kc3-lang/angle/extensions/EGL_ANGLE_sync_control_rate.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_ANGLE_sync_control_rate.txt

• Name
  
     ANGLE_sync_control_rate
  
  Name Strings
  
     EGL_ANGLE_sync_control_rate
  
  Contact
  
     Jonah Ryan-Davis, Google (jonahr 'at' google.com)
  
  Status
  
     Draft.
  
  Version
  
     Version 1, 2020-03-24
  
     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 eglGetMscRateANGLE(EGLDisplay* dpy,
                             EGLSurface surface,
                             int32_t* numerator,
                             int32_t* denominator)
  
  New Tokens
  
     None
  
  Additions to the EGL 1.3 Specification
  
     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.
  
     eglGetMscRateANGLE returns the rate at which the MSC will be incremented
     for the display associated with <hdc>. The rate is expressed in Hertz
     as <numerator> / <denominator>. If the MSC rate in Hertz is an
     integer, then <denominator> will be 1 and <numerator> will be
     the MSC rate.
  
     The function eglGetMscRateANGLE 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 eglGetMscRateANGLE will return FALSE if there is no
     current EGLContext.
  
  New Implementation Dependent State
  
     None
  
  Revision History
  
      Version 1, 2020-03-24 (Jonah Ryan-Davis)
         - Initial draft, based on GLX_OML_sync_control revision 6.0.
  

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