Revive textual backend

changes/2822.bugfix.rst

@@ -0,0 +1 @@
+The Textual backend is now compatible with versions of Textual after v0.63.3.

textual/src/toga_textual/app.py

@@ -51,7 +51,7 @@ def exit(self):
         self.native.exit()
 
     def main_loop(self):
-        self.native.run()
+        self.loop.run_until_complete(self.native.run_async())
 
     def set_icon(self, icon):
         pass

textual/src/toga_textual/widgets/base.py

@@ -36,6 +36,24 @@ def __init__(self, interface):
         self.container = None
         self.create()
 
+        self._pending_children: list[Widget] = list()
+
+    def install(self, parent):
+        """Add widget and any pending children to the native DOM for the app.
+
+        Textual does not allow widgets to be added to the DOM until their parent is
+        added. Therefore, when children are added to an unmounted widget, their
+        mounting is deferred until their parent is mounted.
+        """
+        # Mount widget on to its parent
+        parent.native.mount(self.native)
+
+        # Mount any pending children as native children
+        for child in self._pending_children:
+            child.install(parent=self)
+
+        self._pending_children.clear()
+
     def get_size(self) -> Size:
         return Size(0, 0)
 
@@ -74,7 +92,7 @@ def set_bounds(self, x, y, width, height):
 
         # Positions are more complicated. The (x,y) provided as an argument is
         # in absolute coordinates. The `content_left` ad `content_right` values
-        # of the layout are relative coordianate. Textual doesn't allow specifying
+        # of the layout are relative coordinate. Textual doesn't allow specifying
         # either absolute *or* relative - we can only specify margin values within
         # a row/column box. This means we need to reverse engineer the margins from
         # the computed layout.
@@ -152,13 +170,21 @@ def set_background_color(self, color):
     ######################################################################
 
     def add_child(self, child):
-        self.native.mount(child.native)
+        # A child can only be added to a widget that is already mounted on the app.
+        # So, mounting the child is deferred if the parent is not mounted yet.
+        if self.native.is_attached:
+            self.native.mount(child.native)
+        else:
+            self._pending_children.append(child)
 
     def insert_child(self, index, child):
         pass
 
     def remove_child(self, child):
-        self.native.remove(child.native)
+        try:
+            self._pending_children.remove(child)
+        except ValueError:
+            self.native.remove_children([child.native])
 
     def refresh(self):
         intrinsic = self.interface.intrinsic

textual/src/toga_textual/window.py

@@ -146,6 +146,7 @@ def close(self):
         self.native.dismiss(None)
 
     def set_app(self, app):
+        app.native.mount(self.native)
         app.native.install_screen(self.native, name=self.interface.id)
 
     def show(self):
@@ -160,8 +161,7 @@ def clear_content(self):
 
     def set_content(self, widget):
         self.container.content = widget
-
-        self.native.mount(widget.native)
+        widget.install(parent=self)
 
     ######################################################################
     # Window size