Just like GtkContainer provides a default implementation of
GtkWidgetClass.get_request_mode(), we can do the same inside
GtkLayoutManager.
A default implementation preserves the behavior of existing widgets that
moved, or will move, to a GtkLayoutManager.
If we want to inspect the type of layout properties exposed by a
GtkLayoutManager, we need a way to connect the layout manager type to
the GtkLayoutChild type it creates. In order to do so, we can set the
GtkLayoutChild type on a field of the GtkLayoutManagerClass structure.
Storing the GtkLayoutChild type on the class structure of the layout
manager also allows us to implement a default create_layout_child()
virtual function.
The GtkWidget::parent-set signal was removed in ff6cd8f7.
Instead of removing GtkLayoutChild instances associated to a widget
using notifications when the widget's parent changes, we can have
gtk_widget_unparent() call a method on GtkLayoutManager to remove any
eventual GtkLayoutChild instances associated to the widget.
- Rename GtkLegacyLayout to GtkCustomLayout
- Use for() to iterate over children in GtkBinLayout
- Whitespace fixes for code imported from GtkBox
- Store the GtkLayoutChild instances inside LayoutManager
- Simplify the GtkLayoutManager API by dropping unnecessary arguments
- Fix the ownership model of GtkLayoutManager
Layout managers needs a way to store properties that control the layout
policy of a widget; typically, we used to store these in GtkContainer's
child properties, but since GtkLayoutManager is decoupled from the
actual container widget, we need a separate storage. Additionally, child
properties have their own downsides, like requiring a separate, global
GParamSpecPool storage, and additional lookup API.
GtkLayoutChild is a simple GObject class, which means you can introspect
and document it as you would any other type.
We delegate the size request mode, the measuring, and the allocation of
a widget through a GtkLayoutManager instance, if one has been attached
to the widget; otherwise, we fall back to the widget's own implementation.
A base abstract class for layout manager delegate objects.
Layout managers are associated to a single widget, like event
controllers, and are responsible for measuring and allocating the
children of the widget they are bound to.
