This is a public API change. Add device/sequence parameters to this
operation, so that window dragging and resizing can stick to one
set of pointing events of them all.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2683>
Move the use count from a separate MetaWaylandBufferRef struct to the
MetaWaylandBuffer class, and remove the former.
The buffer use count is now incremented already in
meta_wayland_surface_commit, since the Wayland protocol defines the
buffer to be in use by the compositor at that point. If the buffer
attachment ends up being dropped again before it is applied to the
surface state (e.g. because another buffer is committed to a
synchronized sub-surface before the parent surface is committed),
the use count is now decremented, and a buffer release event is sent if
the use count drops to 0.
Buffer release events were previously incorrectly not sent under these
circumstances. Test case: Run the weston-subsurfaces demo with the -r1
and/or -t1 command line parameter. Resize the window. Before this
change, weston-subsurfaces would freeze or abort after a few resize
operations, because mutter failed to send release events and the
client ran out of usable buffers.
v2:
* Handle NULL priv->buffer_ref in
meta_wayland_cursor_surface_apply_state.
v3:
* Remove MetaWaylandBufferRef altogether, move the use count tracking
to MetaWaylandBuffer itself. Much simpler, and doesn't run into
lifetime issues when mutter shuts down.
v4:
* Warn if use count isn't 0 in meta_wayland_buffer_finalize.
* Keep pending_buffer_resource_destroyed for attached but not yet
committed buffers. If the client attaches a buffer and then destroys
it before commit, we ignore the buffer attachement, same as before
this MR.
v5:
* Rebase on top of new commit which splits up surface->texture.
* MetaWaylandSurfaceState::buffer can only be non-NULL if
::newly_attached is TRUE, simplify accordingly.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
From xdg_surface_constructor_get_popup / xdg_popup_reposition (called
during Wayland protocol processing) to finish_popup_setup /
meta_wayland_xdg_popup_apply_state (called when the popup state is
applied).
This makes sure that the parent window frame rectangle is up to date in
meta_wayland_xdg_positioner_to_placement.
v2:
* Use meta_wayland_surface_state_new () in
meta_wayland_transaction_add_xdg_popup_reposition.
v3:
* Move xdg_popup_repositioned handling to
meta_wayland_xdg_popup_apply_state.
v4:
* Do not steal pending->xdg_positioner in
meta_wayland_xdg_popup_apply_state, fixes leaking the corresponding
memory.
* Drop MetaWaylandSurfaceState::xdg_popup_repositioned, just use
::xdg_positioner.
v5:
* Reformat meta_wayland_xdg_positioner_to_placement calls to stay within
80 columns. (Jonas Ådahl)
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
Preparation for potentially calling meta_wayland_transaction_apply some
time after surface commit, in which case doing it in the former would be
too late: The client may legally destroy the attached wl_buffer
immediately after commit, in which case meta_wayland_buffer_attach would
spuriously fail and disconnect the client (or possibly even crash mutter
due to NULL error).
Requires splitting up the surface texture between protocol and output
state, and propagating from the former to the latter via
MetaWaylandSurfaceState.
v2: (Jonas Ådahl)
* Move meta_wayland_surface_get_texture call to separate line.
* Use g_autoptr for GError.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
And keep track of the hierarchy separately for the Wayland protocol and
for output. Protocol state is updated immediately as protocol requests
are processed, output state only when the corresponding transaction is
applied (which may be deferred until the next commit of the parent
surface).
v2:
* Directly add placement ops to a transaction, instead of going via
pending_state.
* Use transaction entry for the sub-surface instead of that for its
parent surface.
v3:
* Use transaction entry for the parent surface again, to ensure proper
ordering of placement ops, and call
meta_wayland_surface_notify_subsurface_state_changed only once per
parent surface.
* Drop all use of wl_resource_add_destroy_listener, transactions are
keeping surfaces alive as long as needed.
v4:
* Rebase on https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2501
* Drop ClutterActor code from meta_wayland_surface_apply_placement_ops.
(Robert Mader)
v5:
* Rename MetaWaylandSubSurfaceState to MetaWaylandSurfaceSubState, since
the next commit adds not sub-surface specific state to it.
v6:
* Move include of meta-wayland-subsurface.h from
meta-wayland-transaction.c to .h, since the latter references
MetaWaylandSubsurfacePlacementOp.
v7:
* Drop superfluous !entry check from meta_wayland_transaction_apply.
v8:
* Rename output/protocol fields to output/protocol_state. (Jonas Ådahl)
v9:
* Use meta_wayland_surface_state_new in
meta_wayland_transaction_add_placement_op.
v10:
* Fix a few style issues per check-style.py.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
Instead of cached_state.
surface_commit for a synchronized sub-surface either commits the
transaction or merges it into the parent surface's transaction (if
the parent is a synchronized sub-surface itself).
This should fix or at least improve the behaviour of nested synchronized
sub-surfaces.
Also change wl_subsurface_set_desync:
* Commit sub-surface transactions separately. This may allow some of
them to be applied earlier in some cases.
* Commit transaction only for descendant sub-surfaces which become
newly de-synchronized themselves.
v2:
* Drop unused function prototypes
v3:
* Use g_clear_pointer for surface->sub.transaction.
v4:
* Use g_steal_pointer instead of g_clear_pointer. (Sebastian Wick, Jonas
Ådahl)
v5: (Carlos Garnacho)
* Add spaces between type casts and values.
* Use (gpointer *) instead of (void**).
v6: (Jonas Ådahl)
* Use g_clear_object in meta_wayland_transaction_entry_merge_into.
* Use meta_wayland_transaction_entry_free in
meta_wayland_transaction_merge_into.
* Fix alignment of meta_wayland_transaction_merge_pending_state
parameters.
* Remove unused meta_wayland_transaction_add_state declaration.
v7:
* Use meta_wayland_surface_state_new in
meta_wayland_transaction_merge_pending_state.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
A transaction contains the committed state for a surface, plus any
cached state for synchronized subsurfaces.
v2:
* Handle sub-surface positions separately from surface states.
v3:
* Sync child states only for surfaces with state in the transaction.
v4: (Jonas Ådahl)
* Drop unnecessary g_object_new call from wl_subsurface_set_desync. (me)
* Fix indentation & formatting in meta_wayland_surface_commit.
* Add meta_wayland_surface_state_new helper function.
* Fix alignment of meta_wayland_transaction_apply_subsurface_position
parameters.
* Add curly braces around meta_wayland_transaction_sync_child_states
call in meta_wayland_transaction_apply.
v5:
* Make meta_wayland_surface_state_new an inline function.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
If multiple transactions have entries for the same surface, they are
applied in the same order as they were committed. Otherwise, they can
be applied in any order.
This is preparation for following changes, transactions are still
applied as soon as they're committed.
v2:
* Move GQueue for transactions to MetaWaylandCompositor (Jonas Ådahl)
v3
* Say "entry for" instead of "state for", since there can be transaction
entries with no state (for surfaces which are getting destroyed).
v4:
* Use a hash table to keep track of all candidate transactions which
might be newly ready to be applied.
* Use clearer function / variable names.
v5:
* Use custom single-linked list instead of hash table for candidate
transactions, ordered by the transaction commit sequence number, so
that they're attempted to be applied in the same order as they were
committed.
* Rename transaction->queue to transaction->committed_queue, and
simplify its handling.
v6: (Carlos Garnacho)
* Add spaces between type casts and values.
* Use (gpointer *) instead of (void**).
v7: (Jonas Ådahl)
* Use G_MAXSIZE instead of ULONG_MAX.
* Fix indentation of meta_wayland_transaction_apply &
meta_wayland_transaction_maybe_apply_one parameters.
* Refactor find_next_transaction_for_surface & ensure_next_candidate
helper functions out of meta_wayland_transaction_apply.
* Refactor has_unapplied_dependencies helper function out of
meta_wayland_transaction_maybe_apply_one.
* Make while (TRUE) loop in meta_wayland_transaction_maybe_apply
consistent with general usage.
* Drop unused value local from meta_wayland_transaction_commit.
* Store pointer to compositor object in transactions, instead of
pointer to the queue of committed transactions.
* Drop tautological g_assert from meta_wayland_transaction_apply. (me)
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
v2:
* Use single hash table with struct which will contain all kinds of
state handled by a transaction.
v3:
* Add meta_wayland_transaction_destroy.
v4 (Georges Basile Stavracas Neto)
* Fix struct _MetaWaylandTransaction(Entry) formatting.
* Explicitly test against NULL.
* Use gpointer insteadof void * for
meta_wayland_transaction_entry_destroy.
v5: (Robert Mader)
* Use for loop in is_ancestor.
* Include meta-wayland-transaction.h first in
meta-wayland-transaction.c.
v6:
* Use g_autofree & g_clear_object.
v7: (Jonas Ådahl)
* Rename meta_wayland_transaction_entry_destroy to
meta_wayland_transaction_entry_free.
* Drop g_autofree use from meta_wayland_transaction_entry_free again.
* Make meta_wayland_transaction_entry_free take a
MetaWaylandTransactionEntry pointer.
* Rename meta_wayland_transaction_destroy to
meta_wayland_transaction_free.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
In fcfe90aa, multiple for loops were replaced with
META_WAYLAND_SURFACE_FOREACH_SUBSURFACE.
However, this substitution was not side-effect free, and introduced a
null-pointer dereference risk as shown in the example below:
Old:
for (n = g_node_first_child (surface->subsurface_branch_node);
n;
n = g_node_next_sibling (n))
{
if (G_NODE_IS_LEAF (n))
continue;
meta_wayland_surface_update_outputs_recursively (n->data);
}
n is checked for NULL during each loop in the condition expression.
Therefore, when `G_NODE_IS_LEAF (n)` is called, `n` is guaranteed not to
be NULL. Note also that g_node_first_child is also NULL-safe since it
performs a NULL check internally.
New:
META_WAYLAND_SURFACE_FOREACH_SUBSURFACE (surface, subsurface_surface)
meta_wayland_surface_update_outputs_recursively (subsurface_surface);
=
for (GNode *G_PASTE(__n, __LINE__) = meta_get_first_subsurface_node ((surface)); \
(subsurface = (G_PASTE (__n, __LINE__) ? G_PASTE (__n, __LINE__)->data : NULL)); \
G_PASTE (__n, __LINE__) = meta_get_next_subsurface_sibling (G_PASTE (__n, __LINE__)))
In the new logic `subsurface` is still checked for NULL in the loop
condition. However, in the new loop init:
...
meta_get_first_subsurface_node (MetaWaylandSurface *surface)
...
n = g_node_first_child (surface->subsurface_branch_node);
if (!G_NODE_IS_LEAF (n))
...
The above implementation performs a `G_NODE_IS_LEAF` call, which
performs a dereference on `n`, without first checking for NULLs.
This NULL dereference triggers the following gnome-shell crash:
Core was generated by `/usr/bin/gnome-shell'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 meta_get_first_subsurface_node (surface=0x55d589623450) at ../src/wayland/meta-wayland-surface.h:399
#1 pointer_can_grab_surface (pointer=0x7f6dc4012700, surface=0x55d589623450) at ../src/wayland/meta-wayland-pointer.c:1306
#2 0x00007f6ddb94d509 in meta_wayland_pointer_can_grab_surface (pointer=<optimized out>, surface=surface@entry=0x55d589623450, serial=serial@entry=996) at ../src/wayland/meta-wayland-pointer.c:1321
#3 0x00007f6ddb950d05 in meta_wayland_seat_get_grab_info (seat=seat@entry=0x55d586c24f20, surface=0x55d589623450, serial=996, require_pressed=require_pressed@entry=0, x=x@entry=0x0, y=y@entry=0x0)
at ../src/wayland/meta-wayland-seat.c:467
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2655>
First make sure we call 'move_resize()' in all cases where the size or
position can change, then move the updating of the buffer rect to the
same place as we update the frame rect. This means keeping track of
surface size changes, in addition to geometry changes, and calling
finish_move_resize() whenever any of those changes, in addition to
acknowledged configurations.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2338>
Add `sync_effects_completed()` and `verify_view()` in
order to allow Wayland test clients to trigger verifications
and add convenience functions to use them to client-utils.
Notes:
- `sync_effects_completed()` works in two stages in order
to ensure it doesn't race with window effects. By the time
`sync_effects_completed()` is processed, an effect could
already have ended or not yet been scheduled. Thus we
defer a check for pending effects to the next paint cycle,
assuming that by then they should have been scheduled.
- `meta_ref_test_verify_view()` internally triggers the
`paint` signal for the stage which is why it can not be run
in the after-paint signal handler.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1055>
Before scanning out the surface of a native client we have
to check the following attributes that influence the
relationship between buffer and the defined result on screen:
- buffer scale
- buffer transform
- viewport
In the future we can loose these checks again in cases where the
display hardware supports the required operations (scaling, cropping
and rotating).
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2276>
Unlike other subsurface state, placement operations need to get
applied in order. As per spec:
```
Requests are handled in order and applied immediately to a pending
state. The final pending state is copied to the active state the
next time the state of the parent surface is applied.
```
Having placement operations being part of the subsurface state
makes it difficult to support arbitrary orderings. Make them
part of the parents surface pending state instead.
Closes https://gitlab.gnome.org/GNOME/mutter/-/issues/1691
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1768>
Regarding the sequence = 0 fallback: in some cases (moving a cursor
plane on atomic amdgpu) we get sequence = 0 in the page flip callback.
This seems like an amdgpu bug, so work around it by assuming a sequence
delta of 1 (it is equal to 1 because of the sequence != 0 check above).
Sequence can also legitimately be 0 if we're lucky during the 32-bit
overflow, in which case assuming a delta of 1 will give more or less
reasonable values on this and next presentation, after which it'll be
back to normal.
Sequence is also 0 on mode set fallback and when running nested, in
which case assuming a delta of 1 every frame is the best we can do.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1484>
The presentation-time protocol allows surfaces to get accurate
timestamps of when their contents were shown on screen.
This commit implements a stub version of the protocol which correctly
discards all presentation feedback objects (as if the surface contents
are never shown on screen). Subsequent commits will implement sending
the presented events to surfaces shown on screen.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1484>
There's no need to update the outputs recursively in case the actor gets
mapped or unmapped. That's because mapping happens recursively itself,
so if a window with multiple subsurfaces is shown, all subsurfaces will
receive a "notify::mapped" signal.
Since this was the only remaining user of
meta_wayland_surface_update_outputs_recursively(), we can now remove
that function.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1358
Since we're now connecting to one more signal of MetaWaylandOutput, keep
signal connections in one place and move connecting the
"output-destroyed" signal to surface_entered_output() and disconnecting
it to surface_left_output().
This also allows us to use the "outputs_to_destroy_notify_id" as a
simple set and rename it to "outputs".
While at it, also use g_hash_table_destroy() instead of
g_hash_table_unref() since destroy is more clear than unref and does the
same thing in this case.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1230
This will check whether the current backing buffer is compatible with
the primary plane of the passed CoglOnscreen. Since this will extend the
time before a buffer is released, the MetaWaylandBufferRef is swapped
and orphaned if a new buffer is committed before the previous one was
released. It'll eventually be released, usually by the next page flip
callback.
Currently implemented for EGLImage and DMA-BUF buffer types.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/798
Currently a buffer use count always reaches zero before it is replaced.
This is due to the fact that at the point a new buffer is attached, the
last potential user releases it (the stage) since the currently
displayed frame has a composited copy of the buffer.
This may however change, if a buffer is scanned out directly, meaning it
should not be released until the page flip callback is invoked.
Prepare for this by making the buffer reference a heap allocated struct,
enabling us to keep a pointer to it longer than the buffer is attached.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/798
There are two surface roles owning a MetaWindow: MetaWaylandShellSurface
(basis of MetaWaylandXdgToplevel, MetaWaylandXdgPopup,
MetaWaylandWlShellSurface, etc), and MetaXwaylandSurface.
With these two role types, the MetaWindow has two different types of
life times. With MetaWaylandShellSurface, the window is owned and
managed by the role itself, while with MetaXwaylandSurface, the
MetaWindow is tied to the X11 window, while the Wayland surface and its
role plays more the role of the backing rendering surface.
Before, for historical reasons, MetaWindow was part of
MetaWaylandSurface, even though just some roles used it, and before
'wayland: Untie MetaWindowXwayland lifetime from the wl_surface' had
equivalent life times as well. But since that commit, the management
changed. To not have the same fied in MetaWaylandSurface being managed
in such drastically different ways, rearrange it so that the roles that
has a MetaWindow themself manages it in the way it is meant to; meaning
MetaWaylandShellSurface practically owns it, while with Xwayland, the
existance of a MetaWindow is tracked via X11.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/835
The role determines how a relative coordinate is calculated. More
specifically, using clutters API to transform coordinates is only
accurate right after a clutter layout pass but this function is used
e.g. to deliver pointer motion events which can happen at any time. This
isn't a problem for Wayland clients since they don't control their
position, but X clients do and we'd be sending outdated coordinates if a
client is moving a window in response to motion events.
This was already done already, but now move the Xwayland specific logic
to the Xwayland surface role, keeping the generic transformation logic
in the generic actor surface role.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/835
The shell surface role is the one where subsurfaces may exist, and it
has direct relation to the MetaWindowActorWayland which currently has
the subsurface stacking logic.
Instead of directly finding the window actor when dealing with
subsurfaces, notify the parent surface that the subsurface state
changed, so that it can outsource the application of this information to
the role. For subsurface roles, this simply means forward upward to the
parent; for shell surface roles, this means regenerate the surface actor
layering.
This allows us to move away from accessing the window directly from the
surface, which in turn allows us to change the ownership structure of
windows.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/835
Similar to wl_list_foreach(), add
META_WAYLAND_SURFACE_FOREACH_SUBSURFACE() that iterates over all the
subsurfaces of a surface, without the caller needing to care about
implementation details, such as leaf nodes vs non-leaf nodes.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/961
The vfunc is not called when a surface commits its state, but when the
state is applied. Make this clearer by changing the name to
"apply_state" (and "pre_apply_state").
https://gitlab.gnome.org/GNOME/mutter/merge_requests/907
This changes how asynchronous window configuration works. Prior to this
commit, it worked by MetaWindowWayland remembering the last
configuration it sent, then when the Wayland client got back to it, it
tried to figure out whether it was a acknowledgment of the configuration
or not, and finish the move. This failed if the client had acknowledged
a configuration older than the last one sent, and it had hacks to
somewhat deal with wl_shell's lack of configuration serial numbers.
This commits scraps that and makes the MetaWindowWayland take ownership
of sent configurations, including generating serial numbers. The
wl_shell implementation is changed to emulate serial numbers (assuming
each commit acknowledges the last sent configure event). Each
configuration sent to the client is kept around until the client one. At
this point, the position used for that particular configuration is used
when applying the acknowledged state, meaning cases where we have
already sent a new configuration when the client acknowledges a previous
one, we'll still use the correct position for the window.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/907
This moves the cached subsurface surface state into the generic
MetaWaylandSurface namespace. Eventually it'll be used by other surface
roles which as well aim to implement synhcronization.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/907
The name didn't communicate it was about surface state, and it somewhat
confusingly had the name "pending" in it, which could be confused with
the fact that while it's used to collect pending state, it's also used
to cache previously committed pending state.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/907
With the eventual aim of exposing the internals of MetaWaylandSurface
outside of meta-wayland-surface.c, make users of the pending state use a
helper to fetch it. While at it, rename the struct field to something
more descriptive.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/907
For the most part, a MetaWindow is expected to live roughly as long as
the associated wl_surface, give or take asynchronous API discrepancies.
The exception to this rule is handling of reparenting when decorating or
undecorating a window, when a MetaWindow on X11 is made to survive the
unmap/map cycle. The fact that this didn't hold on Wayland caused
various issues, such as a feedback loop where the X11 window kept being
remapped. By making the MetaWindow lifetime for Xwayland windows being
the same as they are on plain X11, we remove the different semantics
here, which seem to lower the risk of hitting the race condition causing
the feedback loop mentioned above.
What this commit do is separate MetaWindow lifetime handling between
native Wayland windows and Xwayland windows. Wayland windows are handled
just as they were, i.e. unmanaged together as part of the wl_surface
destruction; while during the Xwayland wl_surface destruction, the
MetaWindow <-> MetaWaylandSurface association is simply broken.
Related: https://gitlab.freedesktop.org/xorg/xserver/issues/740
Fixes: https://gitlab.gnome.org/GNOME/mutter/issues/762https://gitlab.gnome.org/GNOME/mutter/merge_requests/774
Flatten the subsurface actor tree, making all surface actors children
of the window actor.
Save the subsurface state in a GNode tree in MetaWaylandSurface, where
each surface holds two nodes, one branch, which can be the tree root
or be attached to a parent surfaces branch, and a leaf, which is
used to save the position relative to child branch nodes.
Each time a surface is added or reordered in the tree, unparent all
surface actors from the window actor, traverse all leaves of the
tree and readd the corresponding surface actors back to the window
actor.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/664
Prior to this commit, MetaWaylandSurface held a reference to
MetaWaylandBuffer, who owned the texture drawn by the surface. When
switching buffer, the texture change with it.
This is problematic when dealing with SHM buffer damage management, as
when having one texture per buffer, damaged regions uploaded to one,
will not follow along to the next one attached. It also wasted GPU
memory as there would be one texture per buffer, instead of one one
texture per surface.
Instead, move the texture ownership to MetaWaylandSurface, and have the
SHM buffer damage management update the surface texture. This ensures
damage is processed properly, and that we won't end up with stale
texture content when doing partial texture uploads. If the same SHM
buffer is attached to multiple surfaces, each surface will get their own
copy, and damage is tracked and uploaded separately.
Non-SHM types of buffers still has their own texture reference, as the
texture is just a representation of the GPU memory associated with the
buffer. When such a buffer is attached to a surface, instead the surface
just gets a reference to that texture, instead of a separately allocated
one.
Fixes: https://gitlab.gnome.org/GNOME/mutter/issues/199
This adds the required bits to wayland surfaces and ties them up
to the compositor parts.
It is based on and very similar in nature to buffer transforms.
From the specification:
> The global interface exposing surface cropping and scaling
> capabilities is used to instantiate an interface extension for a
> wl_surface object. This extended interface will then allow cropping
> and scaling the surface contents, effectively disconnecting the
> direct relationship between the buffer and the surface size.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/323
This adds the required bits to wayland surfaces and ties them up
to the compositor parts.
The central part here is to recalculate the surface size accordingly
and to translate surface damage into buffer damage.
The choosen approach additionally lays groundwork for wp_viewporter
support, which is closely related in its nature.
A further explanation of buffer transforms from the specification:
> The purpose of this request is to allow clients to render content
> according to the output transform, thus permitting the compositor
> to use certain optimizations even if the display is rotated.
> Using hardware overlays and scanning out a client buffer for
> fullscreen surfaces are examples of such optimizations.
It is meant to hold surfaces that require a ClutterActor, just like wl/xdg
shell surfaces and subsurfaces. Make it inherit from MetaWaylandActorSurface
so it gets that for free.
The type declaration is also made completely private, in order to avoid
cyclic dependency between meta-wayland-surface.h and
meta-wayland-actor-surface.h. We just require the GType fro assign_role()
anyway.
