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      1 Name
      2 
      3     CHROMIUM_texture_mailbox
      4 
      5 Name Strings
      6 
      7     GL_CHROMIUM_texture_mailbox
      8 
      9 Version
     10 
     11     Last Modifed Date: April 25, 2012
     12 
     13 Dependencies
     14 
     15     OpenGL ES 2.0 is required.
     16 
     17 Overview
     18 
     19     This extension defines a way of sharing texture image data between texture
     20     objects in different contexts where the contexts would not normally share
     21     texture resources. Three new functions are exported. glGenMailboxCHROMIUM
     22     generates a name that can be used to identify texture image data outside
     23     the scope of a context group. glProduceMailboxCHROMIUM associates a texture
     24     object with a global mailbox name. glConsumeMailboxCHROMIUM associates the
     25     texture object referenced by a mailbox name to a texture name.
     26 
     27 New Procedures and Functions
     28 
     29     void glGenMailboxCHROMIUM (GLbyte *mailbox)
     30 
     31     Generates a unique name identifying a mailbox. The name is generated using
     32     a cryptographic random number generator and is intended to be difficult to
     33     guess. The scope of the name is implementation specific, for example it
     34     might not span multiple displays.
     35 
     36     <mailbox> returns a GL_MAILBOX_SIZE_CHROMIUM byte sized name
     37 
     38 
     39     void glProduceTextureCHROMIUM (GLenum target, const GLbyte *mailbox)
     40 
     41     Associates the currently bound texture object with the mailbox name. A
     42     given texture object can be associated with several mailbox names. If a
     43     mailbox name was previously associated with a texture object, that
     44     previous association is broken. The currently bound texture object is not
     45     modified by the operation.
     46 
     47     If glProduceTextureCHROMIUM generates an error, the mailbox name keeps its
     48     current association, if any.
     49 
     50     The mailbox does not keep a reference to the texture object. When the
     51     texture object is destroyed (deleted from all context groups, and unbound
     52     from all texture units and framebuffer attachments), the mailbox is
     53     disassociated from the texture object.
     54 
     55     <target> uses the same parameters as TexImage2D.
     56 
     57     <mailbox> identifies a GL_MAILBOX_SIZE_CHROMIUM byte sized name returned by
     58     glGenMailboxCHROMIUM.
     59 
     60     INVALID_OPERATION is generated if <target> is not a valid target.
     61 
     62     INVALID_OPERATION is generated if <mailbox> is invalid.
     63 
     64 
     65     void glConsumeTextureCHROMIUM (GLenum target, const GLbyte *mailbox)
     66 
     67     <target> uses the same parameters as TexImage2D.
     68 
     69     <mailbox> identifies a GL_MAILBOX_SIZE_CHROMIUM byte sized name returned by
     70     glGenMailboxCHROMIUM.
     71     
     72     Deletes the currently bound texture object, and redefines its texture name
     73     to point to the texture object associated with the mailbox name. All the
     74     contexts that have consumed the texture object, as well as produced it share
     75     the texture object, as if the contexts were part of the share group. The
     76     texture object is deleted once all contexts have deleted the texture name
     77     associated with the texture object, and detached it from all framebuffer
     78     objects as well as texture unit bindings. See Appendix C of the OpenGL ES
     79     2.0 specification for details relative to visibility in one context of
     80     changes to the shared texture object in another context.
     81 
     82     If glConsumeTextureCHROMIUM generates an error, the currently bound texture
     83     object is preserved.
     84 
     85     INVALID_OPERATION is generated if <target> is not a valid target.
     86 
     87     INVALID_OPERATION is generated if <mailbox> is invalid.
     88 
     89     INVALID_OPERATION is generated if <mailbox> is not associated with a texture
     90     object.
     91 
     92     INVALID_OPERATION is generated if the texture object associated with
     93     <mailbox> has a different target than <target>.
     94 
     95     INVALID_OPERATION is generated if the currently bound texture was previously
     96     deleted (for example in another context), hence doesn't have a name.
     97 
     98 New Tokens
     99 
    100     The size of a mailbox name in bytes.
    101 
    102         GL_MAILBOX_SIZE_CHROMIUM                             64
    103 
    104 Errors
    105 
    106     None.
    107 
    108 New Tokens
    109 
    110     None.
    111 
    112 New State
    113 
    114     None.
    115 
    116 Revision History
    117 
    118     4/25/2011    Documented the extension
    119     5/23/2013    Major revision in Produce/Consume semantics, introducing
    120                  sharing.
    121