extension.xml - mozsearch

<?xml version="1.0"?>

<extension href="WEBGL_compressed_texture_etc/">

  <name>WEBGL_compressed_texture_etc</name>

  <contact>

    <a href="https://www.khronos.org/webgl/public-mailing-list/">WebGL working group</a> (public_webgl 'at' khronos.org)

  </contact>

  <contributors>

    <contributor>Jeff Gilbert, Mozilla</contributor>

    <contributor>Members of the WebGL working group</contributor>

  </contributors>

  <number>29</number>

  <depends>

    <api version="1.0"/>

  </depends>

  <overview>

<p>

      This extension exposes the compressed texture formats defined as core in the

      <a href="http://www.khronos.org/registry/gles/specs/3.0/es_spec_3.0.4.pdf">

      OpenGL ES 3.0</a> spec to WebGL. These include the ETC2 and EAC formats, where

      ETC2 is a superset of ETC1. ETC1 textures can be loaded using the ETC2 token

      value. All of these formats are in the ETC family.

    </p>

<p>

      Browsers should not advertise this extension when the WebGL implementation, or

      graphics driver, supports these formats by decompressing them.

    </p>

    <features>

      <feature>

        Compression formats <code>COMPRESSED_R11_EAC</code>,

        <code>COMPRESSED_SIGNED_R11_EAC</code>,

        <code>COMPRESSED_RG11_EAC</code>,

        <code>COMPRESSED_SIGNED_RG11_EAC</code>,

        <code>COMPRESSED_RGB8_ETC2</code>,

        <code>COMPRESSED_SRGB8_ETC2</code>,

        <code>COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2</code>,

        <code>COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2</code>,

        <code>COMPRESSED_RGBA8_ETC2_EAC</code>,

        and <code>COMPRESSED_SRGB8_ALPHA8_ETC2_EAC</code> may be passed to the

        <code>compressedTexImage2D</code> and <code>compressedTexSubImage2D</code> entry points. In

        WebGL 2.0, they may also be passed to the <code>compressedTexImage3D</code> and

        <code>compressedTexSubImage3D</code> entry points with the <code>TEXTURE_2D_ARRAY</code>

        target.

      </feature>

      <feature>

        Calling <code>getParameter</code> with the argument <code>COMPRESSED_TEXTURE_FORMATS</code>

        will include the formats from this specification.

      </feature>

      <feature>

        For all of the formats, <code>validatedSize</code> (defined for each specific format

        below) is validated in the following ways:

        <ul>

            <li>

                <b>WebGL 1.0 and 2.0</b>: if the variant of <code>compressedTexImage*D</code> or

                <code>compressedTexSubImage*D</code> taking <code>ArrayBufferView pixels</code> is

                called, then the <code>byteLength</code> of the view must be equal to

                <code>validatedSize</code>, or an INVALID_VALUE error is generated.

            </li>

            <li>

                <b>WebGL 2.0</b>: if the variant of <code>compressedTexImage*D</code> or

                <code>compressedTexSubImage*D</code> taking <code>GLintptr offset</code> is called,

                and <code>offset + validatedSize</code> is greater than the size of the bound

                <code>PIXEL_UNPACK_BUFFER</code>, an <code>INVALID_OPERATION</code> error is

                generated.

            </li>

        </ul>

        <dl>

          <dt>COMPRESSED_R11_EAC</dt>

          <dt>COMPRESSED_SIGNED_R11_EAC</dt>

          <dt>COMPRESSED_RGB8_ETC2</dt>

          <dt>COMPRESSED_SRGB8_ETC2</dt>

          <dt>COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2</dt>

          <dt>COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2</dt>

          <dd><p><code>validatedSize</code> is computed in the following way:</p>

          <blockquote><code>

            floor((width + 3) / 4) * floor((height + 3) / 4) * 8

          </code></blockquote>

          </dd>

        </dl>

        <dl>

          <dt>COMPRESSED_RG11_EAC</dt>

          <dt>COMPRESSED_SIGNED_RG11_EAC</dt>

          <dt>COMPRESSED_RGBA8_ETC2_EAC</dt>

          <dt>COMPRESSED_SRGB8_ALPHA8_ETC2_EAC</dt>

          <dd><p><code>validatedSize</code> is computed in the following way:</p>

          <blockquote><code>

            floor((width + 3) / 4) * floor((height + 3) / 4) * 16

          </code></blockquote>

          </dd>

        </dl>

      </feature>

    </features>

  </overview>

  <idl xml:space="preserve">

[NoInterfaceObject]

interface WEBGL_compressed_texture_etc {

    /* Compressed Texture Formats */

    const GLenum COMPRESSED_R11_EAC                        = 0x9270;

    const GLenum COMPRESSED_SIGNED_R11_EAC                 = 0x9271;

    const GLenum COMPRESSED_RG11_EAC                       = 0x9272;

    const GLenum COMPRESSED_SIGNED_RG11_EAC                = 0x9273;

    const GLenum COMPRESSED_RGB8_ETC2                      = 0x9274;

    const GLenum COMPRESSED_SRGB8_ETC2                     = 0x9275;

    const GLenum COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2  = 0x9276;

    const GLenum COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2 = 0x9277;

    const GLenum COMPRESSED_RGBA8_ETC2_EAC                 = 0x9278;

    const GLenum COMPRESSED_SRGB8_ALPHA8_ETC2_EAC          = 0x9279;

};

  </idl>

  <newtok>

    <function name="compressedTexImage2D">

      <param name="internalformat" type="GLenum"/>

      Accepted by the <code>internalformat</code> parameter:

      <code>COMPRESSED_R11_EAC</code>,

      <code>COMPRESSED_SIGNED_R11_EAC</code>,

      <code>COMPRESSED_RG11_EAC</code>,

      <code>COMPRESSED_SIGNED_RG11_EAC</code>,

      <code>COMPRESSED_RGB8_ETC2</code>,

      <code>COMPRESSED_SRGB8_ETC2</code>,

      <code>COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2</code>,

      <code>COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2</code>,

      <code>COMPRESSED_RGBA8_ETC2_EAC</code> or

      <code>COMPRESSED_SRGB8_ALPHA8_ETC2_EAC</code>

      <br/>

    </function>

    <function name="compressedTexSubImage2D">

      <param name="internalformat" type="GLenum"/>

      Accepted by the <code>internalformat</code> parameter:

      <code>COMPRESSED_R11_EAC</code>,

      <code>COMPRESSED_SIGNED_R11_EAC</code>,

      <code>COMPRESSED_RG11_EAC</code>,

      <code>COMPRESSED_SIGNED_RG11_EAC</code>,

      <code>COMPRESSED_RGB8_ETC2</code>,

      <code>COMPRESSED_SRGB8_ETC2</code>,

      <code>COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2</code>,

      <code>COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2</code>,

      <code>COMPRESSED_RGBA8_ETC2_EAC</code> or

      <code>COMPRESSED_SRGB8_ALPHA8_ETC2_EAC</code>

      <br/>

    </function>

  </newtok>

  <errors>

    <error enum="INVALID_VALUE">

      The error <code>INVALID_VALUE</code> is generated by <code>compressedTexImage2D</code>,

      <code>compressedTexSubImage2D</code>, <code>compressedTexImage3D</code>, and

      <code>compressedTexSubImage3D</code> if the variant taking <code>ArrayBufferView pixels</code>

      is called and the size restrictions above are not met.

    </error>

    <error enum="INVALID_OPERATION">

      The error <code>INVALID_OPERATION</code> is generated by <code>compressedTexImage2D</code>,

      <code>compressedTexSubImage2D</code>, <code>compressedTexImage3D</code>, and

      <code>compressedTexSubImage3D</code> if the variant taking <code>GLintptr offset</code> is

      called and the size restrictions above are not met.

    </error>

  </errors>

  <history>

    <revision date="2013/12/9">

      <change>Initial revision.</change>

    </revision>

    <revision date="2014/07/15">

      <change>Added NoInterfaceObject extended attribute.</change>

    </revision>

    <revision date="2014/12/12">

      <change>COMPRESSED_RGB_ETC2 should be COMPRESSED_RGB8_ETC2.</change>

      <change>Remove unnecessary language.</change>

    </revision>

    <revision date="2015/01/31">

      <change>Moved to draft.</change>

      <change>Added issue questions.</change>

      <change>Formalized the newtok and error codes.</change>

    </revision>

    <revision date="2016/09/16">

      <change>Renamed to WEBGL_compressed_texture_es3_0.</change>

    </revision>

    <revision date="2016/09/21">

      <change>Clarifications to the supported formats on suggestion from Mark Callow.</change>

    </revision>

    <revision date="2016/09/30">

      <change>Addressed issues regarding 3D entry points, description of interation with WebGL 2.0,

      and generation of INVALID_OPERATION and INVALID_VALUE errors. Added note that browsers should

      not advertise this extension if these compressed texture formats are decompressed. Renamed to

      WEBGL_compressed_texture_etc after further discussion. Promoted to community

      approved.</change>

    </revision>

  </history>

</extension>

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