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.
This will sometimes mean a frame is skipped if a resize was requested
during the update phase of the frame dispatch. Not doing so can cause
trying to allocate a window smaller than the minimum size of the widget.
If compute_size() returns TRUE, the layout will not be propagated to
GTK. This will be used by the X11 backend to queue asynchronous resizes
that shouldn't yet allocate in GTK.
This removes the gdk_surface_set_shadow_width() function and related
vfuncs. The point here is that the shadow width and surface size can now
be communicated to GDK atomically, meaning it's possible to avoid
intermediate stages where the surface size includes the shadow, but
without the shadow width set, or the other way around.
This follows the trail of the Wayland backend in that GdkSurface changes
happen during the layout phase, and that a GDK_CONFIGURE no longer being
used to communicate the size changes of a surface; this now also uses
the layout signal on the GdkSurface.
Reading the comment, it seems to be related being a window manager
decoration utility; this is not something GTK4 aims to handle, just drop
support for this.
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.
