Add windows CSS keyword support and tests

changes/1814.misc.rst

@@ -0,0 +1 @@
+Support for CSS keywords in Windows.

core/tests/style/pack/test_css.py

@@ -449,6 +449,16 @@
             "flex-direction: row; flex: 0.0 0 auto; font-size: 42pt;",
             id="font-size",
         ),
+        pytest.param(
+            Pack(font_size="smaller"),
+            "flex-direction: row; flex: 0.0 0 auto; font-size: smaller;",
+            id="font-size-smaller",
+        ),
+        pytest.param(
+            Pack(font_size="large"),
+            "flex-direction: row; flex: 0.0 0 auto; font-size: large;",
+            id="font-size-large",
+        ),
         pytest.param(
             Pack(font_size=SYSTEM_DEFAULT_FONT_SIZE),
             "flex-direction: row; flex: 0.0 0 auto;",

testbed/tests/test_fonts.py

@@ -1,6 +1,10 @@
 from importlib import import_module
 
 import pytest
+from travertino.constants import (
+    ABSOLUTE_FONT_SIZES,
+    RELATIVE_FONT_SIZES,
+)
 
 import toga
 from toga.fonts import (
@@ -53,7 +57,12 @@ async def test_use_system_font_fallback(
 async def test_font_options(widget: toga.Label, font_probe):
     """Every combination of weight, style and variant can be used on a font."""
     for font_family in SYSTEM_DEFAULT_FONTS:
-        for font_size in [20, SYSTEM_DEFAULT_FONT_SIZE]:
+        for font_size in [
+            20,
+            SYSTEM_DEFAULT_FONT_SIZE,
+            *ABSOLUTE_FONT_SIZES,
+            *RELATIVE_FONT_SIZES,
+        ]:
             for font_weight in FONT_WEIGHTS:
                 for font_style in FONT_STYLES:
                     for font_variant in FONT_VARIANTS:

winforms/src/toga_winforms/fonts.py

@@ -8,6 +8,13 @@
 from System.Drawing.Text import PrivateFontCollection
 from System.IO import FileNotFoundException
 from System.Runtime.InteropServices import ExternalException
+from travertino.constants import (
+    ABSOLUTE_FONT_SIZES,
+    FONT_SIZE_SCALE,
+    RELATIVE_FONT_SIZE_SCALE,
+    RELATIVE_FONT_SIZES,
+    SYSTEM_DEFAULT_FONT_SIZE,
+)
 
 from toga.fonts import (
     _REGISTERED_FONT_CACHE,
@@ -18,7 +25,6 @@
     SANS_SERIF,
     SERIF,
     SYSTEM,
-    SYSTEM_DEFAULT_FONT_SIZE,
 )
 
 _FONT_CACHE = {}
@@ -93,6 +99,18 @@ def __init__(self, interface):
             # Convert font size to Winforms format
             if self.interface.size == SYSTEM_DEFAULT_FONT_SIZE:
                 font_size = DEFAULT_FONT.Size
+            elif (
+                isinstance(self.interface.size, str)
+                and self.interface.size in ABSOLUTE_FONT_SIZES
+            ):
+                font_size = DEFAULT_FONT.Size
+                font_size *= FONT_SIZE_SCALE.get(self.interface.size, 1.0)
+            elif (
+                isinstance(self.interface.size, str)
+                and self.interface.size in RELATIVE_FONT_SIZES
+            ):
+                font_size = getattr(self.interface, "_parent_size", DEFAULT_FONT.Size)
+                font_size *= RELATIVE_FONT_SIZE_SCALE.get(self.interface.size, 1.0)
             else:
                 font_size = self.interface.size
 

winforms/tests_backend/fonts.py

@@ -1,4 +1,9 @@
 from System.Drawing import FontFamily, SystemFonts
+from travertino.constants import (
+    FONT_SIZE_SCALE,
+    RELATIVE_FONT_SIZE_SCALE,
+    RELATIVE_FONT_SIZES,
+)
 
 from toga.fonts import (
     BOLD,
@@ -45,8 +50,15 @@ def font_size(self):
 
     def assert_font_size(self, expected):
         if expected == SYSTEM_DEFAULT_FONT_SIZE:
-            expected = 9
-        assert self.font_size == expected
+            expected = 9.0
+        elif isinstance(expected, str):
+            base_size = 9.0
+            if expected in RELATIVE_FONT_SIZES:
+                parent_size = getattr(self, "_parent_size", base_size)
+                expected = parent_size * RELATIVE_FONT_SIZE_SCALE.get(expected, 1.0)
+            else:
+                expected = base_size * FONT_SIZE_SCALE.get(expected, 1.0)
+        assert abs(self.font.SizeInPoints - expected) < 0.1
 
     def assert_font_family(self, expected):
         assert str(self.font.Name) == {