docs/_extra/specs/EGL_MESA_platform_surfaceless.txt

Name

    MESA_platform_surfaceless

Name Strings

    EGL_MESA_platform_surfaceless

Contributors

    Chad Versace <chadversary@google.com>
    Haixia Shi <hshi@google.com>
    Stéphane Marchesin <marcheu@google.com>
    Zach Reizner <zachr@chromium.org>
    Gurchetan Singh <gurchetansingh@google.com>

Contacts

    Chad Versace <chadversary@google.com>

Status

    DRAFT

Version

    Version 2, 2016-10-13

Number

    EGL Extension #TODO

Extension Type

    EGL client extension

Dependencies

    Requires EGL 1.5 or later; or EGL 1.4 with EGL_EXT_platform_base.

    This extension is written against the EGL 1.5 Specification (draft
    20140122).

    This extension interacts with EGL_EXT_platform_base as follows. If the
    implementation supports EGL_EXT_platform_base, then text regarding
    eglGetPlatformDisplay applies also to eglGetPlatformDisplayEXT;
    eglCreatePlatformWindowSurface to eglCreatePlatformWindowSurfaceEXT; and
    eglCreatePlatformPixmapSurface to eglCreatePlatformPixmapSurfaceEXT.

Overview

    This extension defines a new EGL platform, the "surfaceless" platform. This
    platfom's defining property is that it has no native surfaces, and hence
    neither eglCreatePlatformWindowSurface nor eglCreatePlatformPixmapSurface
    can be used. The platform is independent of any native window system.

    The platform's intended use case is for enabling OpenGL and OpenGL ES
    applications on systems where no window system exists. However, the
    platform's permitted usage is not restricted to this case.  Since the
    platform is independent of any native window system, it may also be used on
    systems where a window system is present.

New Types

    None

New Procedures and Functions

    None

New Tokens

    Accepted as the <platform> argument of eglGetPlatformDisplay:

        EGL_PLATFORM_SURFACELESS_MESA           0x31DD

Additions to the EGL Specification

    None.

New Behavior

    To determine if the EGL implementation supports this extension, clients
    should query the EGL_EXTENSIONS string of EGL_NO_DISPLAY.

    To obtain an EGLDisplay on the surfaceless platform, call
    eglGetPlatformDisplay with <platform> set to EGL_PLATFORM_SURFACELESS_MESA.
    The <native_display> parameter must be EGL_DEFAULT_DISPLAY.

    eglCreatePlatformWindowSurface fails when called with a <display> that
    belongs to the surfaceless platform. It returns EGL_NO_SURFACE and
    generates EGL_BAD_NATIVE_WINDOW. The justification for this unconditional
    failure is that the surfaceless platform has no native windows, and
    therefore the <native_window> parameter is always invalid.

    Likewise, eglCreatePlatformPixmapSurface also fails when called with a
    <display> that belongs to the surfaceless platform.  It returns
    EGL_NO_SURFACE and generates EGL_BAD_NATIVE_PIXMAP.

    The surfaceless platform imposes no platform-specific restrictions on the
    creation of pbuffers, as eglCreatePbufferSurface has no native surface
    parameter.  Specifically, if the EGLDisplay advertises an EGLConfig whose
    EGL_SURFACE_TYPE attribute contains EGL_PBUFFER_BIT, then the EGLDisplay
    permits the creation of pbuffers with that config.

Issues

    None.

Revision History

    Version 2, 2016-10-13 (Chad Versace)
        - Assign enum values
        - Define interfactions with EGL 1.4 and EGL_EXT_platform_base.
        - Add Gurchetan as contributor, as he implemented the pbuffer support.

    Version 1, 2016-09-23 (Chad Versace)
        - Initial version
        - Posted for review at
          https://lists.freedesktop.org/archives/mesa-dev/2016-September/129549.html