eglClientWaitSync — Wait in the client for a sync object to be signalled
EGLint eglClientWaitSync(
|
(EGLDisplay display, |
EGLSync sync, | |
EGLint flags, | |
EGLTime timeout) ; |
display
Specifies the EGL display connection.
sync
Specifies the sync object to wait on.
flags
Specifies flags controlling wait behavior.
timeout
Specifies wait timeout interval.
eglClientWaitSync
blocks the calling thread
until the specified sync object sync
is
signaled, or until timeout
nanoseconds
have passed.
More than one eglClientWaitSync
may be
outstanding on the same sync
at any given
time. When there are multiple threads blocked on the same
sync
and the sync object is signaled, all
such threads are released, but the order in which they are
released is not defined.
If the value of timeout
is zero, then
eglClientWaitSync
simply tests the current
status of sync
. If the value of
timeout
is the special value
EGL_FOREVER
, then
eglClientWaitSync
does not time out. For
all other values, timeout
is adjusted to
the closest value allowed by the implementation-dependent
timeout accuracy, which may be substantially longer than one
nanosecond.
eglClientWaitSync
returns one of three
status values describing the reason for returning. A return
value of EGL_TIMEOUT_EXPIRED
indicates that
the specified timeout period expired before
sync
was signaled, or if
timeout
is zero, indicates that
sync
is not signaled. A return value of
EGL_CONDITION_SATISFIED
indicates that
sync
was signaled before the timeout
expired, which includes the case when
sync
was already signaled when
eglClientWaitSync
was called. If an error
occurs then an error is generated and
EGL_FALSE
is returned.
If the sync object being blocked upon will not be signaled in
finite time (for example, by an associated fence command issued
previously, but not yet flushed to the graphics pipeline), then
eglClientWaitSync
may wait forever. To help
prevent this behavior, if the
EGL_SYNC_FLUSH_COMMANDS_BIT
bit is set in
flags
, and sync
is
unsignaled when eglClientWaitSync
is
called, then the equivalent of Flush() will be performed for the
current API context (i.e., the context returned by
eglGetCurrentContext
) before blocking on
sync
. If no context is current for the
bound API, the EGL_SYNC_FLUSH_COMMANDS_BIT
bit is ignored.
Note: the simple Flush behavior defined by
EGL_SYNC_FLUSH_COMMANDS_BIT
will not help
when waiting for a fence command issued in a different context's
command stream. Applications which block on a fence sync object
must take additional steps to ensure that the context from which
the associated fence command was issued has flushed that command
to the graphics pipeline.
eglClientWaitSync
returns
EGL_FALSE
on failure.
If sync
is not a valid sync object for
display
, an
EGL_BAD_PARAMETER
error is generated.
If display
does not match the
EGLDisplay passed to
eglCreateSync
when
sync
was created, the behaviour is
undefined.
eglClientWaitSync
is available only if the
EGL version is 1.5 or greater.
eglCreateSync,
eglGetCurrentContext,
eglWaitSync,
glFinish
,
vgFinish
Copyright © 2003-2014 The Khronos Group Inc. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.