UIBoxLayout ignores widgets with visible=None

Author: eruvanos

CHANGELOG.md

@@ -9,6 +9,7 @@ Arcade [PyPi Release History](https://pypi.org/project/arcade/#history) page.
   - Fix a bug, where the caret of UIInputText was misplaced after resizing the widget
   - Use incremental layout for UIScrollArea to improve performance of changing text
   - Refactored and improved focus handling
+  - UIBoxLayout ignores widgets with `visible=None`
 
 ## 3.3.2
 

arcade/gui/widgets/__init__.py

@@ -127,7 +127,9 @@ class UIWidget(EventDispatcher, ABC):
     """A weak reference to the parent UIManager or UIWidget,
     which does not prevent garbage collection of the parent."""
     rect = Property(LBWH(0, 0, 1, 1))
-    visible = Property(True)
+    visible = Property[bool | None](True)
+    """If True, the widget is visible and will be rendered. If None,
+    the widget should also be skipped by layouts."""
     focused = Property(False)
     focus_mode: FocusMode = FocusMode.NONE
 

arcade/gui/widgets/layout.py

@@ -315,7 +315,9 @@ def _update_size_hints(self):
         self._size_hint_requires_update = False
 
         required_space_between = max(0, len(self.children) - 1) * self._space_between
-        min_child_sizes = [UILayout.min_size_of(child) for child in self.children]
+        min_child_sizes = [
+            UILayout.min_size_of(child) for child in self.children if child.visible is not None
+        ]
 
         if len(self.children) == 0:
             width = 0
@@ -360,10 +362,14 @@ def do_layout(self):
         if not self.children:
             return
 
+        children_to_render = [
+            (child, data) for child, data in self._children if child.visible is not None
+        ]
+
         # main axis
         constraints = [
             _C.from_widget_height(child) if self.vertical else _C.from_widget_width(child)
-            for child, _ in self._children
+            for child, _ in children_to_render
         ]
 
         available_space = (
@@ -374,14 +380,14 @@ def do_layout(self):
         # orthogonal axis
         constraints = [
             _C.from_widget_width(child) if self.vertical else _C.from_widget_height(child)
-            for child, _ in self._children
+            for child, _ in children_to_render
         ]
         orthogonal_sizes = _box_orthogonal_algorithm(
             constraints, self.content_width if self.vertical else self.content_height
         )
 
         for (child, data), main_size, ortho_size in zip(
-            self._children, main_sizes, orthogonal_sizes
+            children_to_render, main_sizes, orthogonal_sizes
         ):
             # apply calculated sizes, condition regarding existing size_hint
             # are already covered in calculation input

tests/unit/gui/test_layouting_boxlayout.py

@@ -128,6 +128,28 @@ def test_do_layout_vertical_space_between(window):
     assert element_2.top == 300
 
 
+def test_do_layout_ignores_child_with_visible_None(window):
+    # add two 100x100 Dummy widgets
+    element_1 = UIDummy()
+    element_1.visible = None
+    element_2 = UIDummy()
+
+    group = UIBoxLayout(vertical=True, children=[element_1, element_2])
+    assert group.size_hint_min == (100, 100)
+    group.rect = LBWH(100, 200, 100, 100)
+
+    group._do_layout()
+
+    # element 1 in initial position
+    assert element_1.bottom == 0
+    assert element_1.left == 0
+
+    # element 2 fills the group
+    assert element_2.top == 300
+    assert element_2.bottom == 200
+    assert element_2.left == 100
+
+
 # Horizontal
 def test_do_layout_horizontal_with_initial_children(window):
     # add two 100x100 Dummy widgets