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
After the :can-focus change in the previous commit, widgets
need to set suitable focus and grab_focus implementations
to implement the desired focus behavior.
This commit does that for all widgets.
Replace uses of gtk_css_style_get_value with direct access,
throughout the tree. We don't replace all uses, just those
where we are dealing with a fixed property. Be careful to
handle the currentColor special case for color properties.
This commit introduces GtkPicture, which is supposed to complement
GtkImage.
GtkImage will be adapted to always display an icon, while
GtkPicture displays regular imagery.
