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
We want to remove GtkBin and GtkContainer as they don't
provide much useful functionality anymore. This requires
us to move get_request_mode and compute_expand down.
See #2681
SEtting a nonzero xalign on frames had no
effect, since we were always using the full
allocation with here, instead of what the label
needs. Found by using testframe for a second.
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.
The border is now drawn on the frame node, not using an internal border
node, so we are no longer able to align the label to vertically overlap
the border. The property no longer performs its original purpose, & nor
is it a useful candidate for giving a new role, so no point keeping it.
https://bugzilla.gnome.org/show_bug.cgi?id=778886
Since setting a clip is mandatory for almost all widgets, we can as well
change the size-allocate signature to include a out_clip parameter, just
like GtkCssGadget did. And since we now always propagate baselines, we
might as well pass that one on to size-allocate.
This way we can also make sure to transform the clip returned from
size-allocate to parent-coordinates, i.e. the same coordinate space
priv->allocation is in.
Turns out that the destination is the last parameter, not the first one.
This fixes the flickering in the first page of the widget-factory when
using the expander on page 2.
The fact that it doesn’t reuse the existing GtkLabel if present is not
immediately obvious to users (or is it just me?), so clarify that the
pre-existing :label-widget, if any, is always removed and replaced.
It does weird clipping that
(a) nobody likes
(b) is hard to support in the new rendering world.
So we take the easy way out.
The actual frame is now drawn by the frame node around the label.
