Dynamically load the GL or GLES library

The GL or GLES library is now dynamically loaded by the CoglRenderer
so that it can choose between GL, GLES1 and GLES2 at runtime. The
library is loaded by the renderer because it needs to be done before
calling eglInitialize. There is a new environment variable called
COGL_DRIVER to choose between gl, gles1 or gles2.

The #ifdefs for HAVE_COGL_GL, HAVE_COGL_GLES and HAVE_COGL_GLES2 have
been changed so that they don't assume the ifdefs are mutually
exclusive. They haven't been removed entirely so that it's possible to
compile the GLES backends without the the enums from the GL headers.

When using GLX the winsys additionally dynamically loads libGL because
that also contains the GLX API. It can't be linked in directly because
that would probably conflict with the GLES API if the EGL is
selected. When compiling with EGL support the library links directly
to libEGL because it doesn't contain any GL API so it shouldn't have
any conflicts.

When building for WGL or OSX Cogl still directly links against the GL
API so there is a #define in config.h so that Cogl won't try to dlopen
the library.

Cogl-pango previously had a #ifdef to detect when the GL backend is
used so that it can sneakily pass GL_QUADS to
cogl_vertex_buffer_draw. This is now changed so that it queries the
CoglContext for the backend. However to get this to work Cogl now
needs to export the _cogl_context_get_default symbol and cogl-pango
needs some extra -I flags to so that it can include
cogl-context-private.h

2 files changed, 25 insertions, 22 deletions

diff --git a/cogl-pango/Makefile.am b/cogl-pango/Makefile.am
index b57e1474..afd96d6b 100644
--- a/cogl-pango/Makefile.am
+++ b/cogl-pango/Makefile.am
@@ -40,6 +40,8 @@ INCLUDES = \
 	-DG_DISABLE_SINGLE_INCLUDES	\
 	-DCLUTTER_COMPILATION		\
 	-DG_LOG_DOMAIN=\"CoglPango\"	\
+	-I$(top_srcdir)/cogl		\
+	-I$(top_srcdir)/cogl/winsys	\
 	-I$(top_srcdir)			\
 	-I$(top_builddir)
 
diff --git a/cogl-pango/cogl-pango-display-list.c b/cogl-pango/cogl-pango-display-list.c
index a79cf0f1..84400066 100644
--- a/cogl-pango/cogl-pango-display-list.c
+++ b/cogl-pango/cogl-pango-display-list.c
@@ -30,6 +30,7 @@
 #include <string.h>
 
 #include "cogl-pango-display-list.h"
+#include "cogl/cogl-context-private.h"
 
 typedef enum
 {
@@ -265,6 +266,8 @@ emit_rectangles_through_journal (CoglPangoDisplayListNode *node)
 static void
 emit_vertex_buffer_geometry (CoglPangoDisplayListNode *node)
 {
+  _COGL_GET_CONTEXT (ctx, NO_RETVAL);
+
   /* It's expensive to go through the Cogl journal for large runs
    * of text in part because the journal transforms the quads in software
    * to avoid changing the modelview matrix. So for larger runs of text
@@ -293,29 +296,27 @@ emit_vertex_buffer_geometry (CoglPangoDisplayListNode *node)
       node->d.texture.vertex_buffer = vb;
     }
 
-
 #ifdef CLUTTER_COGL_HAS_GL
-
-  cogl_vertex_buffer_draw (node->d.texture.vertex_buffer,
-                           GL_QUADS,
-                           0, node->d.texture.verts->len);
-
-#else /* CLUTTER_COGL_HAS_GL */
-  {
-    /* GLES doesn't support GL_QUADS so instead we use a VBO with
-       indexed vertices to generate GL_TRIANGLES from the quads */
-
-    int n_indices = node->d.texture.verts->len / 4 * 6;
-    CoglHandle indices_vbo
-      = cogl_vertex_buffer_indices_get_for_quads (n_indices);
-
-    cogl_vertex_buffer_draw_elements (node->d.texture.vertex_buffer,
-                                      COGL_VERTICES_MODE_TRIANGLES,
-                                      indices_vbo,
-                                      0, node->d.texture.verts->len - 1,
-                                      0, n_indices);
-  }
-#endif /* CLUTTER_COGL_HAS_GL */
+  if (ctx->driver == COGL_DRIVER_GL)
+    cogl_vertex_buffer_draw (node->d.texture.vertex_buffer,
+                             GL_QUADS,
+                             0, node->d.texture.verts->len);
+  else
+#endif
+    {
+      /* GLES doesn't support GL_QUADS so instead we use a VBO with
+         indexed vertices to generate GL_TRIANGLES from the quads */
+
+      int n_indices = node->d.texture.verts->len / 4 * 6;
+      CoglHandle indices_vbo
+        = cogl_vertex_buffer_indices_get_for_quads (n_indices);
+
+      cogl_vertex_buffer_draw_elements (node->d.texture.vertex_buffer,
+                                        COGL_VERTICES_MODE_TRIANGLES,
+                                        indices_vbo,
+                                        0, node->d.texture.verts->len - 1,
+                                        0, n_indices);
+    }
 }
 
 static void