gl-renderer: Use EGL_KHR_no_config_context

This patch makes use of recently implemented
EGL_KHR_no_config_context extension in Mesa,
which superseeds EGL_MESA_configless_context.

See also (and the follow-up patch):

https://lists.freedesktop.org/archives/mesa-dev/2016-September/128510.html

v2:

 - Extend existing infrastructure for EGL_MESA_configless_context
   per suggestion from Emmanuel Gil Peyrot.

Signed-off-by: Armin Krezović <krezovic.armin@gmail.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

libweston/gl-renderer.c

@@ -2660,8 +2660,8 @@ gl_renderer_create_window_surface(struct gl_renderer *gr,
 	if (egl_config != gr->egl_config &&
 	    !gr->has_configless_context) {
 		weston_log("attempted to use a different EGL config for an "
-			   "output but EGL_MESA_configless_context is not "
-			   "supported\n");
+			   "output but EGL_KHR_no_config_context or "
+			   "EGL_MESA_configless_context is not supported\n");
 		return EGL_NO_SURFACE;
 	}
 
@@ -2853,7 +2853,8 @@ gl_renderer_setup_egl_extensions(struct weston_compositor *ec)
 		weston_log("warning: EGL_EXT_swap_buffers_with_damage not "
 			   "supported. Performance could be affected.\n");
 
-	if (weston_check_egl_extension(extensions, "EGL_MESA_configless_context"))
+	if (weston_check_egl_extension(extensions, "EGL_KHR_no_config_context") ||
+	    weston_check_egl_extension(extensions, "EGL_MESA_configless_context"))
 		gr->has_configless_context = 1;
 
 	if (weston_check_egl_extension(extensions, "EGL_KHR_surfaceless_context"))
@@ -3234,7 +3235,7 @@ gl_renderer_setup(struct weston_compositor *ec, EGLSurface egl_surface)
 	context_config = gr->egl_config;
 
 	if (gr->has_configless_context)
-		context_config = EGL_NO_CONFIG_MESA;
+		context_config = EGL_NO_CONFIG_KHR;
 
 	gr->egl_context = eglCreateContext(gr->egl_display, context_config,
 					   EGL_NO_CONTEXT, context_attribs);

libweston/weston-egl-ext.h

@@ -135,6 +135,10 @@ typedef EGLBoolean (EGLAPIENTRYP PFNEGLSWAPBUFFERSWITHDAMAGEEXTPROC) (EGLDisplay
 #define EGL_NO_CONFIG_MESA                      ((EGLConfig)0)
 #endif
 
+#ifndef EGL_NO_CONFIG_KHR
+#define EGL_NO_CONFIG_KHR ((EGLConfig)0)
+#endif
+
 #ifndef EGL_EXT_platform_base
 #define EGL_EXT_platform_base 1
 typedef EGLDisplay (EGLAPIENTRYP PFNEGLGETPLATFORMDISPLAYEXTPROC) (EGLenum platform, void *native_display, const EGLint *attrib_list);