[PATCH] compositor: Set EGL_PLATFORM env variable for each backend.

[Kristian Høgsberg]

On Tue, May 10, 2011 at 4:13 PM, Casey Dahlin <cdahlin at redhat.com> wrote:
> On Tue, May 10, 2011 at 08:00:19PM +0000, Egbert Eich wrote:
>> I may have missed something, but - since the Wayland compositor
>> already picks a platform backend, opens a connection and initializes the
>> backend specific display data structure it doesn't make sense
>> to let egl pick a platform. If it picks a different one the
>> display specific data structure will most likely not match.
>> Thus determine the platform in the Wayland rendering backend by setting
>> the EGL_PLATFORM env variable.
>> For the client any other platform than 'wayland' doesn't seem to make
>> sense.
>> I'm not sure if I've got the the platform ofr openfwd right.
>>
>> Signed-off-by: Egbert Eich <eich at freedesktop.org>
>
> This is one of many ways to hack around the somewhat deficient platform
> selection in EGL (which in turn is a product of attempting to implement
> the spec as best as they can).
>
> Some sort of architectural fix for mesa would probably be preferred, but
> nobody has yet found one that people will agree on.

Indeed.  I'll commit this patch for now, since I've had enough of
failing to set EGL_PLATFORM and then trying to figure out why it
breaks.  The best solution I know of at this point is a "magic" way to
look at the native display argument and detect what kind it is.  So
for example, stat it to see if it's a char device, in which case we
decide it's the drm platform.  If not, assume it's a pointer a struct
and see if the first field looks like a valid pointer (not NULL and a
multiple of 4), in which case we assume it's a X display pointer
(Xlib.h, line 506).  For the wl_display struct we can make the first
field a pointer to a wayland symbol which will let us distinguish it
from an X display pointer.

It's ugly and magic, but given the API we're stuck with, it's a fine workaround.

Kristian

> --CJD
>
>> ---
>>  clients/window.c                |    1 +
>>  compositor/compositor-drm.c     |    1 +
>>  compositor/compositor-openwfd.c |    1 +
>>  compositor/compositor-wayland.c |    1 +
>>  compositor/compositor-x11.c     |    1 +
>>  5 files changed, 5 insertions(+), 0 deletions(-)
>>
>> diff --git a/clients/window.c b/clients/window.c
>> index 9d0b753..8c3f8d2 100644
>> --- a/clients/window.c
>> +++ b/clients/window.c
>> @@ -1757,6 +1757,7 @@ init_egl(struct display *d)
>>               EGL_NONE
>>       };
>>
>> +     setenv("EGL_PLATFORM", "wayland", 1);
>>       d->dpy = eglGetDisplay(d->display);
>>       if (!eglInitialize(d->dpy, &major, &minor)) {
>>               fprintf(stderr, "failed to initialize display\n");
>> diff --git a/compositor/compositor-drm.c b/compositor/compositor-drm.c
>> index 4897b38..9fc5b49 100644
>> --- a/compositor/compositor-drm.c
>> +++ b/compositor/compositor-drm.c
>> @@ -269,6 +269,7 @@ init_egl(struct drm_compositor *ec, struct udev_device *device)
>>               return -1;
>>       }
>>
>> +     setenv("EGL_PLATFORM", "drm", 1);
>>       ec->drm.fd = fd;
>>       ec->base.display = eglGetDisplay(FD_TO_EGL_NATIVE_DPY(ec->drm.fd));
>>       if (ec->base.display == NULL) {
>> diff --git a/compositor/compositor-openwfd.c b/compositor/compositor-openwfd.c
>> index 0ddde52..ccd3dce 100644
>> --- a/compositor/compositor-openwfd.c
>> +++ b/compositor/compositor-openwfd.c
>> @@ -118,6 +118,7 @@ init_egl(struct wfd_compositor *ec)
>>               return -1;
>>
>>       ec->wfd_fd = fd;
>> +     setenv("EGL_PLATFORM", "drm", 1);
>>       ec->base.display = eglGetDisplay(FD_TO_EGL_NATIVE_DPY(ec->wfd_fd));
>>       if (ec->base.display == NULL) {
>>               fprintf(stderr, "failed to create display\n");
>> diff --git a/compositor/compositor-wayland.c b/compositor/compositor-wayland.c
>> index 1a53e8d..6cd02ed 100644
>> --- a/compositor/compositor-wayland.c
>> +++ b/compositor/compositor-wayland.c
>> @@ -111,6 +111,7 @@ wayland_compositor_init_egl(struct wayland_compositor *c)
>>               EGL_NONE
>>       };
>>
>> +     setenv("EGL_PLATFORM", "wayland", 1);
>>       c->base.display = eglGetDisplay(c->parent.display);
>>       if (c->base.display == NULL) {
>>               fprintf(stderr, "failed to create display\n");
>> diff --git a/compositor/compositor-x11.c b/compositor/compositor-x11.c
>> index ac31881..3517fad 100644
>> --- a/compositor/compositor-x11.c
>> +++ b/compositor/compositor-x11.c
>> @@ -113,6 +113,7 @@ x11_compositor_init_egl(struct x11_compositor *c)
>>               EGL_NONE
>>       };
>>
>> +     setenv("EGL_PLATFORM", "x11", 1);
>>       c->base.display = eglGetDisplay(c->dpy);
>>       if (c->base.display == NULL) {
>>               fprintf(stderr, "failed to create display\n");
>> --
>> 1.7.3.4
>>
>>
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>> wayland-devel at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/wayland-devel
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