Name
WL_bind_wayland_display
Name Strings
EGL_WL_bind_wayland_display
Contact
Kristian Høgsberg <krh@bitplanet.net>
Benjamin Franzke <benjaminfranzke@googlemail.com>
Status
Proposal
Version
Version 1, March 1, 2011
Number
EGL Extension #not assigned
Dependencies
Requires EGL 1.4 or later. This extension is written against the
wording of the EGL 1.4 specification.
EGL_KHR_base_image is required.
Overview
This extension provides entry points for binding and unbinding the
wl_display of a Wayland compositor to an EGLDisplay. Binding a
wl_display means that the EGL implementation should provide one or
more interfaces in the Wayland protocol to allow clients to create
wl_buffer objects. On the server side, this extension also
provides a new target for eglCreateImageKHR, to create an EGLImage
from a wl_buffer
Adding an implementation specific wayland interface, allows the
EGL implementation to define specific wayland requests and events,
needed for buffer sharing in an EGL wayland platform.
IP Status
Open-source; freely implementable.
New Procedures and Functions
EGLBoolean eglBindWaylandDisplayWL(EGLDisplay dpy,
struct wl_display *display);
EGLBoolean eglUnbindWaylandDisplayWL(EGLDisplay dpy,
struct wl_display *display);
EGLBoolean eglQueryWaylandBufferWL(EGLDisplay dpy,
struct wl_buffer *buffer,
EGLint attribute, EGLint *value);
New Tokens
Accepted as <target> in eglCreateImageKHR
EGL_WAYLAND_BUFFER_WL 0x31D5
Accepted in the <attrib_list> parameter of eglCreateImageKHR:
EGL_WAYLAND_PLANE_WL 0x31D6
Possible values for EGL_TEXTURE_FORMAT:
EGL_TEXTURE_Y_U_V_WL 0x31D7
EGL_TEXTURE_Y_UV_WL 0x31D8
EGL_TEXTURE_Y_XUXV_WL 0x31D9
Additions to the EGL 1.4 Specification:
To bind a server side wl_display to an EGLDisplay, call
EGLBoolean eglBindWaylandDisplayWL(EGLDisplay dpy,
struct wl_display *display);
To unbind a server side wl_display from an EGLDisplay, call
EGLBoolean eglUnbindWaylandDisplayWL(EGLDisplay dpy,
struct wl_display *display);
eglBindWaylandDisplayWL returns EGL_FALSE when there is already a
wl_display bound to EGLDisplay otherwise EGL_TRUE.
eglUnbindWaylandDisplayWL returns EGL_FALSE when there is no
wl_display bound to the EGLDisplay currently otherwise EGL_TRUE.
A wl_buffer can have several planes, typically in case of planar
YUV formats. Depending on the exact YUV format in use, the
compositor will have to create one or more EGLImages for the
various planes. The eglQueryWaylandBufferWL function should be
used to first query the wl_buffer texture format using
EGL_TEXTURE_FORMAT as the attribute. If the wl_buffer object is
not an EGL wl_buffer (wl_shm and other wayland extensions can
create wl_buffer objects of different types), this query will
return EGL_FALSE. In that case the wl_buffer can not be used with
EGL and the compositor should have another way to get the buffer
contents.
If eglQueryWaylandBufferWL succeeds, the returned value will be
one of EGL_TEXTURE_RGB, EGL_TEXTURE_RGBA, EGL_TEXTURE_Y_U_V_WL,
EGL_TEXTURE_Y_UV_WL, EGL_TEXTURE_Y_XUXV_WL. The value returned
describes how many EGLImages must be used, which components will
be sampled from each EGLImage and how they map to rgba components
in the shader. The naming conventions separates planes by _ and
within each plane, the order or R, G, B, A, Y, U, and V indicates
how those components map to the rgba value returned by the
sampler. X indicates that the corresponding component in the rgba
value isn't used.
RGB and RGBA buffer types:
EGL_TEXTURE_RGB
One plane, samples RGB from the texture to rgb in the
shader. Alpha channel is not valid.
EGL_TEXTURE_RGBA
One plane, samples RGBA from the texture to rgba in the
shader.
YUV buffer types:
EGL_TEXTURE_Y_U_V_WL
Three planes, samples Y from the first plane to r in
the shader, U from the second plane to r, and V from
the third plane to r.
EGL_TEXTURE_Y_UV_WL
Two planes, samples Y from the first plane to r in
the shader, U and V from the second plane to rg.
EGL_TEXTURE_Y_XUXV_WL
Two planes, samples Y from the first plane to r in
the shader, U and V from the second plane to g and a.
After querying the wl_buffer layout, create EGLImages for the
planes by calling eglCreateImageKHR with wl_buffer as
EGLClientBuffer, EGL_WAYLAND_BUFFER_WL as the target, NULL
context. If no attributes are given, an EGLImage will be created
for the first plane. For multi-planar buffers, specify the plane
to create the EGLImage for by using the EGL_WAYLAND_PLANE_WL
attribute. The value of the attribute is the index of the plane,
as defined by the buffer format. Writing to an EGLImage created
from a wl_buffer in any way (such as glTexImage2D, binding the
EGLImage as a renderbuffer etc) will result in undefined behavior.
Further, eglQueryWaylandBufferWL accepts attributes EGL_WIDTH and
EGL_HEIGHT to query the width and height of the wl_buffer.
Issues
Revision History
Version 1, March 1, 2011
Initial draft (Benjamin Franzke)
Version 2, July 5, 2012
Add EGL_WAYLAND_PLANE_WL attribute to allow creating an EGLImage
for different planes of planar buffer. (Kristian Høgsberg)
Version 3, July 10, 2012
Add eglQueryWaylandBufferWL and the various buffer
formats. (Kristian Høgsberg)
Version 4, July 19, 2012
Use EGL_TEXTURE_FORMAT, EGL_TEXTURE_RGB, and EGL_TEXTURE_RGBA,
and just define the new YUV texture formats. Add support for
EGL_WIDTH and EGL_HEIGHT in the query attributes (Kristian Høgsberg)