Move all of the GL function pointers directly to CoglContext

Instead of storing all of the feature function pointers in the driver
specific data of the CoglContext they are now all stored directly in
CoglContext. There is a single header containing the description of
the functions which gets included by cogl-context.h. There is a single
function in cogl-feature-private.c to check for all of these
functions.

The name of the function pointer variables have been changed from
ctx->drv.pf_glWhatever to just ctx->glWhatever.

The feature flags that get set when an extension is available are now
separated from the table of extensions. This is necessary because
different extensions can mean different things on GLES and GL. For
example, having access to glMapBuffer implies read and write support
on GL but only write support on GLES. The flags are instead set in the
driver specific init function by checking whether the function
pointers were successfully resolved.

_cogl_feature_check has been changed to assume the feature is
supported if any of the listed extensions are available instead of
requiring all of them. This makes it more convenient to specify
alternate names for the extension. Nothing else had previously listed
more than one name for an extension so this shouldn't cause any
problems.

cogl/cogl-feature-private.c

@@ -36,8 +36,9 @@ gboolean
 _cogl_feature_check (const CoglWinsysVtable *winsys,
                      const char *driver_prefix,
                      const CoglFeatureData *data,
-                     unsigned int gl_major,
-                     unsigned int gl_minor,
+                     int gl_major,
+                     int gl_minor,
+                     CoglExtGlesAvailability gles_version,
                      const char *extensions_string,
                      void *function_table)
 
@@ -48,7 +49,8 @@ _cogl_feature_check (const CoglWinsysVtable *winsys,
   /* First check whether the functions should be directly provided by
      GL */
   if (COGL_CHECK_GL_VERSION (gl_major, gl_minor,
-                             data->min_gl_major, data->min_gl_minor))
+                             data->min_gl_major, data->min_gl_minor) ||
+      (gles_version & data->gles_availability))
     suffix = "";
   else
     {
@@ -86,16 +88,16 @@ _cogl_feature_check (const CoglWinsysVtable *winsys,
                                    namespace, namespace_len);
               g_string_append_c (full_extension_name, '_');
               g_string_append (full_extension_name, extension);
-              if (!_cogl_check_extension (full_extension_name->str,
-                                          extensions_string))
+              if (_cogl_check_extension (full_extension_name->str,
+                                         extensions_string))
                 break;
             }
 
           g_string_free (full_extension_name, TRUE);
 
-          /* If we found all of the extensions with this namespace
-             then use it as the suffix */
-          if (*extension == '\0')
+          /* If we found an extension with this namespace then use it
+             as the suffix */
+          if (*extension)
             {
               suffix = namespace_suffix;
               break;
@@ -139,3 +141,54 @@ error:
 
   return FALSE;
 }
+
+/* Define a set of arrays containing the functions required from GL
+   for each feature */
+#define COGL_EXT_BEGIN(name,                                            \
+                       min_gl_major, min_gl_minor,                      \
+                       gles_availability,                               \
+                       namespaces, extension_names)                     \
+  static const CoglFeatureFunction cogl_ext_ ## name ## _funcs[] = {
+#define COGL_EXT_FUNCTION(ret, name, args)                          \
+  { G_STRINGIFY (name), G_STRUCT_OFFSET (CoglContext, name) },
+#define COGL_EXT_END()                      \
+  { NULL, 0 },                                  \
+  };
+#include "cogl-ext-functions.h"
+
+/* Define an array of features */
+#undef COGL_EXT_BEGIN
+#define COGL_EXT_BEGIN(name,                                            \
+                       min_gl_major, min_gl_minor,                      \
+                       gles_availability,                               \
+                       namespaces, extension_names)                     \
+  { min_gl_major, min_gl_minor, gles_availability, namespaces,          \
+      extension_names, 0, 0, 0,                                         \
+    cogl_ext_ ## name ## _funcs },
+#undef COGL_EXT_FUNCTION
+#define COGL_EXT_FUNCTION(ret, name, args)
+#undef COGL_EXT_END
+#define COGL_EXT_END()
+
+static const CoglFeatureData
+cogl_feature_ext_functions_data[] =
+  {
+#include "cogl-ext-functions.h"
+  };
+
+void
+_cogl_feature_check_ext_functions (CoglContext *context,
+                                   int gl_major,
+                                   int gl_minor,
+                                   const char *gl_extensions,
+                                   CoglExtGlesAvailability gles_version)
+{
+  int i;
+
+  for (i = 0; i < G_N_ELEMENTS (cogl_feature_ext_functions_data); i++)
+    _cogl_feature_check (_cogl_context_get_winsys (context),
+                         "GL", cogl_feature_ext_functions_data + i,
+                         gl_major, gl_minor, gles_version,
+                         gl_extensions,
+                         context);
+}