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")