docs/WL_bind_wayland_display.spec

   1 Name
   2
   3     WL_bind_wayland_display
   4
   5 Name Strings
   6
   7     EGL_WL_bind_wayland_display
   8
   9 Contact
  10
  11     Kristian Høgsberg <krh@bitplanet.net>
  12     Benjamin Franzke <benjaminfranzke@googlemail.com>
  13
  14 Status
  15
  16     Proposal
  17
  18 Version
  19
  20     Version 1, March 1, 2011
  21
  22 Number
  23
  24     EGL Extension #not assigned
  25
  26 Dependencies
  27
  28     Requires EGL 1.4 or later.  This extension is written against the
  29     wording of the EGL 1.4 specification.
  30
  31     EGL_KHR_base_image is required.
  32
  33 Overview
  34
  35     This extension provides entry points for binding and unbinding the
  36     wl_display of a Wayland compositor to an EGLDisplay.  Binding a
  37     wl_display means that the EGL implementation should provide one or
  38     more interfaces in the Wayland protocol to allow clients to create
  39     wl_buffer objects.  On the server side, this extension also
  40     provides a new target for eglCreateImageKHR, to create an EGLImage
  41     from a wl_buffer
  42
  43     Adding an implementation specific wayland interface, allows the
  44     EGL implementation to define specific wayland requests and events,
  45     needed for buffer sharing in an EGL wayland platform.
  46
  47 IP Status
  48
  49     Open-source; freely implementable.
  50
  51 New Procedures and Functions
  52
  53     EGLBoolean eglBindWaylandDisplayWL(EGLDisplay dpy,
  54                                        struct wl_display *display);
  55
  56     EGLBoolean eglUnbindWaylandDisplayWL(EGLDisplay dpy,
  57                                          struct wl_display *display);
  58
  59     EGLBoolean eglQueryWaylandBufferWL(EGLDisplay dpy,
  60                                        struct wl_buffer *buffer,
  61                                        EGLint attribute, EGLint *value);
  62
  63 New Tokens
  64
  65     Accepted as <target> in eglCreateImageKHR
  66
  67         EGL_WAYLAND_BUFFER_WL                   0x31D5
  68
  69     Accepted in the <attrib_list> parameter of eglCreateImageKHR:
  70
  71         EGL_WAYLAND_PLANE_WL                    0x31D6
  72
  73     Possible values for EGL_TEXTURE_FORMAT:
  74
  75         EGL_TEXTURE_Y_U_V_WL                    0x31D7
  76         EGL_TEXTURE_Y_UV_WL                     0x31D8
  77         EGL_TEXTURE_Y_XUXV_WL                   0x31D9
  78
  79
  80 Additions to the EGL 1.4 Specification:
  81
  82     To bind a server side wl_display to an EGLDisplay, call
  83
  84         EGLBoolean eglBindWaylandDisplayWL(EGLDisplay dpy,
  85                                            struct wl_display *display);
  86
  87     To unbind a server side wl_display from an EGLDisplay, call
  88
  89         EGLBoolean eglUnbindWaylandDisplayWL(EGLDisplay dpy,
  90                                              struct wl_display *display);
  91
  92     eglBindWaylandDisplayWL returns EGL_FALSE when there is already a
  93     wl_display bound to EGLDisplay otherwise EGL_TRUE.
  94
  95     eglUnbindWaylandDisplayWL returns EGL_FALSE when there is no
  96     wl_display bound to the EGLDisplay currently otherwise EGL_TRUE.
  97
  98     A wl_buffer can have several planes, typically in case of planar
  99     YUV formats.  Depending on the exact YUV format in use, the
 100     compositor will have to create one or more EGLImages for the
 101     various planes.  The eglQueryWaylandBufferWL function should be
 102     used to first query the wl_buffer texture format using
 103     EGL_TEXTURE_FORMAT as the attribute.  If the wl_buffer object is
 104     not an EGL wl_buffer (wl_shm and other wayland extensions can
 105     create wl_buffer objects of different types), this query will
 106     return EGL_FALSE.  In that case the wl_buffer can not be used with
 107     EGL and the compositor should have another way to get the buffer
 108     contents.
 109
 110     If eglQueryWaylandBufferWL succeeds, the returned value will be
 111     one of EGL_TEXTURE_RGB, EGL_TEXTURE_RGBA, EGL_TEXTURE_Y_U_V_WL,
 112     EGL_TEXTURE_Y_UV_WL, EGL_TEXTURE_Y_XUXV_WL.  The value returned
 113     describes how many EGLImages must be used, which components will
 114     be sampled from each EGLImage and how they map to rgba components
 115     in the shader.  The naming conventions separates planes by _ and
 116     within each plane, the order or R, G, B, A, Y, U, and V indicates
 117     how those components map to the rgba value returned by the
 118     sampler.  X indicates that the corresponding component in the rgba
 119     value isn't used.
 120
 121     RGB and RGBA buffer types:
 122
 123         EGL_TEXTURE_RGB
 124                 One plane, samples RGB from the texture to rgb in the
 125                 shader.  Alpha channel is not valid.
 126
 127         EGL_TEXTURE_RGBA
 128                 One plane, samples RGBA from the texture to rgba in the
 129                 shader.
 130
 131     YUV buffer types:
 132
 133         EGL_TEXTURE_Y_U_V_WL
 134                 Three planes, samples Y from the first plane to r in
 135                 the shader, U from the second plane to r, and V from
 136                 the third plane to r.
 137
 138         EGL_TEXTURE_Y_UV_WL
 139                 Two planes, samples Y from the first plane to r in
 140                 the shader, U and V from the second plane to rg.
 141
 142         EGL_TEXTURE_Y_XUXV_WL
 143                 Two planes, samples Y from the first plane to r in
 144                 the shader, U and V from the second plane to g and a.
 145
 146     After querying the wl_buffer layout, create EGLImages for the
 147     planes by calling eglCreateImageKHR with wl_buffer as
 148     EGLClientBuffer, EGL_WAYLAND_BUFFER_WL as the target, NULL
 149     context.  If no attributes are given, an EGLImage will be created
 150     for the first plane.  For multi-planar buffers, specify the plane
 151     to create the EGLImage for by using the EGL_WAYLAND_PLANE_WL
 152     attribute.  The value of the attribute is the index of the plane,
 153     as defined by the buffer format.  Writing to an EGLImage created
 154     from a wl_buffer in any way (such as glTexImage2D, binding the
 155     EGLImage as a renderbuffer etc) will result in undefined behavior.
 156
 157 Issues
 158
 159 Revision History
 160
 161     Version 1, March 1, 2011
 162         Initial draft (Benjamin Franzke)
 163     Version 2, July 5, 2012
 164         Add EGL_WAYLAND_PLANE_WL attribute to allow creating an EGLImage
 165         for different planes of planar buffer. (Kristian Høgsberg)
 166     Version 3, July 10, 2012
 167         Add eglQueryWaylandBufferWL and the various buffer
 168         formats. (Kristian Høgsberg)
 169     Version 4, July 19, 2012
 170         Use EGL_TEXTURE_FORMAT, EGL_TEXTURE_RGB, and EGL_TEXTURE_RGBA,
 171         and just define the new YUV texture formats. (Kristian Høgsberg)