Changed to updated Pack.layout() signature (without node)

changes/244.misc.rst

@@ -0,0 +1 @@
+Node.reresh() has been updated to use Toga 0.5.0's newer signature for style.layout, omitting the node parameter. It is still backwards-compatible with Toga 0.4.8.

src/travertino/declaration.py

@@ -322,6 +322,11 @@ def apply(self, property, value):
             "Style must define an apply method"
         )  # pragma: no cover
 
+    def layout(self, viewport):
+        raise NotImplementedError(
+            "Style must define a layout method"
+        )  # pragma: no cover
+
     ######################################################################
     # Provide a dict-like interface
     ######################################################################

src/travertino/node.py

@@ -1,3 +1,6 @@
+from inspect import signature
+
+
 class Node:
     def __init__(self, style, applicator=None, children=None):
         # Parent needs to be primed before style is (potentially) applied with
@@ -169,10 +172,44 @@ def refresh(self, viewport):
         if self._root:
             self._root.refresh(viewport)
         else:
-            self.style.layout(self, viewport)
             if self.applicator:
+                ######################################################################
+                # 2024-12: Backwards compatibility for Toga <= 0.4.8
+                ######################################################################
+                # (See below)
+                if self._old_layout_args():
+                    self.style.layout(self, viewport)
+                else:
+                    self.style.layout(viewport)
+                ######################################################################
+                # End backwards compatibility
+                ######################################################################
+
                 self.applicator.set_bounds()
 
+    ######################################################################
+    # 2024-12: Backwards compatibility for Toga <= 0.4.8
+    ######################################################################
+
+    # Accommodate the earlier signature of layout(), which included the node as a
+    # parameter. This needs to be called on the *instance* -- to have access to the
+    # style -- but it needs to be cached on the *class*, so all instances have access
+    # to it.
+
+    def _old_layout_args(self):
+        try:
+            return self.__class__._cached_old_layout_args
+        except AttributeError:
+            self.__class__._cached_old_layout_args = (
+                "node" in signature(self.style.layout).parameters
+            )
+
+            return self.__class__._cached_old_layout_args
+
+    ######################################################################
+    # End backwards compatibility
+    ######################################################################
+
     def _set_root(self, node, root):
         # Propagate a root node change through a tree.
         node._root = root

tests/test_node.py

@@ -21,10 +21,16 @@ class IntrinsicSize(BaseIntrinsicSize):
     class Box(BaseBox):
         pass
 
-    def layout(self, root, viewport):
+    def layout(self, viewport):
         # A simple layout scheme that allocates twice the viewport size.
-        root.layout.content_width = viewport.width * 2
-        root.layout.content_height = viewport.height * 2
+        self._applicator.node.layout.content_width = viewport.width * 2
+        self._applicator.node.layout.content_height = viewport.height * 2
+
+
+class OldStyle(Style):
+    # Uses two-argument layout(), as in Toga <= 0.4.8
+    def layout(self, node, viewport):
+        super().layout(viewport)
 
 
 @prep_style_class
@@ -38,10 +44,10 @@ class IntrinsicSize(BaseIntrinsicSize):
     class Box(BaseBox):
         pass
 
-    def layout(self, root, viewport):
+    def layout(self, viewport):
         # A simple layout scheme that allocates twice the viewport size.
-        root.layout.content_width = viewport.width * 2
-        root.layout.content_height = viewport.height * 2
+        self._applicator.node.layout.content_width = viewport.width * 2
+        self._applicator.node.layout.content_height = viewport.height * 2
 
 
 class AttributeTestStyle(BaseStyle):
@@ -130,7 +136,41 @@ def test_create_node():
     assert child3.root == new_node
 
 
-def test_refresh():
+@pytest.mark.parametrize(
+    "StyleClass, cached_value",
+    [
+        (Style, False),
+        (OldStyle, True),
+    ],
+)
+def test_layout_signature_check(StyleClass, cached_value):
+    """After the first call to refresh(), node class should cache args version."""
+
+    class Applicator:
+        def set_bounds(self):
+            pass
+
+    class TestNode(Node):
+        # So we don't change the actual Node class
+        pass
+
+    # Before refresh() is called, the cached value isn't set.
+    assert not hasattr(TestNode, "_cached_old_layout_args")
+
+    # Check again, just to be sure nothing has changed from creating an instance.
+    node = TestNode(style=StyleClass(), applicator=Applicator())
+    assert not hasattr(TestNode, "_cached_old_layout_args")
+
+    # Refresh for the first time.
+    node.refresh(Viewport(width=10, height=20))
+
+    # After refreshing, which signature to use for layout() should be cached on the
+    # class, and thus accessible to both instances.
+    assert TestNode._cached_old_layout_args == cached_value
+
+
+@pytest.mark.parametrize("StyleClass", [Style, OldStyle])
+def test_refresh(StyleClass):
     """The layout can be refreshed, and the applicator invoked"""
 
     # Define an applicator that tracks the node being rendered and its size
@@ -155,7 +195,7 @@ def __init__(self, style, children=None):
             )
 
     # Define a simple 2 level tree of nodes.
-    style = Style()
+    style = StyleClass()
     child1 = TestNode(style=style)
     child2 = TestNode(style=style)
     child3 = TestNode(style=style)