Unparent the child widget before tearing down its
stack page. This is necessary so a11y can still access
the stack page accessible to emit change notification
when it learns that the child is removed.
This requires some cleanup to remove assumptions
about accessibles being widgets in the backend,
and some code to navigate the tree with these
extra objects in between widgets.
The accessibles for stack pages have the role
GTK_ACCESSIBLE_ROLE_TAB_PANEL. This is the first
step towards implementing the tabs patterns
as described in the aria authoring guidelines
for GtkStack.
To build a better world sometimes means having to tear the old one down.
-- Alexander Pierce, "Captain America: The Winter Soldier"
ATK served us well for nearly 20 years, but the world has changed, and
GTK has changed with it. Now ATK is mostly a hindrance towards improving
the accessibility stack:
- it maps to a very specific implementation, AT-SPI, which is Linux and
Unix specific
- it requires implementing the same functionality in three different
layers of the stack: AT-SPI, ATK, and GTK
- only GTK uses it; every other Linux and Unix toolkit and application
talks to AT-SPI directly, including assistive technologies
Sadly, we cannot incrementally port GTK to a new accessibility stack;
since ATK insulates us entirely from the underlying implementation, we
cannot replace it piecemeal. Instead, we're going to remove everything
and then incrementally build on a clean slate:
- add an "accessible" interface, implemented by GTK objects directly,
which describe the accessible role and state changes for every UI
element
- add an "assistive technology context" to proxy a native accessibility
API, and assign it to every widget
- implement the AT context depending on the platform
For more information, see: https://gitlab.gnome.org/GNOME/gtk/-/issues/2833
The stack wasn't updating its visible-child when
the stack pages visible property changes. This
showed up in the inspector, when showing the details
for a list model item.
All widgets cache their render node already. Just allocate the
last_visible_child always at 0/0 and then move its rendernode around
during snapshot.
Fixes#2678
This was only living in gtkcontainer.c for historic
reasons. Move it closer to where it belongs, and
rename it from 'idle' to 'layout', since it is
really about the layout phase of the frame clock,
nowadays.
We need to remove the weak pointer, as the stack switcher can
keep the list model alive beyond the stack. This was observed
to cause crashes:
==16870== Invalid write of size 8
==16870== at 0x5168A4E: g_nullify_pointer (gutils.c:2284)
==16870== by 0x522C500: weak_refs_notify (gobject.c:2791)
==16870== by 0x50FE7BC: g_data_set_internal (gdataset.c:407)
==16870== by 0x50FECA7: g_datalist_id_set_data_full (gdataset.c:670)
==16870== by 0x5227EB4: g_object_real_dispose (gobject.c:1056)
==16870== by 0x522D295: g_object_unref (gobject.c:3309)
==16870== by 0x4AF849F: unset_stack (gtkstackswitcher.c:428)
==16870== by 0x4AF892E: gtk_stack_switcher_dispose (gtkstackswitcher.c:527)
