[grits] Support OpenGL extensions under Win32

[Andy Spencer <andys src gnome org>]

commit c605da71628f672c2ff94018e92eb245685d51a1
Author: Andy Spencer <andy753421 gmail com>
Date:   Thu Feb 16 21:34:21 2012 +0000

    Support OpenGL extensions under Win32

 src/gtkgl.c                |   38 +++++++++++++++++++++++++++++++++++++-
 src/objects/grits-marker.c |    4 ++++
 src/objects/grits-tile.c   |    5 +++++
 3 files changed, 46 insertions(+), 1 deletions(-)
---
diff --git a/src/gtkgl.c b/src/gtkgl.c
index bb87494..b10c52d 100644
--- a/src/gtkgl.c
+++ b/src/gtkgl.c
@@ -119,6 +119,42 @@ void gtk_gl_disable(GtkWidget *widget)
 #elif defined(SYS_WIN)
 #include <windows.h>
 #include <gdk/gdkwin32.h>
+#include <GL/gl.h>
+
+/* Windows doens't define OpenGL extensions */
+static void APIENTRY (*glMultiTexCoord2dvPtr)(int target, const double *v);
+static void APIENTRY (*glActiveTexturePtr)(int texture);
+
+void APIENTRY glMultiTexCoord2dv(int target, const double *v)
+{
+	glMultiTexCoord2dvPtr(target, v);
+}
+
+void APIENTRY glActiveTexture(int texture)
+{
+	glActiveTexturePtr(texture);
+}
+
+static void init_extensions(void)
+{
+	static gboolean init_done = FALSE;
+	if (init_done)
+		return;
+	init_done = TRUE;
+
+	g_debug("GtkGl: init_extensions");
+	const guchar *exts = NULL;
+	if (!(exts = glGetString(GL_EXTENSIONS)))
+		g_error("GtkGl: Unable to query extensions");
+	if (!(glMultiTexCoord2dvPtr = (void*)wglGetProcAddress("glMultiTexCoord2dvARB")))
+		g_error("GtkGl: Unable to load glMultiTexCoord2dv extension:\n%s", exts);
+	if (!(glActiveTexturePtr    = (void*)wglGetProcAddress("glActiveTextureARB")))
+		g_error("GtkGl: Unable to load glActiveTexture extension\n%s", exts);
+	g_debug("GtkGl: extensions - glMultiTexCoord2dvPtr=%p glActiveTexturePtr=%p",
+			glMultiTexCoord2dvPtr, glActiveTexturePtr);
+}
+
+/* gtkgl implementation */
 static void on_realize(GtkWidget *widget, gpointer _)
 {
 	g_debug("GtkGl: on_realize");
@@ -167,6 +203,7 @@ void gtk_gl_begin(GtkWidget *widget)
 	HGLRC hRC  = g_object_get_data(G_OBJECT(widget), "glcontext");
 	if (!wglMakeCurrent(hDC, hRC))
 		g_error("GtkGl: wglMakeCurrent failed");
+	init_extensions();
 }
 
 void gtk_gl_end(GtkWidget *widget)
@@ -186,7 +223,6 @@ void gtk_gl_disable(GtkWidget *widget)
 }
 
 
-
 /**************************
  * Mac OSX implementation *
  **************************/
diff --git a/src/objects/grits-marker.c b/src/objects/grits-marker.c
index 338cf1b..3bbaf79 100644
--- a/src/objects/grits-marker.c
+++ b/src/objects/grits-marker.c
@@ -35,6 +35,10 @@
 #include "gtkgl.h"
 #include "grits-marker.h"
 
+#ifdef SYS_WIN
+#include <GL/glext.h>
+#endif
+
 /* Texture setup functions */
 static void render_point(GritsMarker *marker)
 {
diff --git a/src/objects/grits-tile.c b/src/objects/grits-tile.c
index e2aeb45..61ed022 100644
--- a/src/objects/grits-tile.c
+++ b/src/objects/grits-tile.c
@@ -37,6 +37,11 @@
 #include "gtkgl.h"
 #include "grits-tile.h"
 
+#ifdef SYS_WIN
+#define GL_GLEXT_PROTOTYPES
+#include <GL/glext.h>
+#endif
+
 guint  grits_tile_mask = 0;
 
 gchar *grits_tile_path_table[2][2] = {