
-    stylesheet.add_source(MyWidget.CSS, "widget.py:MyWidget", is_widget_css=True)
+    stylesheet = _make_user_stylesheet(user_css)
+    stylesheet.add_source(MyWidget.CSS, "widget.py:MyWidget", is_default_css=True)
     stylesheet.apply(node)
 
     # The node is red because user CSS overrides Widget.CSS