fix for min and max with fr unints (#2390)

* fix for min and max with fr unints

* snapshit

* forgot snapshit tests

* fix resolve

* added unit tests

* Windoze fix

tests/snapshot_tests/snapshot_apps/fr_with_min.py

@@ -0,0 +1,50 @@
+from textual.app import App, ComposeResult
+from textual.containers import Horizontal, Vertical, VerticalScroll
+from textual.widgets import Header, Footer, Static
+
+
+class ScreenSplitApp(App[None]):
+    CSS = """
+    Horizontal {
+        width: 1fr;        
+    }
+
+    Vertical {
+        width: 1fr;
+        background: blue;
+        min-width: 20;
+    }
+
+    #scroll1 {
+        width: 1fr;
+        background: $panel;
+    }
+
+    #scroll2 {
+        width: 2fr;
+        background: $panel;
+    }
+
+    Static {
+        width: 1fr;
+        content-align: center middle;
+        background: $boost;
+    }
+
+    """
+
+    def compose(self) -> ComposeResult:
+        yield Header()
+        with Horizontal():
+            yield Vertical()
+            with VerticalScroll(id="scroll1"):
+                for n in range(100):
+                    yield Static(f"This is content number {n}")
+            with VerticalScroll(id="scroll2"):
+                for n in range(100):
+                    yield Static(f"This is content number {n}")
+        yield Footer()
+
+
+if __name__ == "__main__":
+    ScreenSplitApp().run()

tests/snapshot_tests/test_snapshots.py

@@ -319,7 +319,7 @@ def test_demo(snap_compare):
     """Test the demo app (python -m textual)"""
     assert snap_compare(
         Path("../../src/textual/demo.py"),
-        press=["down", "down", "down", "wait:250"],
+        press=["down", "down", "down", "wait:500"],
         terminal_size=(100, 30),
     )
 
@@ -460,3 +460,8 @@ def test_scroll_to_center(snap_compare):
 def test_quickly_change_tabs(snap_compare):
     # https://github.com/Textualize/textual/issues/2229
     assert snap_compare(SNAPSHOT_APPS_DIR / "quickly_change_tabs.py", press=["p"])
+
+
+def test_fr_unit_with_min(snap_compare):
+    # https://github.com/Textualize/textual/issues/2378
+    assert snap_compare(SNAPSHOT_APPS_DIR / "fr_with_min.py")

tests/test_resolve.py

@@ -1,8 +1,11 @@
+from fractions import Fraction
+
 import pytest
 
-from textual._resolve import resolve
+from textual._resolve import resolve, resolve_fraction_unit
 from textual.css.scalar import Scalar
 from textual.geometry import Size
+from textual.widget import Widget
 
 
 def test_resolve_empty():
@@ -56,3 +59,66 @@ def test_resolve(scalars, total, gutter, result):
         )
         == result
     )
+
+
+def test_resolve_fraction_unit():
+    """Test resolving fraction units in combination with minimum widths."""
+    widget1 = Widget()
+    widget2 = Widget()
+    widget3 = Widget()
+
+    widget1.styles.width = "1fr"
+    widget1.styles.min_width = 20
+
+    widget2.styles.width = "2fr"
+    widget2.styles.min_width = 10
+
+    widget3.styles.width = "1fr"
+
+    styles = (widget1.styles, widget2.styles, widget3.styles)
+
+    # Try with width 80.
+    # Fraction unit should one fourth of width
+    assert resolve_fraction_unit(
+        styles,
+        Size(80, 24),
+        Size(80, 24),
+        Fraction(80),
+        resolve_dimension="width",
+    ) == Fraction(20)
+
+    # Try with width 50
+    # First widget is fixed at 20
+    # Remaining three widgets have 30 to play with
+    # Fraction is 10
+    assert resolve_fraction_unit(
+        styles,
+        Size(80, 24),
+        Size(80, 24),
+        Fraction(50),
+        resolve_dimension="width",
+    ) == Fraction(10)
+
+    # Try with width 35
+    # First widget fixed at 20
+    # Fraction is 5
+    assert resolve_fraction_unit(
+        styles,
+        Size(80, 24),
+        Size(80, 24),
+        Fraction(35),
+        resolve_dimension="width",
+    ) == Fraction(5)
+
+    # Try with width 32
+    # First widget fixed at 20
+    # Second widget is fixed at 10
+    # Remaining widget has all the space
+    # Fraction is 2
+    assert resolve_fraction_unit(
+        styles,
+        Size(80, 24),
+        Size(80, 24),
+        Fraction(32),
+        resolve_dimension="width",
+    ) == Fraction(2)