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diff --git a/presentproto.txt b/presentproto.txt new file mode 100644 index 0000000..fdaf658 --- /dev/null +++ b/presentproto.txt @@ -0,0 +1,787 @@ + The Present Extension + Version 1.0 + 2013-6-6 + + Keith Packard + keithp@keithp.com + Intel Corporation + +1. Introduction + +The Present extension provides a way for applications to update their +window contents from a pixmap in a well defined fashion, synchronizing +with the display refresh and potentially using a more efficient +mechanism than copying the contents of the source pixmap. + +1.1. Future Present extension versions + +This document includes speculation about future 'redirect' support +within the Present extension. All such information is subject to +change and is provided only as an aid to further Present development. + +1.2. Acknowledgments + +Eric Anholt <eric@anholt.net> +Owen Taylor <otaylor@redhat.com> +James Jones <jajones@nvidia.com> + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + +2. Data Types + +PRESENTEVENTID { XID } + + Defines a unique event delivery target for Present + events. Multiple event IDs can be allocated to provide + multiple distinct event delivery contexts. + +PRESENTNOTIFY { + window: WINDOW + serial: CARD32 + } + + A list of these is passed to PresentPixmap; when the indicated + PresentPixmap completes, PresentCompletNotify events will be + delivered both to the PresentPixmap window/serial parameter as + well as each of the entries in the list of PRESENTNOTIFY parameter. + +PRESENTEVENTTYPE { PresentConfigureNotify, + PresentCompleteNotify, + PresentIdleNotify } + +PRESENTEVENTMASK { PresentConfigureNotifyMask, + PresentCompleteNotifyMask, + PresentIdleNotifyMask } + +PRESENTOPTION { PresentOptionAsync, + PresentOptionCopy, + PresentOptionUST } + +PRESENTCAPABILITY { PresentCapabilityAsync, + PresentCapabilityFence, + PresentCapabilityUST } + +PRESENTCOMPLETEKIND { PresentCompleteKindPixmap, + PresentCompleteKindMSCNotify } + +PRESENTCOMPLETEMODE { PresentCompleteModeCopy, + PresentCompleteModeFlip, + PresentCompleteModeSkip } + +The Present extension also uses the Sync extension Fence data type to +provide synchronization for pixmaps. + +2.1. Data Types proposed for a later Present extension version + +PRESENTEVENTTYPE { ... + PresentRedirectNotify } + +PRESENTEVENTMASK { ... + PresentSubredirectNotifyMask } + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + +3. Errors + +EventID + A value for an EventID argument does not name a defined EventID + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + +5. Events + +ConfigureNotify events inform clients about window configuration +changes which can affect the allocation of window-related buffers. + +CompleteNotify events inform clients about the completion of a pending +PresentPixmap request. + +IdleNotify events inform clients when pixmaps are available for re-use. + +5.1. Events proposed for a later Present extension version + +RedirectNotify events inform clients about other clients PresentPixmap +requests. + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + +6. Extension Initialization + +The name of this extension is "Present" + +┌─── + PresentQueryVersion + 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. + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + +7. Extension Requests + +┌─── + PresentPixmap + window: WINDOW + pixmap: PIXMAP + serial: CARD32 + valid-area: REGION or None + update-area: REGION or None + x-off, y-off: INT16 + target-crtc: CRTC or None + wait-fence: FENCE + idle-fence: FENCE + options: SETofPRESENTOPTION + target-msc: CARD64 + divisor: CARD64 + remainder: CARD64 + notifies: LISTofPRESENTNOTIFY +└─── + Errors: Window, Pixmap, Match + + Provides new content for the specified window, to be made + visible at the specified time (defined by 'target-msc', 'divisor' + and 'remainder'). If the depth of 'pixmap' and 'window' do not + match, a Match error will be generated. + + 'serial' is an arbitrary client-specified value which will + be returned in the associated PresentCompleteNotify event so + that the client can associate the event and request. + + 'valid-area' defines the portion of 'pixmap' which contains + valid window contents, or None if the pixmap contains valid + contents for the whole window. + + 'update-area' defines the subset of the window to be updated, + or None if the whole window is to be updated. + + PresentPixmap may use any region of 'pixmap' which contains + 'update-area' and which is contained by 'valid-area'. In other + words, areas inside 'update-area' will be presented from + 'pixmap', areas outside 'valid-area' will not be presented + from 'pixmap' and areas inside 'valid-area' but outside + 'update-area' may or may not be presented at the discretion of + the X server. + + 'x-off' and 'y-off' define the location in the window where + the 0,0 location of the pixmap will be presented. valid-area + and update-area are relative to the pixmap. + + PresentPixmap will block until 'wait-fence' is triggered. + + When the X server has finished using 'pixmap' for this + operation, it will send a PresentIdleNotify event and arrange + for any 'idle-fence' to be triggered. This may be at any time + following the PresentPixmap request -- the contents may be + immediately copied to another buffer, copied just in time for + the vblank interrupt or the pixmap may be used directly for + display (in which case it will be busy until some future + PresentPixmap operation). + + If 'idle-fence' is not None, then the client guarantees to the + X server that it will wait for that fence to be signalled + before it uses the pixmap again. If 'idle-fence' is None, then + the X server must arrange for the pixmap to be re-usable by + the client as soon as the PresentIdleNotify event has been + received. Note that if PresentCapabilityFence is set for the + associated CRTC, then clients should use fences to improve + overall systme performance. If PresentCapabilityFence is not + set, then using fences offers no benefit, but also no cost. + + If 'target-msc' is greater than the current msc for 'window', + the presentation will occur at (or after) the 'target-msc' + field. Otherwise, the presentation will occur after the next + field where msc % 'divisor' == 'remainder'. + + If 'target-crtc' is None, then the X server will choose a + suitable CRTC for synchronization. + + If 'options' contains PresentOptionAsync, and the 'target-msc' + is less than or equal to the current msc for 'window', then + the operation will be performed as soon as possible, not + necessarily waiting for the next vertical blank interval. + + If 'options' contains PresentOptionCopy, then 'pixmap' will be + idle, and 'idle-fence' triggered as soon as the operation occurs. + + If 'options' contains PresentOptionUST, then target-msc, + divisor and remainder will all be interpreted as UST values + instead of MSC values and the frame update will be scheduled + for the specified UST time, If the target-crtc supports + PresentCapabilityUST, then the swap time will be as close to + the target time as the driver can manage. Otherwise, the + server will take the target UST time and convert it to a + suitable target MSC value. + + After the presentation occurs, a PresentCompleteNotify event + with kind PresentCompleteKindPixmap will be generated, both to + 'window' as well as all members of 'notifies'. + + If 'window' is destroyed before the presentation occurs, then + the presentation action will not be completed. + + PresentPixmap holds a reference to 'pixmap' until the + presentation occurs, so 'pixmap' may be immediately freed + after the request executes, even if that is before the + presentation occurs. + + If 'idle-fence' is destroyed before the presentation occurs, + then idle-fence will not be signaled but the presentation will + occur normally. + + If 'wait-fence' is destroyed before it becomes triggered, then + the presentation operation will no longer wait for it and will + occur when the other conditions are satisfied. + +┌─── + PresentNotifyMSC + window: WINDOW + serial: CARD32 + target-msc: CARD64 + divisor: CARD64 + remainder: CARD64 +└─── + Errors: Window + + Delivers a PresentCompleteNotifyEvent with kind + PresentCompleteKindNotifyMSC after the time specified by + 'target-msc', 'divisor' and 'remainder'). + + 'serial' is an arbitrary client-specified value which will be + returned in the event so that the client can associate the + event and request. + + If 'target-msc' is greater than the current msc for 'window', + the event will be delivered at (or after) the 'target-msc' + field. Otherwise, the event delivery will occur after the next + field where msc % 'divisor' == 'remainder'. + + If 'window' is destroyed before the event is delivered, then + the event delivery will not be completed. + +┌─── + PresentSelectInput + event-id: PRESENTEVENTID + window: WINDOW + eventMask: SETofPRESENTEVENT +└─── + Errors: Window, Value, Match, IDchoice, Access + + Selects the set of Present events to be delivered for the + specified window and event context. PresentSelectInput can + create, modify, or delete event contexts. An event context is + associated with a specific window; using an existing event + context with a different window generates a Match error. + + If eventContext specifies an existing event context, then if + eventMask is empty, PresentSelectInput deletes the specified + context, otherwise the specified event context is changed to + select a different set of events. + + If eventContext is an unused XID, then if eventMask is empty + no operation is performed. Otherwise, a new event context is + created selecting the specified events. + +┌─── + PresentQueryCapabilities + target: CRTC or WINDOW + ▶ + capabilities: SETofPRESENTCAPABILITY +└─── + Errors: Window, CRTC + + Returns the supported capabilities for the target CRTC. If + 'target' is a CRTC, then it is used as the target CRTC. If + 'target' is a WINDOW, then the target CRTC is selected by the + X server from among the CRTCs on the screen specified by the window. + + PresentCapabilityAsync means that the target device can flip + the scanout buffer mid-frame instead of waiting for a vertical + blank interval. The precise latency between the flip request + and the actual scanout transition is not defined by this + specification, but is intended to be no more than a few + scanlines. + + PresentCapabilityFence means that the target device can take + advantage of SyncFences in the Present operations to improve + GPU throughput. The driver must operate correctly in the + absense of fences, but may have reduced performance. Using + fences for drivers not advertising this capability should have + no performance impact. + + PresentCapabilityUST means that the target device can scanout + the image at an arbitrary UST time value, and is not driven by + a periodic scanout timer. Applications specifying UST times + for PresentPixmap can expect that their image will appear to + the user within a short amount of time from that specified in + the request. The precise accuracy of the scanout time is not + defined by the extension, but is expected to be on the order + of milliseconds or less. + + +7.1 Requests proposed for a later Present extension version + + These are not part of the standard and represent future plans + for the Present extension. + +┌─── + PresentSelectInput + ... +└─── + ... + + Specifying PresentSubredirectNotify Mask causes PresentPixmap + requests on any child of 'window' from other clients to + generate PresentRedirectNotify events to 'window' instead of + actually performing the operation. However, only one client at + a time can select for PresentRedirect on a window. An attempt + to violate this restriction results in an Access error. + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + +8. Extension Events + +┌─── + PresentConfigureNotify + type: CARD8 XGE event type (35) + extension: CARD8 Present extension request number + sequence-number: CARD16 + length: CARD32 2 + evtype: CARD16 Present_ConfigureNotify + eventID: PRESENTEVENTID + window: WINDOW + x: INT16 + y: INT16 + width: CARD16 + height: CARD16 + off_x: INT16 + off_y: INT16 + pixmap_width: CARD16 + pixmap_height: CARD16 + pixmap_flags: CARD32 +└─── + + PresentConfigureNotify events are sent when the window + configuration changes if PresentSelectInput has requested + it. PresentConfigureNotify events are XGE events and so do not + have a unique event type. + + 'x' and 'y' are the parent-relative location of 'window'. + +┌─── + PresentCompleteNotify + type: CARD8 XGE event type (35) + extension: CARD8 Present extension request number + sequence-number: CARD16 + length: CARD32 2 + evtype: PRESENTEVENTTYPE PresentCompleteNotify + eventID: PRESENTEVENTID + window: WINDOW + kind: PRESENTCOMPLETEKIND + mode: PRESENTCOMPLETEMODE + serial: CARD32 + ust: CARD64 + msc: CARD64 +└─── + + CompleteNotify events are delivered when a PresentPixmap or + PresentNotifyMSC operation has completed. + + 'kind' is PresentCompleteKindPixmap when generated by a + PresentPixmap operation completion or + PresentCompleteKindNotifyMsc when generated by a + PresentNotifyMSC operation completion. + + 'mode' is PresentCompleteModeCopy when the source pixmap + contents are taken from the pixmap and the pixmap is idle + immediately after the presentation completes. 'mode' is + PresentCompleteModeFlip when the pixmap remains in-use even + after the presentation completes. It will become idle no later + than when the next PresentPixmap operation targeting the same + window by any client completes. If the presentation operation + was skipped because some later operation made it irrelevant, + then 'mode' will be PresentCompleteModeSkip. + + 'serial' is the value provided in the generating PresentPixmap + request. + + 'msc' and 'ust' indicate the frame count and system time when + the presentation actually occurred. + +┌─── + PresentIdleNotify + type: CARD8 XGE event type (35) + extension: CARD8 Present extension request number + sequence-number: CARD16 + length: CARD32 0 + evtype: PRESENTEVENTTYPE PresentIdleNotify + eventID: PRESENTEVENTID + window: WINDOW + serial: CARD32 + pixmap: PIXMAP + idle-fence: FENCE +└─── + + IdleNotify events are delivered when a pixmap used in a + PresentPixmap operation may be re-used by the client. + + 'window' is the window from the PresentPixmap to which this + event is delivered. + + 'serial' is the value provided in the associated PresentPixmap + request. + + 'pixmap' is the pixmap which is ready for re-use. + + 'idle-fence' is the fence which was provided in the + originating PresentPixmap request and is used to synchronize + rendering between the client and the X server's use of the + buffer. If not None, then the client must wait for the fence + to be signaled before using the pixmap. + +8.1. Extension Events proposed for a later Present extension version + +┌─── + PresentRedirectNotify + type: CARD8 XGE event type (35) + extension: CARD8 Present extension request number + sequence-number: CARD16 + length: CARD32 17 + 2 n + evtype: CARD16 Present_RedirectNotify + update-window: BOOL + + eventID: PRESENTEVENTID + event-window: WINDOW + window: WINDOW + pixmap: PIXMAP + serial: CARD32 + + valid-area: REGION + update-area: REGION + valid-rect: RECTANGLE + update-rect: RECTANGLE + x-off, y-off: INT16 + target-crtc: CRTC + wait-fence: FENCE + idle-fence: FENCE + options: SETofPRESENTOPTION + target-msc: CARD64 + divisor: CARD64 + remainder: CARD64 + notifies: LISTofPRESENTNOTIFY +└─── + + RedirectNotify events are delivered when the client has + selected for SubredirectNotify the parent of the target + window. All of the values provided to the PresentPixmap + request are provided. If the client simply passes these + parameters back to the X server, the effect will be as if the + original client executed the request. + + If 'update-window' is TRUE, then there are clients who have + requested composite automatic redirect on the window and who + presumably expect the window buffer to eventually contain + the application provided contents. The compositing manager + should at least occasionally update the window buffer with + suitable contents. The precise update interval is left to the + discretion of the client receiving this event. + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + +9. Extension Versioning + + 1.0: First published version + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + + +10. Relationship with other extensions + +As an extension designed to support other extensions, there is +naturally some interactions with other extensions. + +10.1 GLX + +GLX is both an application interface and an X extension. OpenGL +applications using the GLX API will use the GLX extension and may use +the Present extension to display application contents. + +10.2 DRI3 + +The DRI3 extension provides a way to share direct rendered pixel data +with the X server as X pixmaps. When used in conjunction with Present, +they provide a complete direct rendering solution for OpenGL or other +APIs. + +10.3 DRI2 + +Present provides similar functionality to the DRI2SwapBuffers and +requests, however Present uses X pixmaps to refer to the new window +contents instead of the DRI2 buffer attachments. + +Present and DRI3 are designed in conjunction to replace DRI2 + +10.4 XvMC / Xv + +It might be nice to be able to use YUV formatted objects as Present +sources. + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ + +Appendix A. Protocol Encoding + +Syntactic Conventions + +This document uses the same syntactic conventions as the core X +protocol encoding document. + + +A.1 Common Types +┌─── + PresentEventType + 0 PresentConfigureNotify + 1 PresentCompleteNotify + 2 PresentIdleNotify +└─── + +┌─── + PresentEventMask + 1 PresentConfigureNotifyMask + 2 PresentCompleteNotifyMask + 4 PresentIdleNotifyMask +└─── + +┌─── + PresentOption + 1 PresentOptionAsync + 2 PresentOptionCopy; + 4 PresentOptionUST +└─── + +┌─── + PresentCapability + 1 PresentCapabilityAsync + 2 PresentCapabilityFence + 4 PresentCapabilityUST +└─── + +┌─── + PresentCompleteKind + 0 PresentCompleteKindPixmap + 1 PresentCompleteKindMSCNotify +└─── + +┌─── + PresentCompleteMode + 0 PresentCompleteModeCopy + 1 PresentCompleteModeFlip + 2 PresentCompleteModeSkip +└─── + +┌─── + PresentNotify + 4 Window window + 4 CARD32 serial +└─── + +A.1.1 Common Types proposed for a later Present extension version + +┌─── + PresentEventType + ... + 3 PresentRedirectNotify +└─── + +┌─── + PresentEventMask + ... + 8 PresentSubredirectNotifyMask +└─── + +A.2 Protocol Requests + +┌─── + PresentQueryVersion + 1 CARD8 major opcode + 1 0 Present 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 +└─── + +┌─── + PresentPixmap + 1 CARD8 major opcode + 1 1 Present opcode + 2 18+2n length + 4 Window window + 4 Pixmap pixmap + 4 CARD32 serial + 4 Region valid-area + 4 Region update-area + 2 INT16 x-off + 2 INT16 y-off + 4 CRTC target-crtc + 4 SyncFence wait-fence + 4 SyncFence idle-fence + 4 CARD32 options + 4 unused + 8 CARD64 target-msc + 8 CARD64 divisor + 8 CARD64 remainder + 8n LISTofPresentNotify notifies +└─── + +┌─── + PresentNotifyMSC + 1 CARD8 major opcode + 1 2 Present opcode + 2 10 length + 4 Window window + 4 CARD32 serial + 4 unused + 8 CARD64 target-msc + 8 CARD64 divisor + 8 CARD64 remainder +└─── + +┌─── + PresentSelectInput + 1 CARD8 major opcode + 1 3 Present opcode + 2 4 length + 4 EventID event-id + 4 Window window + 4 SETofPRESENTEVENTMASK event-mask +└─── + +┌─── + PresentQueryCapabilities + 1 CARD8 major opcode + 1 4 Present opcode + 2 2 length + 4 CRTC or Window target + ▶ + 1 1 Reply + 1 unused + 2 CARD16 sequence number + 4 0 reply length + 4 SETofPRESENTCAPABILITY capabilities +└─── + +A.3 Protocol Events + +┌─── + PresentConfigureNotify + 1 35 XGE + 1 CARD8 Present extension opcode + 2 CARD16 sequence number + 4 2 length + 2 0 PresentConfigureNotify + 2 unused + 4 CARD32 event id + 4 Window window + 2 INT16 x + 2 INT16 y + 2 CARD16 width + 2 CARD16 height + 2 INT16 off x + 2 INT16 off y + + 2 CARD16 pixmap width + 2 CARD16 pixmap height + 4 CARD32 pixmap flags +└─── + +┌─── + PresentCompleteNotify + 1 35 XGE + 1 CARD8 Present extension opcode + 2 CARD16 sequence number + 4 2 length + 2 1 PresentCompleteNotify + 1 CARD8 kind + 1 CARD8 mode + 4 CARD32 event id + 4 Window window + 4 CARD32 serial + 8 CARD64 ust + + 8 CARD64 msc +└─── + +┌─── + PresentIdleNotify + 1 35 XGE + 1 CARD8 Present extension opcode + 2 CARD16 sequence number + 4 0 length + 2 2 PresentIdleNotify + 2 unused + 4 CARD32 event id + 4 Window window + 4 CARD32 serial + 4 Pixmap pixmap + 4 SyncFence idle-fence +└─── + +A.3.1 Protocol Events proposed for later Present extension version + +┌─── + PresentRedirectNotify + 1 35 XGE + 1 CARD8 Present extension opcode + 2 CARD16 sequence number + 4 18+2n length + 2 3 PresentRedirectNotify + 1 BOOL update-window + 1 unused + 4 CARD32 event id + 4 Window event-window + 4 Window window + 4 Pixmap pixmap + 4 CARD32 serial + + 4 Region valid-area + 4 Region update-area + 8 Rectangle valid-rect + 8 Rectangle update-rect + 2 INT16 x-off + 2 INT16 y-off + 4 CRTC target-crtc + 4 SyncFence wait-fence + 4 SyncFence idle-fence + 4 CARD32 options + 4 unused + 8 CARD64 target-msc + 8 CARD64 divisor + 8 CARD64 remainder + 8n LISTofPRESENTNOTIFY notifies +└─── + +A.4 Protocol Errors + +The Present extension defines no errors. + + ❄ ❄ ❄ ❄ ❄ ❄ ❄ |