user manual

Buffer Swap Criteria

The criteria for buffer swaps involves when a window is ready to swap and

when a group is ready to swap.

Window Buffer Swaps

Any rendering surface that is not a window—such as a non-visible

rendering buffer—is always ready, otherwise the following criteria must be

satisﬁ ed before a buffer swap for a window can be performed:

The window itself must be ready, meaning:

A buffer swap command has been issued for it.

Its swap interval has elapsed.

If the window belongs to a group, all the windows in the group must

be ready.

If the window belongs to a group and that group is bound to a barrier,

all groups bound to that barrier must be ready.

Group and Barrier Buffer Swaps

Buffer swaps for all windows in a swap group take place concurrently

and buffer swaps for all groups using a barrier take place concurrently.

For barrier swaps, the vertical retraces of the screens of all the

groups must also be synchronized, otherwise there is no guarantee of

concurrency between groups.

An implementation may support a limited number of swap groups and

barriers and may have restrictions on where the users of a barrier can

reside.

For example, an implementation may allow the users to reside on

different display devices or even hosts. An implementation may

return zero for any of maxGroups and maxBarriers returned by

QueryMaxSwapGroupsNV if swap groups or barriers are not available

in that implementation or on that host.

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Using the OpenGL Extensions