Added API to insert and remove children

examples/layout_test/README.rst

@@ -0,0 +1,12 @@
+Layout Test
+===========
+
+Test app that demonstrates adding and removing widgets from box.
+
+Quickstart
+~~~~~~~~~~
+
+To run this example:
+
+    $ pip install toga
+    $ python -m layout_test

examples/layout_test/layout_test/__init__.py

@@ -0,0 +1,9 @@
+# Examples of valid version strings
+# __version__ = '1.2.3.dev1'  # Development release 1
+# __version__ = '1.2.3a1'     # Alpha Release 1
+# __version__ = '1.2.3b1'     # Beta Release 1
+# __version__ = '1.2.3rc1'    # RC Release 1
+# __version__ = '1.2.3'       # Final Release
+# __version__ = '1.2.3.post1' # Post Release 1
+
+__version__ = '0.0.1'

examples/layout_test/layout_test/__main__.py

@@ -0,0 +1,4 @@
+from layout_test.app import main
+
+if __name__ == '__main__':
+    main().main_loop()

examples/layout_test/layout_test/app.py

@@ -0,0 +1,119 @@
+import toga
+from toga.style import Pack
+from toga.constants import ROW, COLUMN, CENTER
+
+
+class ExampleBoxApp(toga.App):
+
+    def startup(self):
+
+        self.button_add = toga.Button(
+            label='Add image',
+            style=Pack(padding=10, width=120),
+            on_press=self.add_image,
+        )
+
+        self.button_remove = toga.Button(
+            label='Remove image',
+            style=Pack(padding=10, width=120),
+            on_press=self.remove_image,
+            enabled=False,
+        )
+
+        self.button_insert = toga.Button(
+            label='Insert image',
+            style=Pack(padding=10, width=120),
+            on_press=self.insert_image,
+        )
+
+        self.button_reparent = toga.Button(
+            label='Reparent image',
+            style=Pack(padding=10, width=120),
+            on_press=self.reparent_image,
+            enabled=False,
+        )
+
+        self.button_add_to_scroll = toga.Button(
+            label='Add new label',
+            style=Pack(padding=10, width=120),
+            on_press=self.add_label,
+        )
+
+        self.scroll_box = toga.Box(children=[], style=Pack(direction=COLUMN, padding=10, flex=1))
+        self.scroll_view = toga.ScrollContainer(content=self.scroll_box, style=Pack(width=120))
+
+        icon = toga.Icon('')
+        self.image_view = toga.ImageView(icon, style=Pack(padding=10, width=60, height=60))
+
+        # this tests addind children during init, before we have an implementaiton
+        self.button_box = toga.Box(
+            children=[
+                self.button_add,
+                self.button_insert,
+                self.button_reparent,
+                self.button_remove,
+                self.button_add_to_scroll,
+            ],
+            style=Pack(direction=COLUMN),
+        )
+
+        self.box = toga.Box(
+            children=[self.button_box, self.scroll_view],
+            style=Pack(direction=ROW, padding=10, alignment=CENTER, flex=1)
+        )
+
+        # add a couple of labels to get us started
+        # this tests adding children when we already have an impl but no window or app
+        for i in range(3):
+            self.add_label()
+
+        self.main_window = toga.MainWindow()
+        self.main_window.content = self.box
+        self.main_window.show()
+
+    def add_image(self, sender):
+        self.scroll_box.add(self.image_view)
+
+        self.button_reparent.enabled = True
+        self.button_remove.enabled = True
+        self.button_add.enabled = False
+        self.button_insert.enabled = False
+
+    def insert_image(self, sender):
+        self.scroll_box.insert(1, self.image_view)
+
+        self.button_reparent.enabled = True
+        self.button_remove.enabled = True
+        self.button_add.enabled = False
+        self.button_insert.enabled = False
+
+    def remove_image(self, sender):
+        self.image_view.parent.remove(self.image_view)
+
+        self.button_reparent.enabled = False
+        self.button_remove.enabled = False
+        self.button_add.enabled = True
+        self.button_insert.enabled = True
+
+    def reparent_image(self, sender):
+        if self.image_view.parent is self.button_box:
+            self.scroll_box.insert(0, self.image_view)
+        elif self.image_view.parent is self.scroll_box:
+            self.button_box.add(self.image_view)
+
+    def add_label(self, sender=None):
+        # this tests adding children when we already have an impl, window and app
+        new_label = toga.Label(
+            'Label {}'.format(len(self.scroll_box.children)),
+            style=Pack(padding=2, width=70)
+        )
+        self.scroll_box.add(new_label)
+
+
+def main():
+    return ExampleBoxApp('Layout Test', 'org.beeware.widgets.layout_test')
+
+
+if __name__ == '__main__':
+    app = main()
+    app.main_loop()

examples/layout_test/layout_test/resources/README

@@ -0,0 +1 @@
+Put any icons or images in this directory.

examples/layout_test/pyproject.toml

@@ -0,0 +1,44 @@
+[build-system]
+requires = ["briefcase"]
+
+[tool.briefcase]
+project_name = "Layout Test"
+bundle = "org.beeware"
+version = "0.0.1"
+url = "https://beeware.org"
+license = "BSD license"
+author = 'Tiberius Yak'
+author_email = "tiberius@beeware.org"
+
+[tool.briefcase.app.tayout_test]
+formal_name = "Layout Test"
+description = "A testing app"
+sources = ['tayout_test']
+requires = []
+
+
+[tool.briefcase.app.tayout_test.macOS]
+requires = [
+    'toga-cocoa',
+]
+
+[tool.briefcase.app.tayout_test.linux]
+requires = [
+    'toga-gtk',
+]
+
+[tool.briefcase.app.tayout_test.windows]
+requires = [
+    'toga-winforms',
+]
+
+# Mobile deployments
+[tool.briefcase.app.tayout_test.iOS]
+requires = [
+    'toga-iOS',
+]
+
+[tool.briefcase.app.tayout_test.android]
+requires = [
+    'toga-android',
+]

src/cocoa/toga_cocoa/constraints.py

@@ -35,39 +35,46 @@ def container(self):
 
     @container.setter
     def container(self, value):
-        self._container = value
-        # print("Add constraints for", self.widget, 'in', self.container, self.widget.interface.layout)
-        self.left_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(
-            self.widget.native, NSLayoutAttributeLeft,
-            NSLayoutRelationEqual,
-            self.container.native, NSLayoutAttributeLeft,
-            1.0, 10  # Use a dummy, non-zero value for now
-        )
-        self.container.native.addConstraint(self.left_constraint)
+        if value is None and self.container:
+            self.container.native.removeConstraint(self.width_constraint)
+            self.container.native.removeConstraint(self.height_constraint)
+            self.container.native.removeConstraint(self.left_constraint)
+            self.container.native.removeConstraint(self.top_constraint)
+            self._container = value
+        else:
+            self._container = value
+            # print("Add constraints for", self.widget, 'in', self.container, self.widget.interface.layout)
+            self.left_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(  # NOQA:E501
+                self.widget.native, NSLayoutAttributeLeft,
+                NSLayoutRelationEqual,
+                self.container.native, NSLayoutAttributeLeft,
+                1.0, 10  # Use a dummy, non-zero value for now
+            )
+            self.container.native.addConstraint(self.left_constraint)
 
-        self.top_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(
-            self.widget.native, NSLayoutAttributeTop,
-            NSLayoutRelationEqual,
-            self.container.native, NSLayoutAttributeTop,
-            1.0, 5  # Use a dummy, non-zero value for now
-        )
-        self.container.native.addConstraint(self.top_constraint)
+            self.top_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(  # NOQA:E501
+                self.widget.native, NSLayoutAttributeTop,
+                NSLayoutRelationEqual,
+                self.container.native, NSLayoutAttributeTop,
+                1.0, 5  # Use a dummy, non-zero value for now
+            )
+            self.container.native.addConstraint(self.top_constraint)
 
-        self.width_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(
-            self.widget.native, NSLayoutAttributeRight,
-            NSLayoutRelationEqual,
-            self.widget.native, NSLayoutAttributeLeft,
-            1.0, 50  # Use a dummy, non-zero value for now
-        )
-        self.container.native.addConstraint(self.width_constraint)
+            self.width_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(  # NOQA:E501
+                self.widget.native, NSLayoutAttributeRight,
+                NSLayoutRelationEqual,
+                self.widget.native, NSLayoutAttributeLeft,
+                1.0, 50  # Use a dummy, non-zero value for now
+            )
+            self.container.native.addConstraint(self.width_constraint)
 
-        self.height_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(
-            self.widget.native, NSLayoutAttributeBottom,
-            NSLayoutRelationEqual,
-            self.widget.native, NSLayoutAttributeTop,
-            1.0, 30  # Use a dummy, non-zero value for now
-        )
-        self.container.native.addConstraint(self.height_constraint)
+            self.height_constraint = NSLayoutConstraint.constraintWithItem_attribute_relatedBy_toItem_attribute_multiplier_constant_(  # NOQA:E501
+                self.widget.native, NSLayoutAttributeBottom,
+                NSLayoutRelationEqual,
+                self.widget.native, NSLayoutAttributeTop,
+                1.0, 30  # Use a dummy, non-zero value for now
+            )
+            self.container.native.addConstraint(self.height_constraint)
 
     def update(self, x, y, width, height):
         # print("UPDATE", self.widget, 'in', self.container, 'to', x, y, width, height)

src/cocoa/toga_cocoa/widgets/base.py

@@ -11,6 +11,10 @@ def __init__(self, interface):
         self.native = None
         self.create()
         self.interface.style.reapply()
+        self.set_enabled(self.interface.enabled)
+
+    def create(self):
+        raise NotImplementedError()
 
     def set_app(self, app):
         pass
@@ -24,17 +28,20 @@ def container(self):
 
     @container.setter
     def container(self, container):
-        self._container = container
-        self._container.native.addSubview(self.native)
-        self.constraints.container = container
+
+        if container is None:
+            self.constraints.container = None
+            self._container = None
+            self.native.removeFromSuperview()
+        else:
+            self._container = container
+            self._container.native.addSubview(self.native)
+            self.constraints.container = container
 
         for child in self.interface.children:
             child._impl.container = container
 
         self.rehint()
-        if self.interface.window and self.interface.window._impl.native.isVisible:
-            # refresh window content to reflect added subview
-            self.interface.window.content.refresh()
 
     def set_enabled(self, value):
         self.native.enabled = self.interface.enabled
@@ -64,9 +71,13 @@ def set_background_color(self, color):
     # INTERFACE
 
     def add_child(self, child):
-        # if we don't have a window, we won't have a container
-        if self.interface.window:
-            child.container = self.container or self.interface.window.content._impl
+        child.container = self.container or self
+
+    def insert_child(self, index, child):
+        self.add_child(child)
+
+    def remove_child(self, child):
+        child.container = None
 
     def add_constraints(self):
         self.native.translatesAutoresizingMaskIntoConstraints = False

src/core/setup.py

@@ -31,7 +31,7 @@
     },
     include_package_data=True,
     install_requires=[
-        'travertino>=0.1.0',
+        'travertino>=0.1.3',
         'importlib_metadata;python_version<"3.8"',
     ],
     tests_require=[