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compositor: Handle fences in the frontend X connection

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Since mutter has two X connections and does damage handling on the
frontend while fence triggering is done on the backend, we have a race
between XDamageSubtract() and XSyncFenceTrigger() causing missed
redraws in the GL_EXT_X11_sync_object path.

If the fence trigger gets processed first by the server, any client
drawing that happens between that and the damage subtract being
processed and is completely contained in the last damage event box
that mutter got, won't be included in the current frame nor will it
cause a new damage event.

A simple fix for this would be XSync()ing on the frontend connection
after doing all the damage subtracts but that would add a round trip
on every frame again which defeats the asynchronous design of X
fences.

Instead, if we move fence handling to the frontend we automatically
get the right ordering between damage subtracts and fence triggers.

https://bugzilla.gnome.org/show_bug.cgi?id=728464
This commit is contained in:
Rui Matos 2015-08-12 15:26:34 +02:00
parent 55692b4019
commit 299ed424d3
3 changed files with 18 additions and 6 deletions
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3
src/backends/x11/meta-backend-x11.c
View File

@ -45,7 +45,6 @@
#include <meta/util.h>
#include "display-private.h"
#include "compositor/compositor-private.h"
#include "compositor/meta-sync-ring.h"
typedef enum {
/* We're a traditional CM running under the host. */
@ -267,8 +266,6 @@ handle_host_xevent (MetaBackend *backend,
MetaCompositor *compositor = display->compositor;
if (meta_plugin_manager_xevent_filter (compositor->plugin_mgr, event))
bypass_clutter = TRUE;
if (compositor->have_x11_sync_object)
meta_sync_ring_handle_event (event);
}
}

6
src/compositor/compositor.c
View File

@ -529,8 +529,7 @@ meta_compositor_manage (MetaCompositor *compositor)
*/
XMapWindow (xdisplay, compositor->output);
compositor->have_x11_sync_object =
meta_sync_ring_init (meta_backend_x11_get_xdisplay (META_BACKEND_X11 (backend)));
compositor->have_x11_sync_object = meta_sync_ring_init (xdisplay);
}
redirect_windows (display->screen);
@ -732,6 +731,9 @@ meta_compositor_process_event (MetaCompositor *compositor,
process_damage (compositor, (XDamageNotifyEvent *) event, window);
}
if (compositor->have_x11_sync_object)
meta_sync_ring_handle_event (event);
/* Clutter needs to know about MapNotify events otherwise it will
think the stage is invisible */
if (!meta_is_wayland_compositor () && event->type == MapNotify)

15
src/compositor/meta-sync-ring.c
View File

@ -322,7 +322,7 @@ meta_sync_new (Display *xdisplay)
self->xdisplay = xdisplay;
self->xfence = XSyncCreateFence (xdisplay, DefaultRootWindow (xdisplay), FALSE);
self->gl_x11_sync = meta_gl_import_sync (GL_SYNC_X11_FENCE_EXT, self->xfence, 0);
self->gl_x11_sync = 0;
self->gpu_fence = 0;
self->xcounter = XSyncCreateCounter (xdisplay, SYNC_VALUE_ZERO);
@ -347,6 +347,13 @@ meta_sync_new (Display *xdisplay)
return self;
}
static void
meta_sync_import (MetaSync *self)
{
g_return_if_fail (self->gl_x11_sync == 0);
self->gl_x11_sync = meta_gl_import_sync (GL_SYNC_X11_FENCE_EXT, self->xfence, 0);
}
static Bool
alarm_event_predicate (Display *dpy,
XEvent *event,
@ -437,6 +444,12 @@ meta_sync_ring_init (Display *xdisplay)
ring->syncs_array[i] = sync;
g_hash_table_replace (ring->alarm_to_sync, (gpointer) sync->xalarm, sync);
}
/* Since the connection we create the X fences on isn't the same as
* the one used for the GLX context, we need to XSync() here to
* ensure glImportSync() succeeds. */
XSync (xdisplay, False);
for (i = 0; i < NUM_SYNCS; ++i)
meta_sync_import (ring->syncs_array[i]);
ring->current_sync_idx = 0;
ring->current_sync = ring->syncs_array[0];