This is implemented using a new xdg_toplevel `suspended` state, and is
meant for allowing applications to know when they can stop doing
unnecessary work and thus save power.
In the other backends, the `suspended` state is set at the same time as
`minimized` as it's the closest there is to traditional windowing
systems.
It was used by all surfaces to track 'is-mapped', but still part of the
GdkToplevelState, and is now replaced with a separate boolean in the
GdkSurface structure.
It also caused issues when a widget was unmapped, and due to that
unmapped a popover which hid its corresponding surface. When this
surface was hidden, it emitted a state change event, which would then go
back into GTK and queue a resize on popover widget, which would travel
back down to the widget that was originally unmapped, causing confusino
when doing future allocations.
To summarize, one should not hide widgets during allocation, and to
avoid this, make this new is-mapped boolean asynchronous when hiding a
surface, meaning the notification event for the changed mapped state
will be emitted in an idle callback. This avoids the above described
reentry issue.
The plan is to concencrate size computations as part of the frame clock
dispatch, meaning we shouldn't do it synchronously in the present()
function.
Still, in Wayland, and maybe elsewhere, it is done in the present()
function, e.g. when no state change was made, but this will eventually
be changed.
GTK will not up front know how to correctly calculate a size, since it
will not be able to reliably predict the constraints that may exist
where it will be mapped.
Thus, to handle this, calculate the size of the toplevel by having GDK
emitting a signal called 'compute-size' that will contain information
needed for computing a toplevel window size.
This signal may be emitted at any time, e.g. during
gdk_toplevel_present(), or spontaneously if constraints change.
This also drops the max size from the toplevel layout, while moving the
min size from the toplevel layout struct to the struct passed via the
signal,
This needs changes to a test case where we make sure we process
GDK_CONFIGURE etc, which means we also needs to show the window and
process all pending events in the test-focus-chain test case.
With the removal of grabs from the public API, we need a replacement API
to let applications bypass system keyboard shortcuts.
A typical use case for this API is remote desktop or virtual machine
viewers which need to inhibit the default system keyboard shortcuts so
that the remote session or virtual host gets those instead of the local
environment.
Close: https://gitlab.gnome.org/GNOME/gtk/issues/982
