MetaEgl: Add EGL extensions support

Add proc symbol loading and helper functions for calling them, dealing
with errors etc. So far no extension symbols are loaded, only the
infrastructure is there.

https://bugzilla.gnome.org/show_bug.cgi?id=773629

src/backends/meta-egl.c

@@ -109,6 +109,76 @@ set_egl_error (GError **error)
                error_str);
 }
 
+static gboolean
+extensions_string_has_extensions_valist (const char *extensions_str,
+                                         char     ***missing_extensions,
+                                         char       *first_extension,
+                                         va_list     var_args)
+{
+  char **extensions;
+  char *extension;
+  size_t num_missing_extensions = 0;
+
+  if (missing_extensions)
+    *missing_extensions = NULL;
+
+  extensions = g_strsplit (extensions_str, " ", -1);
+
+  extension = first_extension;
+  while (extension)
+    {
+      if (!g_strv_contains ((const char * const *) extensions, extension))
+        {
+          num_missing_extensions++;
+          if (missing_extensions)
+            {
+              *missing_extensions = g_realloc_n (*missing_extensions,
+                                                 num_missing_extensions + 1,
+                                                 sizeof (const char *));
+              (*missing_extensions)[num_missing_extensions - 1] = extension;
+              (*missing_extensions)[num_missing_extensions] = NULL;
+            }
+          else
+            {
+              break;
+            }
+        }
+      extension = va_arg (var_args, char *);
+    }
+
+  g_strfreev (extensions);
+
+  return num_missing_extensions == 0;
+}
+
+gboolean
+meta_egl_has_extensions (MetaEgl   *egl,
+                         EGLDisplay display,
+                         char    ***missing_extensions,
+                         char      *first_extension,
+                         ...)
+{
+  va_list var_args;
+  const char *extensions_str;
+  gboolean has_extensions;
+
+  extensions_str = (const char *) eglQueryString (display, EGL_EXTENSIONS);
+  if (!extensions_str)
+    {
+      g_warning ("Failed to query string: %s", get_egl_error_str ());
+      return FALSE;
+    }
+
+  va_start (var_args, first_extension);
+  has_extensions = extensions_string_has_extensions_valist (extensions_str,
+                                                            missing_extensions,
+                                                            first_extension,
+                                                            var_args);
+  va_end (var_args);
+
+  return has_extensions;
+}
+
 EGLDisplay
 meta_egl_get_display (MetaEgl             *egl,
                       EGLNativeDisplayType display_id,
@@ -126,6 +196,23 @@ meta_egl_get_display (MetaEgl             *egl,
   return display;
 }
 
+#define GET_EGL_PROC_ADDR(proc) \
+  egl->proc = (void *) eglGetProcAddress (#proc);
+
+#define GET_EGL_PROC_ADDR_REQUIRED(proc) \
+  GET_EGL_PROC_ADDR(proc) \
+  if (!egl->proc) \
+    { \
+      meta_fatal ("Failed to get proc address for '%s'\n", #proc); \
+    }
+
+static void
+meta_egl_constructed (GObject *object)
+{
+}
+
+#undef GET_EGL_PROC_ADDR
+
 static void
 meta_egl_init (MetaEgl *egl)
 {
@@ -134,4 +221,7 @@ meta_egl_init (MetaEgl *egl)
 static void
 meta_egl_class_init (MetaEglClass *klass)
 {
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->constructed = meta_egl_constructed;
 }

src/backends/meta-egl.h

@@ -26,11 +26,18 @@
 #define META_EGL_H
 
 #include <EGL/egl.h>
+#include <EGL/eglext.h>
 #include <glib-object.h>
 
 #define META_TYPE_EGL (meta_egl_get_type ())
 G_DECLARE_FINAL_TYPE (MetaEgl, meta_egl, META, EGL, GObject)
 
+gboolean meta_egl_has_extensions (MetaEgl   *egl,
+                                  EGLDisplay display,
+                                  char    ***missing_extensions,
+                                  char      *first_extension,
+                                  ...);
+
 EGLDisplay meta_egl_get_display (MetaEgl             *egl,
                                  EGLNativeDisplayType display_id,
                                  GError             **error);