Most of the pending output state is not forwarded to the backend prior
to an output commit. For instance, wlr_output_set_mode just stashes the
mode without calling any wlr_output_impl function.
wlr_output_impl.commit is responsible for applying the pending mode.
However, there are exceptions to this rule. The first one is
wlr_output_attach_render. It won't go away before renderer v6 is
complete, because it needs to set the current EGL surface.
The second one is wlr_output_attach_buffer.
wlr_output_impl.attach_buffer is removed in [1].
When wlr_output_rollback is called, all pending state is supposed to be
cleared. This works for all the state except the two exceptions
mentionned above. To fix this, introduce wlr_output_impl.rollback.
Right now, the backend resets the current EGL surface. This prevents GL
commands from affecting the output after wlr_output_rollback.
This patch is required for FBO-based outputs to work properly. The
compositor might be using FBOs for its own purposes [2], having leftover
FBO state can have bad consequences.
[1]: https://github.com/swaywm/wlroots/pull/2097
[2]: https://github.com/swaywm/wlroots/pull/2063#issuecomment-597614312
Check that buffer can be scanned out in wlr_output_test instead of
wlr_output_attach_buffer. This allows the backend to have access to the
whole pending state when performing the check.
This brings the wlr_output API more in line with the KMS API.
This removes the need for wlr_output_attach_buffer to return a value,
and for wlr_output_impl.attach_buffer.
Consumers call wlr_buffer_lock. Once all consumers are done with the
buffer, only the producer should have a reference to the buffer. In this
case, we can release the buffer (and let the producer re-use it).
The logind provider defaulted to systemd and in order to use elogind,
-Dlogin-provider=elogind was required. This adds 'auto' as a choice
for the login-provider option and sets it as default. Using 'auto',
the build will check for systemd first and if it's not found, try
to find and use elogind automatically.
Previously, each time a wl_seat.capabilities event was received the
Wayland backend created new input devices. It now only does so the first
time.
Input devices are now destroyed when the cap is removed.
Closes: https://github.com/swaywm/sway/issues/5055
This function allowed backends to provide a custom function for frame
scheduling. Before resuming the rendering loop, the DRM and Wayland
backends would wait for vsync.
There isn't a clear benefit of doing this. The only upside is that we
get more stable timings: the delay between two repaints doesn't change too
much and is close to a mutliple of the refresh rate.
However this introduces latency, especially when a client misses a
frame. For instance a fullscreen game missing vblank will need to wait
more than a whole frame before being able to display new content. This
worst case scenario happens as follows:
- Client is still rendering its frame and cannot submit it in time
- Deadline is reached
- Compositor decides to stop the rendering loop since nothing changed on
screen
- Client finally manages to render its frame, submits it
- Compositor calls wlr_output_schedule_frame
- DRM backend waits for next vblank
- The wlr_output frame event is fired, compositor draws new content on screen
- On the second next vblank, the new content reaches the screen
With this patch, the wlr_output frame event is fired immediately when
the client submits its late frame.
This change also makes it easier to support variable refresh rate, since
VRR is all about being able to present too-late frames earlier.
References: https://github.com/swaywm/wlroots/issues/1925
The previous PR was overzealous in adding a finish_drm_surface call
which was also done by the caller. Remove the call and also move the
comment to the correct code location.
In some cases modesets fail if the planes are initialized with
modifiers. Since in this case possibly all planes need to reinitialized,
which is not possible in the current wlroots design, add an environment
variable for affected users.
Previously, an error on the remote Wayland display would result in an
infinite loop priting:
2020-01-09 13:39:03 - [wayland] Source dispatch function returned negative value!
2020-01-09 13:39:03 - [wayland] This would previously accidentally suppress a follow-up dispatch
This happens when the remote compositor disconnects the client because
of a protocol error, for instance.
Handle wl_display_dispatch and wl_display_dispatch_pending returning -1
by terminating the local display and printing an error.
Previously, we just assumed submitting a new frame would make the
compositor release the current one. This isn't always the case, for
instance Sway retains old buffers when a transaction is pending. This
resulted in synchronization issues with clients writing in
front-buffers.
Fix this by un-referencing a wlr_buffer when the parent compositor sends
wl_buffer.release.
Tested by running a fullscreen mpv instance in Sway with the Wayland
backend.
This fixes a segfault in drm_connector_set_mode (mode = NULL).
This happens because we set wlr_output.enabled to true if the connector
is attached to the CRTC. When the user disables an output in the
wlroots-based compositor, switches to another VT (enabling the output),
then switches back, wlroots sets wlr_output.enabled to true but
wlr_output.current_mode is NULL.
We should consider not reading properties from KMS after a TTY switch,
disabling all connectors. However this may result in flickering (outputs
being disabled then re-enabled).
Closes: https://github.com/swaywm/wlroots/issues/1874
wlr_output.description is a string containing a human-readable string
identifying the output. Compositors can customise it via
wlr_output_set_description, for instance to make the name more
user-friendly.
References: https://github.com/swaywm/wlroots/issues/1623
Bumps minimum version to 0.51.0
- Remove all intermediate static libraries.
They serve no purpose and are just add a bunch of boilerplate for
managing dependencies and options. It's now managed as a list of
files which are compiled into libwlroots directly.
- Use install_subdir instead of installing headers individually.
I've changed my mind since I did that. Listing them out is annoying as
hell, and it's easy to forget to do it.
- Add not_found_message for all of our optional dependencies that have a
meson option. It gives some hints about what option to pass and what
the optional dependency is for.
- Move all backend subdirectories into their own meson.build. This
keeps some of the backend-specific build logic (especially rdp and
session) more neatly separated off.
- Don't overlink example clients with code they're not using.
This was done by merging the protocol dictionaries and setting some
variables containing the code and client header file.
Example clients now explicitly mention what extension protocols they
want to link to.
- Split compositor example logic from client example logic.
- Minor formatting changes
Previously, the path of TTY is generated using snprintf with %d format.
It works with TTY 1 to 10, but fails with TTY with greater number
because the number used in the name is in base 32 instead of base 10.
Since there is no standard function to convert a number to a string with
a custom base, this commit adds a function to do it.
Fixes: https://github.com/swaywm/wlroots/issues/1854
Remove glapi.sh code generation, replace it with hand-written loading
code that checks extension strings before calling eglGetProcAddress.
The GLES2 renderer still uses global state because of:
- {PUSH,POP}_GLES2_DEBUG macros
- wlr_gles2_texture_from_* taking a wlr_egl instead of the renderer
This fixes a heap-use-after-free when the session is destroyed before
the backend during wl_display_destroy:
==1085==ERROR: AddressSanitizer: heap-use-after-free on address 0x614000000180 at pc 0x7f88e3590c2d bp 0x7ffdc4e33f90 sp 0x7ffdc4e33f80
READ of size 8 at 0x614000000180 thread T0
#0 0x7f88e3590c2c in find_device ../subprojects/wlroots/backend/session/session.c:192
#1 0x7f88e3590e85 in wlr_session_close_file ../subprojects/wlroots/backend/session/session.c:204
#2 0x7f88e357b80c in libinput_close_restricted ../subprojects/wlroots/backend/libinput/backend.c:24
#3 0x7f88e21af274 (/lib64/libinput.so.10+0x28274)
#4 0x7f88e21aff1d (/lib64/libinput.so.10+0x28f1d)
#5 0x7f88e219ddac (/lib64/libinput.so.10+0x16dac)
#6 0x7f88e21b415d in libinput_unref (/lib64/libinput.so.10+0x2d15d)
#7 0x7f88e357c9d6 in backend_destroy ../subprojects/wlroots/backend/libinput/backend.c:130
#8 0x7f88e3545a09 in wlr_backend_destroy ../subprojects/wlroots/backend/backend.c:50
#9 0x7f88e358981a in multi_backend_destroy ../subprojects/wlroots/backend/multi/backend.c:54
#10 0x7f88e358a059 in handle_display_destroy ../subprojects/wlroots/backend/multi/backend.c:107
#11 0x7f88e314acde (/lib64/libwayland-server.so.0+0x8cde)
#12 0x7f88e314b466 in wl_display_destroy (/lib64/libwayland-server.so.0+0x9466)
#13 0x559fefb52385 in main ../main.c:67
#14 0x7f88e2639152 in __libc_start_main (/lib64/libc.so.6+0x27152)
#15 0x559fefb4297d in _start (/home/simon/src/glider/build/glider+0x2297d)
0x614000000180 is located 320 bytes inside of 416-byte region [0x614000000040,0x6140000001e0)
freed by thread T0 here:
#0 0x7f88e3d0a6b0 in __interceptor_free /build/gcc/src/gcc/libsanitizer/asan/asan_malloc_linux.cc:122
#1 0x7f88e35b51fb in logind_session_destroy ../subprojects/wlroots/backend/session/logind.c:270
#2 0x7f88e35905a4 in wlr_session_destroy ../subprojects/wlroots/backend/session/session.c:156
#3 0x7f88e358f440 in handle_display_destroy ../subprojects/wlroots/backend/session/session.c:65
#4 0x7f88e314acde (/lib64/libwayland-server.so.0+0x8cde)
previously allocated by thread T0 here:
#0 0x7f88e3d0acd8 in __interceptor_calloc /build/gcc/src/gcc/libsanitizer/asan/asan_malloc_linux.cc:153
#1 0x7f88e35b911c in logind_session_create ../subprojects/wlroots/backend/session/logind.c:746
#2 0x7f88e358f6b4 in wlr_session_create ../subprojects/wlroots/backend/session/session.c:91
#3 0x559fefb51ea6 in main ../main.c:20
#4 0x7f88e2639152 in __libc_start_main (/lib64/libc.so.6+0x27152)
This requires functions without a prototype definition to be static.
This allows to detect dead code, export less symbols and put shared
functions in headers.
This reverts commit 3317134adf.
This reverts commit a3c3b928a3.
There are some serious issues when running this on a real X server, as
opposed to running this on Xwayland, where this was tested.
More investigation needs to be done into why these issues happen and if
our usage of the present extension is correct.
This is set to the value of wlr_output.commit_seq when the frame has
been submitted. This allows tracking presentation with more then 1 full
frame of latency.
References: https://github.com/swaywm/wlroots/issues/1917
Expose the remote wl_display, wl_surface and wl_seat used by the Wayland
backend.
This allows compositors to customize the Wayland backend and to have
more freedom. For instance a compositor might want to handle clipboard
and drag-and-drop from the remote Wayland compositor. Another compositor
might want to setup pointer constraints.
We just send relative motion events alongside absolute motion events.
Compositors can figure out how absolute and relative events are related
(e.g. whether they have been triggered by the same logical event) with
the frame event.
Makes use of the present extension to get notified of vsync, and not
require any stupid timer hacks. Also make use of the present version of
ConfigureNotify, because why not?
This allows wlroots based compositors to properly use graphic tablets
with the wayland backend.
This should be a decent quality of life improvement when working on
tablet related features.
Instead of checking that the path property is not 0 to determine if the
connector is an MST connector, check if the path contains the mst:
string.
Fixes#1813
libinput_event_touch_get_slot always returns -1 for single touch devices. Using
libinput_event_touch_get_seat_slot instead ensures that they are assigned actual
slot ids.
Also, this is what Weston does, so this change yields a more consistent
behaviour between different compositors.
Instead of waiting for the next pageflip, destroy the output immediately
since we can now handle flips for outputs which no longer exist.
Also demote the missing crtc on flip to debug.
Fixes#1739
This commit makes more output properties (mode, enabled, scale and transform)
atomic. This means that they are double-buffered and only applied on commit.
Compositors now need to call wlr_output_commit after setting any of those
properties.
Internally, backends still apply properties sequentially. The behaviour should
be exactly the same as before. Future commits will update some backends to take
advantage of the atomic interface. Some backends are non-atomic by design, e.g.
the X11 backend or the legacy DRM backend.
Updates: https://github.com/swaywm/wlroots/issues/1640
The documentation for wayland-server.h says:
> Use of this header file is discouraged. Prefer including
> wayland-server-core.h instead, which does not include the server protocol
> header and as such only defines the library PI, excluding the deprecated API
> below.
Replacing wayland-server.h with wayland-server-core.h allows us to drop the
WL_HIDE_DEPRECATED declaration.
atomic and legacy now both pass the backend as the user data for the
pageflip event. We than retrieve the correct connector by matching on
the crtc_id passed to the page_flip_handler2.
Wlroots also requires the DRM_CRTC_IN_VBLANK_EVENT capability now.
Fixes#1297
The backend doesn't need to handle transform changes, since everything is done
in software. In fact, all of the implementations were all identical and just
set the transform.
We could add support for hardware transforms, but:
- This would require a different field (something like hardware_transform)
- Not all combinations are possible because there often are hardware
limitations
- The Wayland protocol isn't ready for this (in particular xdg-output, see [1])
This belongs to a different patch series anyway.
[1]: https://patchwork.freedesktop.org/series/52324/
The DRM subsystem needs a NULL modeset for connectors which disappear
from the system to disable the hardware pipes, otherwise the pixels get
rendered but are sent nowhere.
The atomic backend does the equivalent by removing the properties and
issuing a commit.
Fixes#1706
In order to support compositors running as systemd user units without display manager,
a mechanism for specifying session ID exactly must exist.
Checking for `XDG_SESSION_ID` mimics loginctl behaviour e95be7def2/src/login/loginctl.c (L856).
"/org/freedesktop/login1/seat/self" path triggers seat-finding code path in logind,
which currently relies on getting the session based on caller's PID.
This behaviour is deprecated in logind as it doesn't work eg. with systemd user units,
which run outside of user session.
We check for "seat0" in logind_change_vt() already as introduced in 47985d2dc5,
so hard-coding it here is not a problem, otherwise sd_session_get_seat() could be used.
When using the rdp backend and connecting with xfreerdp ... --rfx, wlroots
crashes in backend/rdp/output.c while attempting to realloc(..., 0).
This commit guards against that and instead returns true, resulting in
no rfx message being sent. This prevents the crash and appears to work, but
it's not obvious if this is correct from a specification perspective.
This appears to be a quick fix for compositors freezing when a dock is
disconnected. Disconnection of the dock is causing `pause_device` for
the DRM devices associated with the dock. Since these devices major
number is `DRM_MAJOR`, the session was being set to inactive. This just
makes it so the session is not set to inactive when the device's state
is `gone`.
This updates the backend part of the output API. This is mostly renaming:
make_current becomes attach_render and swap_buffers becomes commit.
This also fixes the RDP backend to support NULL damage.
The deleted includes are redundant, because other headers will include
the necessary files. Additionally, they cause build failures, because
including EGL/egl.h or EGL/eglext.h directly, instead of through
wlr/render/egl.h or wlr/render/interface.h, will mean that
MESA_EGL_NO_X11_HEADERS will not have been defined, and so the EGL
headers will attempt to pull in unnecessary X11 headers that may not
exist on the system.
For the headers produced by glgen.sh, the includes couldn't simply be
deleted, because no other header would include the EGL headers. Neither
wlr/render/egl.h or wlr/render/interface.h felt appropriate to include,
so I opted instead to copy the MESA_EGL_NO_X11_HEADERS definition before
the EGL includes.
backend/headless/output.c:132:3: error: format specifies type 'long' but the argument has type 'size_t' (aka 'unsigned int') [-Werror,-Wformat]
++backend->last_output_num);
^~~~~~~~~~~~~~~~~~~~~~~~~~
backend/noop/output.c:72:3: error: format specifies type 'long' but the argument has type 'size_t' (aka 'unsigned int') [-Werror,-Wformat]
++backend->last_output_num);
^~~~~~~~~~~~~~~~~~~~~~~~~~
backend/wayland/output.c:294:3: error: format specifies type 'unsigned long' but the argument has type 'size_t' (aka 'unsigned int') [-Werror,-Wformat]
++backend->last_output_num);
^~~~~~~~~~~~~~~~~~~~~~~~~~
backend/x11/output.c:150:3: error: format specifies type 'long' but the argument has type 'size_t' (aka 'unsigned int') [-Werror,-Wformat]
++x11->last_output_num);
^~~~~~~~~~~~~~~~~~~~~~
* wlr_output: Indicate modes link
* wlr_output: Introduce preferred flag
This indicates an outputs preferred mode.
* drm: Set preferred flag for an outputs preferred mode
This improves the way the output numbers are handled for the noop
backend. Instead of using the number of active outputs plus one, the
last used number is stored and new outputs will increment it. This
fixes the situation where you start with one output, create a second,
close the first, and create a third. Without this, both outputs will be
NOOP-2, which causes an issue since the identifier will also be
identical. With this, the last output is NOOP-3 and the outputs can be
distinguished.
This improves the way the output numbers are handled for the headless
backend. Instead of using the number of active outputs plus one, the
last used number is stored and new outputs will increment it. This
fixes the situation where you start with one output, create a second,
close the first, and create a third. Without this, both outputs will be
HEADLESS-2, which causes an issue since the identifier will also be
identical. With this, the last output is HEADLESS-3 and the outputs can
be distinguished.
This improves the way the output numbers are handled for the x11
backend. Instead of using the number of active outputs plus one, the
last used number is stored and new outputs will increment it. This
fixes the situation where you start with one output, create a second,
close the first, and create a third. Without this, both outputs will be
X11-2, which causes an issue since the identifier will also be
identical. With this, the last output is X11-3 and the outputs can be
distinguished.
This improves the way the output numbers are handled for the wayland
backend. Instead of using the number of active outputs plus one, the
last used number is stored and new outputs will increment it. This
fixes the situation where you start with one output, create a second,
close the first, and create a third. Without this, both outputs will be
`WL-2`, which causes an issue since the identifier will also be
identical. With this, the last output is `WL-3` and the outputs can be
distinguished.
This is the first step towards being able to run via DRM leasing and on render
nodes.
Test with:
export WLR_BACKENDS=drm
export WLR_SESSION=noop
export WLR_DRM_DEVICES=/dev/dri/renderD128
If *changed_outputs is not supplied by the calling function, track the local
allocation with a bool variable and free the allocation at the end of the
function.
On DRM resume, such as switching back to a TTY, the output needs to be
modeset to the current mode. However, wlr_output_set_mode will return
early when attempting to set the mode to the current mode. This just
steps around wlr_output_set_mode and calls drm_connector_set_mode
directly.
There is no point in modesetting an output to a mode that it is already
set to. Modesetting will cause the output to briefly flicker which is
undesirable for a noop. This returns early in `drm_connector_set_mode`
when attempting to modeset to the current mode.
In order for a surface to be used as a cursor plane framebuffer, it
appears that requiring the buffer to be linear is sufficient.
GBM_BO_USE_SCANOUT is added in case GBM_BO_USE_LINEAR isn't sufficient
on untested hardware.
Fixes#1323
Removed wlr_drm_plane.cursor_bo as it does not serve any purpose
anymore.
Relevant analysis (taken from the PR description):
While trying to implement a fix for #1323, I found that when exporting
the rendered surface into a DMA-BUF and reimporting it with
`GBM_BO_USE_CURSOR`, the resulting object does not appear to be valid.
After some digging (turning on drm-kms debugging and switching to legacy
mode), I managed to extract the following error: ```
[drm:__setplane_check.isra.1 [drm]] Invalid pixel format AR24
little-endian (0x34325241), modifier 0x100000000000001 ``` The format
itself refers to ARGB8888 which is the same format as
`renderer->gbm_format` used in master to create the cursor bo. However,
using `gbm_bo_create` with `GBM_BO_USE_CURSOR` results in a modifier of
0. A modifier of zero represents a linear buffer while the modifier of
the surface that is rendered to is `I915_FORMAT_MOD_X_TILED` (see
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/include/uapi/drm/drm_fourcc.h?h=v4.20.6#n263).
In order to fix this mismatch in modifier, I added the
`GBM_BO_USE_LINEAR` to the render surface and everything started to work
just fine. I wondered however, whether the export and import is really
necessary. I then decided to test if the back buffer of the render
surface works as well, and at least on my hardware (Intel HD 530 and
Intel UHD 620) it does. This is the patch in this PR and this requires
no exporting and importing.
I have to note that I cheated in order to import DMA_BUFs into a cursor
bo when doing the first tests, since on import the Intel drivers check
that the cursor is 64x64. This is strange since cursor sizes other than
64x64 have been around for quite some time now
(https://lists.freedesktop.org/archives/mesa-commit/2014-June/050268.html).
Removing this check made everything work fine. I later (while writing
this PR) found out that `__DRI_IMAGE_USE_CURSOR` (to which
`GBM_BO_USE_CURSOR` translates) has been deprecated in mesa
(https://gitlab.freedesktop.org/mesa/mesa/blob/master/include/GL/internal/dri_interface.h#L1296),
which makes me wonder what the usecase of `GBM_BO_USE_CURSOR` is. The
reason we never encountered this is that when specifying
`GBM_BO_USE_WRITE`, a dumb buffer is created trough DRM and the usage
flag never reaches the Intel driver directly. The relevant code is in
https://gitlab.freedesktop.org/mesa/mesa/blob/master/src/gbm/backends/dri/gbm_dri.c#L1011-1089
. From this it seems that as long as the size, format and modifiers are
right, any surface can be used as a cursor.
When a wlroots compositor runs as a systemd user unit there is no
session associated with the compositor process. Instead we need to
attach to an active and graphical user session.
This change first looks for an available session for the process, and if
there isn't one falls back to display in the oldest available graphical
session.
This work was modeled after a similar change to mutter -
https://gitlab.gnome.org/GNOME/mutter/merge_requests/150.
We create the EGL config with GBM_FORMAT_ARGB8888, but then initialize GBM BOs
with GBM_FORMAT_XRGB8888. This mismatch confuses Mesa.
Instead, we can always use GBM_FORMAT_ARGB8888, and use DRM_FORMAT_XRGB8888
when calling drmModeAddFB2.
Fixes https://github.com/swaywm/wlroots/issues/1438
Frame events group logically connected pointer events. It makes sense to make
the backend responsible for sending frame events, since once the events are
split (ie. once the frame events are stripped) it's not easy to figure out
which events belongs to which frame again.
This is also how Weston handles frame events.
Fixes https://github.com/swaywm/wlroots/issues/1468
Set the default "wlroots - " title when the title argument to the
set_title functions is NULL. Otherwise, for at least the Wayland
backend, we'd crash because xdg_toplevel_set_title doesn't handle a NULL
pointer.
When there aren't enough CRTCs for all outputs, we try to move a CRTC from a
disabled output to an enabled one. When this happens, the old output's state
wasn't changed, so the compositor thought it was still enabled and rendering.
This commit marks the old output as WLR_DRM_CONN_NEEDS_MODESET and sets its
current mode to NULL.
The noop backend is similar to headless, but it doesn't contain a
renderer. It can be used as a place to stash views for when there's no
physical outputs connected.
As evdev-proto is installed by CI some files have been missed:
../examples/pointer-constraints.c:2:10: fatal error: 'linux/input-event-codes.h' file not found
#include <linux/input-event-codes.h>
^~~~~~~~~~~~~~~~~~~~~~~~~~~
../examples/relative-pointer-unstable-v1.c:5:10: fatal error: 'linux/input-event-codes.h' file not found
#include <linux/input-event-codes.h>
^~~~~~~~~~~~~~~~~~~~~~~~~~~
Values from libdrm are likely more reliable than raw values from the EDID. We
were already using values from libdrm, but they were overwritten by parse_edid.
See drm.c:
wlr_conn->output.phys_width = drm_conn->mmWidth;
wlr_conn->output.phys_height = drm_conn->mmHeight;
This commit changes `scan_drm_connectors` to add new outputs to the end of the
list. That way, it's easier to understand what's going on with indices.
When we need to destroy outputs, we now walk the list in reverse order. This
ensures indices remain correct while iterating and removing items from the
list.
We now also make outputs without a CRTC disappear (those are in
WLR_DRM_CONN_NEEDS_MODESET state).
The renderer redesign is going to need the render fd before the backend
is fully started, so we have to move the wl registry code to when the
backend is created instead of when it is started.
We also need to stash the wl_keyboard and emit it to library users
later, once they've added their listeners and started the backend.
There was a missing copy_drm_surface_mgpu call in drm_connector_schedule_frame
so we asked for a pageflip with an unknown BO, resulting in ENOENT.
Additionally, this commit makes schedule_frame return a bool indicating
failures. This allows schedule_frame_handle_idle_timer to only set
frame_pending to true if a frame has been successfully scheduled. Thus, if a
pageflip fails, rendering won't be blocked forever anymore.
In case a pageflip is already pending, true is returned because a frame has
already been scheduled and will be sent sometime soon.
This allows the legacy interface to be used instead of atomic if needed. This
is a workaround to make some Intel GPUs work (if this variable is unset) as
well as to make some AMD GPUs work (if this variable is set).
If a pageflip is pending before cleanup, it's still pending after. This
is used line 1177: drm_connector_cleanup is called and
conn->pageflip_pending is checked afterwards.
Fixes#1297
This prevents the idle event to be activated on a destroyed
output.
This also makes the backend responsible for free-ing modes, as it
is the one allocating them and adding them to the list. Note that
the DRM backend (the only one using modes) already frees them.
This desynchronizes our rendering loop with the vblank cycle.
In case a compositor doesn't swap buffers but schedules a frame,
emitting a frame event immediately enters a busy-loop.
Instead, ask the backend to send a frame when appropriate. On
Wayland we can just register a frame callback on our surface. On
DRM we can do a no-op pageflip.
Fixes#617Fixesswaywm/sway#2748
