kc3-lang/angle/extensions/EGL_CHROMIUM_sync_control.txt

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• Hash : 4b94d7bb
  Author :
  Date : 2020-03-24T17:23:19
  

  Split EGL_CHROMIUM_sync_control into EGL_ANGLE_sync_control_rate
  
  eglGetMscRateCHROMIUM was added to EGL_CHROMIUM_sync_control based
  on the original extension GLX_OML_sync_control. However, this new
  function is not universally implemented. This CL moves it to a new
  extension, EGL_ANGLE_sync_control_rate, and renames it to
  eglGetMscRateANGLE.
  
  Bug: chromium:1064078
  Change-Id: Ia2a29c6776b2b2bf2b98e58ee83b5f141ed01301
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2118154
  Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
  Reviewed-by: Tim Van Patten <timvp@google.com>
  

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• extensions/EGL_CHROMIUM_sync_control.txt

• Name
  
     CHROMIUM_sync_control
  
  Name Strings
  
     EGL_CHROMIUM_sync_control
  
  Contact
  
     Stéphane Marchesin, Google (marcheu 'at' google.com)
  
  Status
  
     Draft.
  
  Version
  
     Version 2, 2015-05-05
  
     Based on GLX_OML_sync_control Revision 6.0
  
  Number
  
     ???
  
  Dependencies
  
     The extension is written against the EGL 1.2 Specification, although it
     should work on other versions of these specifications. This extension
     also requires an operating system which supports CLOCK_MONOTONIC.
  
  Overview
  
     This extension provides counters which let applications know about the
     timing of the last vertical retrace. By looking at the system clock, as
     well as the refresh rate of the monitor, this should enable applications
     to predict the position of future retraces so as to schedule an optimal
     workload.
  
     This extension incorporates the use of three counters that provide
     the necessary synchronization. The Unadjusted System Time (or UST)
     is the 64-bit CLOCK_MONOTONIC clock; in particular this lets the
     application schedule future vertical retraces by querying this clock.
     The graphics Media Stream Counter (or graphics MSC) is a counter
     that is unique to the graphics subsystem and increments for each
     vertical retrace that occurs. The Swap Buffer Counter (SBC) is an
     attribute of an EGLSurface and is incremented each time a swap
     buffer action is performed on the associated surface.
  
     The use of these three counters allows the application to
     synchronize graphics rendering to vertical retraces and/or swap
     buffer actions. For example, by querying the synchronization values for
     a given surface, the application can accurately predict the timing for
     the next vertical retraces and schedule rendering accordingly.
  
  Issues
  
     None.
  
  IP Status
  
     No known issues.
  
  New Procedures and Functions
  
     Bool eglGetSyncValuesCHROMIUM(EGLDisplay dpy,
                                   EGLSurface surface,
                                   int64_t* ust,
                                   int64_t* msc,
                                   int64_t* sbc)
  
  New Tokens
  
     None
  
  Additions to the EGL 1.3 Specification
  
     eglGetSyncValuesCHROMIUM returns the current UST/MSC/SBC triple. A UST
     timestamp is obtained each time the graphics MSC is incremented.
     If this value does not reflect the value of the UST at the time the
     first scan line of the display begins passing through the video
     output port, it will be adjusted by the graphics driver to do so
     prior to being returned by any of the functions defined by this
     extension.
  
     This UST timestamp, together with the current graphics MSC and the
     current SBC, comprise the current UST/MSC/SBC triple. The UST,
     graphics MSC, and SBC values are not part of the render context
     state. These values cannot be pushed or popped. The graphics MSC
     value is initialized to 0 when the graphics device is initialized.
     The SBC is per-surface state and is initialized to 0 when the
     EGLSurface data structure is initialized.
  
     The SBC value is incremented by the graphics driver at the completion
     of each buffer swap (e.g., the pixel copy has been completed or the
     hardware register that swaps memory banks has been written). For pixel
     formats that do not contain a back buffer, the SBC will always be
     returned as 0.
  
     The graphics MSC value is incremented once for each screen refresh.
     For a non-interlaced display, this means that the graphics MSC value
     is incremented for each frame. For an interlaced display, it means
     that it will be incremented for each field. For a multi-monitor
     system, the monitor used to determine MSC is the one where the surface
     is located. If the surface spans multiple monitors, the monitor used
     to determine MSC is the one with the biggest coverage in pixels.
  
     The function eglGetSyncValuesCHROMIUM will return TRUE if the function
     completed successfully, FALSE otherwise.
  
     Each time eglSwapBuffer succeeds, the SBC will be increased within a
     finite time period.
  
  Errors
  
     The function eglGetSyncValuesCHROMIUM will return FALSE if there is no
     current EGLContext.
  
  
  New State
  
     Get Value                 Get Command            Type    Initial Value
     ---------                 -----------            ----    -------------
       [UST]             eglGetSyncValuesCHROMIUM      Z      unspecified
       [MSC]             eglGetSyncValuesCHROMIUM      Z                  0
       [SBC]             eglGetSyncValuesCHROMIUM      Z                  0
  
  New Implementation Dependent State
  
     None
  
  Revision History
  
      Version 2, 2015-05-05 (Chad Versace)
         - Rename to EGL_CHROMIUM_sync_control from EGL_CHROMIUM_get_sync_values.
           EGL_CHROMIUM_sync_control is the de facto extension name because all
           users query that extension string.
  
      Version 1, 2014-08-15 (Stéphane Marchesin)
         - Initial draft, based on GLX_OML_sync_control revision 6.0.
  

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