On Thu, 2019-04-04 at 16:25 +0100, Emil Velikov wrote:
> I'm not a huge fan of this. Yet again the other platform (x11) that uses
> these has a number of issues, see below for details. Once those are resolved
> we could try and make this more uniform.
>
> a) spec does not mention if a new (or the existing) EGLDislay should be
> given for same native_dpy/screen_no combo.
An EGLDisplay maps to an X11 screen. EGL_KHR_platform_x11 says:
> On the X11 platform, an EGLDisplay refers to a specific X11 screen rather
> than an X11 display connection.
And EGL 1.5 says (with similar text in EGL_EXT_platform_base):
> Multiple calls made to eglGetPlatformDisplay with the same parameters will
> return the same EGLDisplay handle.
EGL_KHR_platform_x11 is a little confusing on this point in one of the
issues, because it says a new display connection is created for
EGL_DEFAULT_DISPLAY; presumably that's only for the first EGLDisplay
you create though.
> b) the implementation has number of issues:
> - screen 0 is hardcoded when using DEFAULT_DISPLAY
False, but:
> - screen is _ignored_ when using !DEFAULT_DISPLAY
true, but easily fixed. We definitely store the screen number in
disp->Options.Platform in _eglParseX11DisplayAttribList, and then:
> static EGLBoolean
>
> dri2_get_xcb_connection(_EGLDriver *drv, _EGLDisplay *disp,
>
> struct dri2_egl_display *dri2_dpy)
>
> {
>
> xcb_screen_iterator_t s;
>
> int screen = (uintptr_t)disp->Options.Platform;
>
> const char *msg;
>
>
>
> disp->DriverData = (void *) dri2_dpy;
>
> if (disp->PlatformDisplay == NULL) {
>
> dri2_dpy->conn = xcb_connect(NULL, &screen);
>
> dri2_dpy->own_device = true;
If no display was given, we connect however xcb would, and save what it
decided was the default screen number.
> } else {
>
> Display *dpy = disp->PlatformDisplay;
>
>
>
> dri2_dpy->conn = XGetXCBConnection(dpy);
>
> screen = DefaultScreen(dpy);
>
> }
If not, we use what the display already had set; this is where we
ignore the user's screen number and instead use the display's default.
I think the fix is to delete that DefaultScreen line above, and in
_eglFindDisplay call the appropriate platform's vtable to check for
identical option lists (this is your _eglSameDeviceDisplay in the next
patch, just abstracted out a bit).
- ajax
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