cogl: Make it easier to add checks for GL extensions

Previously if you need to depend on a new GL feature you had to:

- Add typedefs for all of the functions in cogl-defines.h.in

- Add function pointers for each of the functions in
  cogl-context-driver.h

- Add an initializer for the function pointers in
  cogl-context-driver.c

- Add a check for the extension and all of the functions in
  cogl_features_init. If the extension is available under multiple
  names then you have to duplicate the checks.

This is quite tedious and error prone. This patch moves all of the
features and their functions into a list of macro invocations in
cogl-feature-functions.h. The macros can be redefined to implement all
of the above tasks from the same header.

The features are described in a struct with a pointer to a table of
functions. A new function takes the feature description from this
struct and checks for its availability. The feature can take a list of
extension names with a list of alternate namespaces (such as "EXT" or
"ARB"). It can also detect the feature from a particular version of
GL.

The typedefs are now gone and instead the function pointer in the Cogl
context just directly contains the type.

Some of the functions in the context were previously declared with the
'ARB' extension. This has been removed so that now all the functions
have no suffix. This makes more sense when the extension could
potentially be merged into GL core as well.

1 files changed, 71 insertions, 0 deletions

diff --git a/cogl/cogl-feature-private.h b/cogl/cogl-feature-private.h
new file mode 100644
index 00000000..0782669b
--- /dev/null
+++ b/cogl/cogl-feature-private.h
@@ -0,0 +1,71 @@
+/*
+ * Cogl
+ *
+ * An object oriented GL/GLES Abstraction/Utility Layer
+ *
+ * Copyright (C) 2009 Intel Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef __COGL_FEATURE_PRIVATE_H
+#define __COGL_FEATURE_PRIVATE_H
+
+#include <glib.h>
+
+#define COGL_CHECK_GL_VERSION(driver_major, driver_minor, \
+                              target_major, target_minor) \
+  ((driver_major) > (target_major) || \
+   ((driver_major) == (target_major) && (driver_minor) >= (target_minor)))
+
+typedef struct _CoglFeatureFunction CoglFeatureFunction;
+
+struct _CoglFeatureFunction
+{
+  /* The name of the function without the "EXT" or "ARB" suffix */
+  const gchar *name;
+  /* The offset in the context of where to store the function pointer */
+  guint pointer_offset;
+};
+
+typedef struct _CoglFeatureData CoglFeatureData;
+
+struct _CoglFeatureData
+{
+  /* A minimum GL version which the functions should be defined in
+     without needing an extension. Set to 255,255 if it's only
+     provided in an extension */
+  guchar min_gl_major, min_gl_minor;
+  /* \0 separated list of namespaces to try. Eg "EXT\0ARB\0" */
+  const gchar *namespaces;
+  /* \0 separated list of required extension names without the GL_EXT
+     or GL_ARB prefix. All of the extensions must be available for the
+     feature to be considered available. If the suffix for an
+     extension is different from the namespace, you can specify it
+     with a ':' after the namespace */
+  const gchar *extension_names;
+  /* A set of feature flags to enable if the extension is available */
+  CoglFeatureFlags feature_flags;
+  /* A list of functions required for this feature. Terminated with a
+     NULL name */
+  const CoglFeatureFunction *functions;
+};
+
+gboolean _cogl_feature_check (const CoglFeatureData *data,
+                              guint gl_major, guint gl_minor,
+                              const gchar *extensions_string);
+
+#endif /* __COGL_FEATURE_PRIVATE_H */