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kc3-lang/angle/extensions/EGL_CHROMIUM_sync_control.txt
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Author :
Jonah Ryan-Davis
Date : 2020-01-23 13:57:21
Hash : 1a1a1427
Message : Expose eglGetMscRateCHROMIUM from EGL_CHROMIUM_sync_control When ANGLE is using the GL backend on GLX, we can expose eglGetMscRateCHROMIUM via glXGetMscRateOML. Otherwise, this function should return false. Bug: chromium:1042393 Change-Id: Id9b308c2217e07ee9860e2869be0e23b7a0c7411 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2017048 Commit-Queue: Jonah Ryan-Davis <jonahr@google.com> Reviewed-by: Geoff Lang <geofflang@chromium.org>
- extensions/EGL_CHROMIUM_sync_control.txt
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Name CHROMIUM_sync_control Name Strings EGL_CHROMIUM_sync_control Contact Stéphane Marchesin, Google (marcheu 'at' google.com) Status Draft. Version Version 3, 2020-01-23 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) Bool eglGetMscRateCHROMIUM(EGLDisplay* dpy, EGLSurface surface, int32_t* numerator, int32_t* denominator) 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. eglGetMscRateCHROMIUM 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 functions eglGetSyncValuesCHROMIUM, and eglGetMscRateCHROMIUM 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 functions eglGetSyncValuesCHROMIUM, and eglGetMscRateCHROMIUM 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 3, 2020-01-23 (Jonah Ryan-Davis) - Add the function eglGetMscRateCHROMIUM based on glXGetMscRateOML from GLX_OML_sync_control revision 6.0. 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.