And here's the Swap extension
The Swap Extension
Version 1.0
2013-2-14
Keith Packard
kei...@keithp.com
Intel Corporation
1. Introduction
The Swap extension provides GL SwapBuffers semantics to move pixels
From a pixmap to a drawable. This can be used by OpenGL
implementations or directly by regular applications.
1.1. Acknowledgments
Eric Anholt <e...@anholt.net>
Dave Airlie <airl...@redhat.com>
Kristian Høgsberg <k...@bitplanet.net>
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2. Data Types
The server side region support specified in the Xfixes extension
version 2 is used in the SwapRegion request.
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4. Errors
No errors are defined by the Swap extension.
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5. Events
The Swap extension provides a new event, SwapComplete, to signal when
a swap operation has finished.
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6. Protocol Types
SWAPSELECTMASK { SwapCompleteMask }
Used with SwapSelectInput to specify which events a client is
to receive.
SWAPIDLE {
pixmap: PIXMAP
valid: BOOL
swap-hi: CARD32
swap-lo: CARD32
}
This structure contains information about a pixmap which had
been used in a SwapRegion request and which the server is now
finished with. If valid is TRUE, swap-hi/swap-lo form a 64-bit
swap count value from the SwapRegion request which matches the
data that the pixmap currently contains. If valid is FALSE,
then the contents of the pixmap are undefined.
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7. Extension Initialization
The name of this extension is "Swap".
┌───
SwapQueryVersion
client-major-version: CARD32
client-minor-version: CARD32
▶
major-version: CARD32
minor-version: CARD32
└───
The client sends the highest supported version to the server
and the server sends the highest version it supports, but no
higher than the requested version. Major versions changes can
introduce incompatibilities in existing functionality, minor
version changes introduce only backward compatible changes.
It is the clients responsibility to ensure that the server
supports a version which is compatible with its expectations.
Backwards compatible changes included addition of new
requests.
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8. Extension Requests
┌───
SwapRegion
destination: DRAWABLE
region: REGION
src-off-x,src-off-y: INT16
source: PIXMAP
swap-interval: CARD32
target_msc_hi: CARD32
target_msc_lo: CARD32
divisor_hi: CARD32
divisor_lo: CARD32
remainder_hi: CARD32
remainder_lo: CARD32
▶
swap_hi: CARD32
swap_lo: CARD32
suggested-x-off,suggested-y-off: INT16
suggested-width,suggested-height: CARD16
idle: LISTofSWAPIDLE
└───
Errors: Pixmap, Drawable, Region, Value
Schedule a swap of the specified region from the source pixmap
to the destination drawable.
region specifies the region within the destination to be
swapped from the source.
src-off-x and src-off-y specify the offset to be added to
region to align it with the source pixmap.
swap-interval specifies the minimum number of frames since the
last SwapRegion request.
target_msc_hi/target_msc_lo form a 64-bit value marking the
target media stamp count for the swap request. When non-zero,
these mark the desired time where the data should be
presented.
divisor_hi/divisor_lo form a 64-bit value marking the desired
media stamp count interval between swaps.
remainder_hi/remainder_lo form a 64-bite value marking the
desired offset within the divisor_hi/divisor_lo swap interval.
In the reply, swap_hi/swap_lo form a 64-bit swap count value
when the swap will actually occur (e.g. the last queued swap
count + (pending swap count * swap interval)).
suggested-width and suggested-height offer a hint as to the
best pixmap size to use for full-sized swaps in the
future. suggested-x-off and suggested-y-off provide a hint as
to where the window contents should be placed within that
allocation for future swaps.
idle provides a list of pixmaps which were passed in previous
SwapRegion requests by this client targeting the same destination.
┌───
SwapSelectInput
drawable: DRAWABLE
mask: SETofSWAPSELECTMASK
└───
Errors: Drawable
Selects which Swap events are to be delivered to the
requesting client.
┌───
SwapGetMSC
drawable: DRAWABLE
▶
ust, msc, sbc: CARD64
└───
Errors: Window
Get the current media stamp counter (MSC) and swap buffer count (SBC)
along with the unadjusted system time (UST) when the MSC was last
incremented.
┌───
SwapWaitMSC
drawable: DRAWABLE
target_msc: two CARD32s
divisor: two CARD32s
remainder: two CARD32s
▶
ust, msc, sbc: CARD64
└───
Errors: Window
Blocks the client until either the frame count reaches target_msc or,
if the frame count is already greater than target_msc when the request
is received, until the frame count % divisor = remainder. If divisor
is 0, the client will be unblocked if the frame count is greater than
or equal to the target_msc.
Returns the current media stamp counter (MSC) and swap buffer count
(SBC) along with the unadjusted system time (UST) when the MSC was last
incremented.
┌───
SwapWaitSBC
drawable: DRAWABLE
target_sbc: two CARD32s
▶
ust, msc, sbc: CARD64
└───
Errors: Window
Blocks the client until the swap buffer count reaches target_sbc. If
the swap buffer count is already greater than or equal to target_sbc
when the request is recieved, this request will return immediately.
If target_sbc is 0, this request will block the client until all
previous DRI2SwapBuffers requests have completed.
Returns the current media stamp counter (MSC) and swap buffer count
(SBC) along with the unadjusted system time (UST) when the MSC was last
incremented.
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9. Extension Events
┌───
SwapComplete
▶
drawable: CARD32
ust: CARD64
msc: CARD64
sbc: CARD64
└───
This event is delivered when a SwapRegion operation
completes. Note that this may be later than when the
SwapRegion request is executed as the operation itself may be
delayed until the correct frame count has been reached.
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10. Extension Versioning
The Swap extension is adapted from pieces of the DRI2 extension
1.0: First published version
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11. Relationship with other extensions
As an extension designed to support other extensions, there is
naturally some interactions with other extensions.
11.1 GLX
GLX has no direct relation with Swap, but a direct rendering OpenGL
application may use GLX to discover
11.2 DRI3
DRI3 provides a mechanism for connecting direct rendering
applications with X pixmaps. Those pixmaps can then be used with Swap
to provide a complete direct rendering solution for OpenGL or other APIs.
11.3 DRI2
Swap provides similar functionality to the DRI2CopyRegion and
DRI2SwapBuffers requests, but uses regular X resources for both source
and destination pixel buffers instead of defining new resources.
Swap and DRI3 are designed in conjunction to replace DRI2
11.2 XvMC / Xv
We might add a DRI2_BUFFER_YUV to do vsynced colorspace conversion
blits.
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Appendix A. Protocol Encoding
Syntactic Conventions
This document uses the same syntactic conventions as the core X
protocol encoding document.
A.1 Common Types
┌───
SWAPIDLE
4 PIXMAP pixmap
1 BOOL valid
3 unused
4 CARD32 swap-hi
4 CARD32 swap-lo
└───
A.2 Protocol Requests
┌───
SwapQueryVersion
1 CARD8 major opcode
1 0 Swap opcode
2 3 length
4 CARD32 major version
4 CARD32 minor version
▶
1 1 Reply
1 unused
2 CARD16 sequence number
4 0 reply length
4 CARD32 major version
4 CARD32 minor version
16 unused
└───
┌───
SwapRegion
1 CARD8 major opcode
1 1 Swap opcode
2 11 length
4 DRAWABLE destination
4 REGION region
2 INT16 src-off-x
2 INT16 src-off-y
4 CARD32 swap-interval
4 CARD32 target_msc_hi
4 CARD32 target_msc_lo
4 CARD32 divisor_hi
4 CARD32 divisor_lo
4 CARD32 remainder_hi
4 CARD32 remainder_lo
▶
1 1 Reply
1 unused
2 CARD16 sequence number
4 4n reply length
4 CARD32 swap-hi
4 CARD32 swap-lo
2 INT16 suggested-x-off
2 INT16 suggested-y-off
2 CARD16 suggested-width
2 CARD16 suggested-height
8 unused
16n LISTofSWAPIDLE idle
└───
┌───
SwapGetMSC
1 CARD8 major opcode
1 9 Swap opcode
2 8 length
4 DRAWABLE drawable
▶
1 1 Reply
1 unused
2 CARD16 sequence number
4 0 reply length
4 CARD32 ust_hi
4 CARD32 ust_lo
4 CARD32 msc_hi
4 CARD32 msc_lo
4 CARD32 sbc_hi
4 CARD32 sbc_lo
└───
┌───
SwapWaitMSC
1 CARD8 major opcode
1 10 Swap opcode
2 8 length
4 DRAWABLE drawable
4 CARD32 target_msc_hi
4 CARD32 target_msc_lo
4 CARD32 divisor_hi
4 CARD32 divisor_lo
4 CARD32 remainder_hi
4 CARD32 remainder_lo
▶
1 1 Reply
1 unused
2 CARD16 sequence number
4 0 reply length
4 CARD32 ust_hi
4 CARD32 ust_lo
4 CARD32 msc_hi
4 CARD32 msc_lo
4 CARD32 sbc_hi
4 CARD32 sbc_lo
└───
┌───
SwapWaitSBC
1 CARD8 major opcode
1 11 Swap opcode
2 8 length
4 DRAWABLE drawable
4 CARD32 swap_hi
4 CARD32 swap_lo
▶
1 1 Reply
1 unused
2 CARD16 sequence number
4 0 reply length
4 CARD32 ust_hi
4 CARD32 ust_lo
4 CARD32 msc_hi
4 CARD32 msc_lo
4 CARD32 sbc_hi
4 CARD32 sbc_lo
└───
A.3 Protocol Events
The Swap extension specifies the SwapComplete event.
┌───
SwapComplete
1 CARD8 type
1 CARD8 extension
2 CARD16 sequenceNumber
4 DRAWABLE drawable
4 CARD32 ust_hi
4 CARD32 ust_lo
4 CARD32 msc_hi
4 CARD32 msc_lo
4 CARD32 sbc_hi
4 CARD32 sbc_lo
└───
A.4 Protocol Errors
The Swap extension specifies no errors.
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--
keith.pack...@intel.com
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