Use GLEW

git-svn-id: svn://cook.msm.cam.ac.uk:745/diff-tomo/dtr@283 bf6ca9ba-c028-0410-8290-897cf20841d1

7 files changed, 102 insertions, 88 deletions

diff --git a/configure.ac b/configure.ac
index 254bb61..832498b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -68,6 +68,9 @@ AM_PATH_GTKGLEXT_1_0(1.0.0,[echo "$GTKGLEXT_LIBS"],AC_MSG_ERROR([
  	*** gtkglext is required to build dtr; please make sure you have the
  	*** gtkglext development headers installed.]))
 
+AC_CHECK_LIB(GLEW, main, [GLEW_LIBS=-lGLEW; GLEW],  AC_MSG_ERROR([
+*** GLEW not found.  Do you have 'libglew-dev' or similar installed?]))
+
 AC_MSG_CHECKING([Cairo version 1.2.0])
 if $PKG_CONFIG --atleast-version 1.2.0 cairo ; then
 	CAIRO_VERSION=`$PKG_CONFIG --modversion cairo`
@@ -80,7 +83,7 @@ else
 fi
 
 CFLAGS="$CFLAGS $CAIRO_CFLAGS $LIBPNG_CLAGS"
-LIBS="$LIBS $CAIRO_LIBS $LIBPNG_LIBS"
+LIBS="$LIBS $CAIRO_LIBS $LIBPNG_LIBS $GLEW_LIBS"
 
 AC_OUTPUT(Makefile src/Makefile data/Makefile)
 
diff --git a/src/Makefile.am b/src/Makefile.am
index 5b99a9f..117b738 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -12,5 +12,5 @@ refinetest3d_SOURCES = refinetest3d.c reflections.c basis.c utils.c reproject.c
 refinetest3d_LDADD = @LIBS@ @GTK_LIBS@ -lm -lgsl -lgslcblas -lutil
 
 AM_CFLAGS = -Wall -g @CFLAGS@ @GTK_CFLAGS@ @GTKGLEXT_CFLAGS@
-AM_CPPFLAGS = -DDATADIR=\""$(datadir)"\"
+AM_CPPFLAGS = -DDATADIR=\""$(datadir)"\" -I/usr/include/GL
 
diff --git a/src/control.h b/src/control.h
index 2893d5c..4b97970 100644
--- a/src/control.h
+++ b/src/control.h
@@ -18,7 +18,6 @@
 
 #include <gtk/gtk.h>
 #include <inttypes.h>
-#include <GL/gl.h>
 
 typedef enum ift_enum {
 	INPUT_NONE,
diff --git a/src/displaywindow.c b/src/displaywindow.c
index 5bd00fc..a038c8c 100644
--- a/src/displaywindow.c
+++ b/src/displaywindow.c
@@ -20,10 +20,7 @@
 #include <math.h>
 #include <gdk/gdkgl.h>
 #include <gtk/gtkgl.h>
-#define GL_GLEXT_PROTOTYPES 1
-#include <GL/gl.h>
-#include <GL/glext.h>
-#include <GL/glu.h>
+#include <glew.h>
 
 #include "trackball.h"
 #include "reflections.h"
@@ -558,6 +555,7 @@ DisplayWindow *displaywindow_open(ControlContext *ctx) {
 	ctx->dw = dw;
 	
 	dw->gl_use_buffers = 1;
+	dw->gl_use_shaders = 1;
 	dw->view = DW_ORTHO;
 	dw->mode = DW_MAPPED;
 	dw->distance = 150;
@@ -594,6 +592,7 @@ DisplayWindow *displaywindow_open(ControlContext *ctx) {
 		fprintf(stderr, "Can't find double-buffered visual.\n");
 		exit(1);
 	}
+	
 	gtk_container_set_reallocate_redraws(GTK_CONTAINER(dw->window), TRUE);
 	dw->drawing_area = gtk_drawing_area_new();
 	gtk_widget_set_size_request(dw->drawing_area, 640, 640);
diff --git a/src/displaywindow.h b/src/displaywindow.h
index baab13d..d0173f4 100644
--- a/src/displaywindow.h
+++ b/src/displaywindow.h
@@ -17,7 +17,7 @@
 #define DISPLAYWINDOW_H
 
 #include <gtk/gtk.h>
-#include <GL/gl.h>
+#include <glew.h>
 
 #include "control.h"
 
@@ -46,6 +46,7 @@ typedef struct dw_struct {
 	/* Low-level OpenGL stuff */
 	GLuint			gl_list_id;			/* Display list for "everything else" */
 	int			gl_use_buffers;			/* 0=use vertex arrays only, otherwise use VBOs */
+	int			gl_use_shaders;			/* 1 = use shaders */
 	GLuint			gl_ref_vertex_buffer;		/* "Measured reflection" stuff */
 	GLfloat			*gl_ref_vertex_array;
 	GLuint			gl_ref_normal_buffer;
@@ -64,9 +65,9 @@ typedef struct dw_struct {
 	GLuint			gl_line_vertex_buffer;		/* Indexing line stuff */
 	GLfloat			*gl_line_vertex_array;
 	GLsizei			gl_line_num_vertices;
-	GLhandleARB		gl_vshader_lightpp;
-	GLhandleARB		gl_fshader_lightpp;
-	GLhandleARB		gl_program_lightpp;
+	GLuint			gl_vshader_lightpp;
+	GLuint			gl_fshader_lightpp;
+	GLuint			gl_program_lightpp;
 	
 	/* Display parameters */
 	DisplayWindowView	view;
diff --git a/src/glbits.c b/src/glbits.c
index b489ea6..d32fc0c 100644
--- a/src/glbits.c
+++ b/src/glbits.c
@@ -13,13 +13,10 @@
 #include <config.h>
 #endif
 
+#include <glew.h>
 #include <gtk/gtk.h>
 #include <gdk/gdkgl.h>
 #include <gtk/gtkgl.h>
-#define GL_GLEXT_PROTOTYPES 1
-#include <GL/gl.h>
-#include <GL/glext.h>
-#include <GL/glu.h>
 #include <math.h>
 #include <stdlib.h>
 
@@ -30,25 +27,35 @@
 #include "utils.h"
 
 /* Utility function to load and compile a shader, checking the info log */
-static GLhandleARB glbits_load_shader(const char *filename, GLenum type) {
+static GLuint glbits_load_shader(const char *filename, GLenum type) {
 
-	GLhandleARB shader;
+	GLuint shader;
 	char text[4096];
 	size_t len;
 	FILE *fh;
 	int l;
+	GLint status;
 	
 	fh = fopen(filename, "r");
+	if ( fh == NULL ) {
+		fprintf(stderr, "Couldn't load shader '%s'\n", filename);
+		return 0;
+	}
 	len = fread(text, 1, 4095, fh);
 	fclose(fh);
 	text[len] = '\0';
-	const GLcharARB *source = text;
-	shader = glCreateShaderObjectARB(type);
-	glShaderSourceARB(shader, 1, &source, NULL);
-	glCompileShaderARB(shader);
-	glGetInfoLogARB(shader, 4095, &l, text);
-	if ( l > 0 ) {
-		printf("%s\n", text); fflush(stdout);
+	const GLchar *source = text;
+	shader = glCreateShader(type);
+	glShaderSource(shader, 1, &source, NULL);
+	glCompileShader(shader);
+	glGetShaderiv(shader, GL_COMPILE_STATUS, &status); 
+	if ( status == GL_FALSE ) {
+		glGetShaderInfoLog(shader, 4095, &l, text);
+		if ( l > 0 ) {
+			printf("%s\n", text); fflush(stdout);
+		} else {
+			printf("Shader compilation failed.\n");
+		}
 	}
 	
 	return shader;
@@ -58,21 +65,21 @@ static GLhandleARB glbits_load_shader(const char *filename, GLenum type) {
 static void glbits_load_shaders(DisplayWindow *dw) {
 	
 	/* Lighting-per-fragment */
-	dw->gl_vshader_lightpp = glbits_load_shader(DATADIR"/dtr/light-pp.vert", GL_VERTEX_SHADER_ARB);
-	dw->gl_fshader_lightpp = glbits_load_shader(DATADIR"/dtr/light-pp.frag", GL_FRAGMENT_SHADER_ARB);
-	dw->gl_program_lightpp = glCreateProgramObjectARB();
-	glAttachObjectARB(dw->gl_program_lightpp, dw->gl_vshader_lightpp);
-	glAttachObjectARB(dw->gl_program_lightpp, dw->gl_fshader_lightpp);
-	glLinkProgramARB(dw->gl_program_lightpp);
+	dw->gl_vshader_lightpp = glbits_load_shader(DATADIR"/dtr/light-pp.vert", GL_VERTEX_SHADER);
+	dw->gl_fshader_lightpp = glbits_load_shader(DATADIR"/dtr/light-pp.frag", GL_FRAGMENT_SHADER);
+	dw->gl_program_lightpp = glCreateProgram();
+	glAttachShader(dw->gl_program_lightpp, dw->gl_vshader_lightpp);
+	glAttachShader(dw->gl_program_lightpp, dw->gl_fshader_lightpp);
+	glLinkProgram(dw->gl_program_lightpp);
 	
 }
 
 static void glbits_delete_shaders(DisplayWindow *dw) {
 
-	glDetachObjectARB(dw->gl_program_lightpp, dw->gl_fshader_lightpp);
-	glDetachObjectARB(dw->gl_program_lightpp, dw->gl_vshader_lightpp);
-	glDeleteObjectARB(dw->gl_fshader_lightpp);
-	glDeleteObjectARB(dw->gl_program_lightpp);
+	glDetachShader(dw->gl_program_lightpp, dw->gl_fshader_lightpp);
+	glDetachShader(dw->gl_program_lightpp, dw->gl_vshader_lightpp);
+	glDeleteShader(dw->gl_fshader_lightpp);
+	glDeleteShader(dw->gl_program_lightpp);
 
 }
 
@@ -160,8 +167,8 @@ void glbits_prepare(DisplayWindow *dw) {
 	
 	/* "Measured" reflections */
 	if ( dw->gl_use_buffers ) {
-		glGenBuffersARB(1, &dw->gl_ref_vertex_buffer);
-		glGenBuffersARB(1, &dw->gl_ref_normal_buffer);
+		glGenBuffers(1, &dw->gl_ref_vertex_buffer);
+		glGenBuffers(1, &dw->gl_ref_normal_buffer);
 	}
 	reflection = ctx->reflectionlist->reflections;
 	i = 0;
@@ -188,11 +195,11 @@ void glbits_prepare(DisplayWindow *dw) {
 			reflection = reflection->next;
 		};	
 		if ( dw->gl_use_buffers ) {
-			glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_ref_vertex_buffer);
-			glBufferDataARB(GL_ARRAY_BUFFER, 3*dw->gl_ref_num_vertices*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
+			glBindBuffer(GL_ARRAY_BUFFER, dw->gl_ref_vertex_buffer);
+			glBufferData(GL_ARRAY_BUFFER, 3*dw->gl_ref_num_vertices*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
 			free(vertices);
-			glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_ref_normal_buffer);
-			glBufferDataARB(GL_ARRAY_BUFFER, 3*dw->gl_ref_num_vertices*sizeof(GLfloat), normals, GL_STATIC_DRAW);
+			glBindBuffer(GL_ARRAY_BUFFER, dw->gl_ref_normal_buffer);
+			glBufferData(GL_ARRAY_BUFFER, 3*dw->gl_ref_num_vertices*sizeof(GLfloat), normals, GL_STATIC_DRAW);
 			free(normals);
 		} else {
 			dw->gl_ref_vertex_array = vertices;
@@ -202,8 +209,8 @@ void glbits_prepare(DisplayWindow *dw) {
 	
 	/* Marker "reflections" */
 	if ( dw->gl_use_buffers ) {
-		glGenBuffersARB(1, &dw->gl_marker_vertex_buffer);
-		glGenBuffersARB(1, &dw->gl_marker_normal_buffer);
+		glGenBuffers(1, &dw->gl_marker_vertex_buffer);
+		glGenBuffers(1, &dw->gl_marker_normal_buffer);
 	}
 	reflection = ctx->reflectionlist->reflections;
 	i = 0;
@@ -225,11 +232,11 @@ void glbits_prepare(DisplayWindow *dw) {
 			reflection = reflection->next;
 		};	
 		if ( dw->gl_use_buffers ) {
-			glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_marker_vertex_buffer);
-			glBufferDataARB(GL_ARRAY_BUFFER, 3*dw->gl_marker_num_vertices*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
+			glBindBuffer(GL_ARRAY_BUFFER, dw->gl_marker_vertex_buffer);
+			glBufferData(GL_ARRAY_BUFFER, 3*dw->gl_marker_num_vertices*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
 			free(vertices);
-			glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_marker_normal_buffer);
-			glBufferDataARB(GL_ARRAY_BUFFER, 3*dw->gl_marker_num_vertices*sizeof(GLfloat), normals, GL_STATIC_DRAW);
+			glBindBuffer(GL_ARRAY_BUFFER, dw->gl_marker_normal_buffer);
+			glBufferData(GL_ARRAY_BUFFER, 3*dw->gl_marker_num_vertices*sizeof(GLfloat), normals, GL_STATIC_DRAW);
 			free(normals);
 		} else {
 			dw->gl_marker_vertex_array = vertices;
@@ -239,8 +246,8 @@ void glbits_prepare(DisplayWindow *dw) {
 	
 	/* Generated reflections */
 	if ( dw->gl_use_buffers ) {
-		glGenBuffersARB(1, &dw->gl_gen_vertex_buffer);
-		glGenBuffersARB(1, &dw->gl_gen_normal_buffer);
+		glGenBuffers(1, &dw->gl_gen_vertex_buffer);
+		glGenBuffers(1, &dw->gl_gen_normal_buffer);
 	}
 	if ( ctx->integrated != NULL ) {
 		reflection = ctx->integrated->reflections;
@@ -261,13 +268,13 @@ void glbits_prepare(DisplayWindow *dw) {
 				reflection = reflection->next;
 			};	
 			if ( dw->gl_use_buffers ) {
-				glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_gen_vertex_buffer);
-				glBufferDataARB(GL_ARRAY_BUFFER, 3*dw->gl_gen_num_vertices*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
+				glBindBuffer(GL_ARRAY_BUFFER, dw->gl_gen_vertex_buffer);
+				glBufferData(GL_ARRAY_BUFFER, 3*dw->gl_gen_num_vertices*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
 				free(vertices);
-				glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_gen_normal_buffer);
-				glBufferDataARB(GL_ARRAY_BUFFER, 3*dw->gl_gen_num_vertices*sizeof(GLfloat), normals, GL_STATIC_DRAW);
+				glBindBuffer(GL_ARRAY_BUFFER, dw->gl_gen_normal_buffer);
+				glBufferData(GL_ARRAY_BUFFER, 3*dw->gl_gen_num_vertices*sizeof(GLfloat), normals, GL_STATIC_DRAW);
 				free(normals);
-				glBindBufferARB(GL_ARRAY_BUFFER, 0);	/* ************* */
+				glBindBuffer(GL_ARRAY_BUFFER, 0);	/* ************* */
 			} else {
 				dw->gl_gen_vertex_array = vertices;
 				dw->gl_gen_normal_array = normals;
@@ -288,7 +295,7 @@ void glbits_prepare(DisplayWindow *dw) {
 		dw->gl_line_num_vertices = 3*2*((2*1+1)*(2*1+1));
 		
 		if ( dw->gl_use_buffers ) {
-			glGenBuffersARB(1, &dw->gl_line_vertex_buffer);
+			glGenBuffers(1, &dw->gl_line_vertex_buffer);
 		}
 		reflection = ctx->reflectionlist->reflections;
 		vertices = malloc(3*dw->gl_line_num_vertices*sizeof(GLfloat));
@@ -336,8 +343,8 @@ void glbits_prepare(DisplayWindow *dw) {
 		}
 		
 		if ( dw->gl_use_buffers ) {
-			glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_line_vertex_buffer);
-			glBufferDataARB(GL_ARRAY_BUFFER, 3*dw->gl_line_num_vertices*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
+			glBindBuffer(GL_ARRAY_BUFFER, dw->gl_line_vertex_buffer);
+			glBufferData(GL_ARRAY_BUFFER, 3*dw->gl_line_num_vertices*sizeof(GLfloat), vertices, GL_STATIC_DRAW);
 			free(vertices);
 		} else {
 			dw->gl_line_vertex_array = vertices;
@@ -714,7 +721,8 @@ gint glbits_expose(GtkWidget *widget, GdkEventExpose *event, DisplayWindow *dw)
 	glTranslatef(dw->x_pos, -dw->y_pos, 400.0-dw->distance);
 	build_rotmatrix(m, dw->view_quat);
 	glMultMatrixf(&m[0][0]);
-	
+
+	/* begin suspect block */
 	glPushClientAttrib(GL_CLIENT_VERTEX_ARRAY_BIT);
 	glEnableClientState(GL_VERTEX_ARRAY);
 	glEnableClientState(GL_NORMAL_ARRAY);
@@ -726,7 +734,7 @@ gint glbits_expose(GtkWidget *widget, GdkEventExpose *event, DisplayWindow *dw)
 			
 			GLfloat att[] = {1.0, 1.0, 0.0};
 			
-			glPointParameterfvARB(GL_POINT_DISTANCE_ATTENUATION, att);
+			glPointParameterfv(GL_POINT_DISTANCE_ATTENUATION, att);
 			glPointSize(20.0);
 			glEnable(GL_POINT_SMOOTH);
 			
@@ -737,12 +745,12 @@ gint glbits_expose(GtkWidget *widget, GdkEventExpose *event, DisplayWindow *dw)
 			glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 0.0);
 			
 			if ( dw->gl_use_buffers ) {
-				glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_ref_vertex_buffer);
+				glBindBuffer(GL_ARRAY_BUFFER, dw->gl_ref_vertex_buffer);
 				glVertexPointer(3, GL_FLOAT, 0, NULL);
-				glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_ref_normal_buffer);
+				glBindBuffer(GL_ARRAY_BUFFER, dw->gl_ref_normal_buffer);
 				glNormalPointer(GL_FLOAT, 0, NULL);
 				glDrawArrays(GL_POINTS, 0, dw->gl_ref_num_vertices);
-				glBindBufferARB(GL_ARRAY_BUFFER, 0);
+				glBindBuffer(GL_ARRAY_BUFFER, 0);
 			} else {
 				glVertexPointer(3, GL_FLOAT, 0, dw->gl_ref_vertex_array);
 				glNormalPointer(GL_FLOAT, 0, dw->gl_ref_normal_array);
@@ -763,12 +771,12 @@ gint glbits_expose(GtkWidget *widget, GdkEventExpose *event, DisplayWindow *dw)
 			glColor3f(0.0, 0.0, 1.0);
 			
 			if ( dw->gl_use_buffers ) {
-				glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_marker_vertex_buffer);
+				glBindBuffer(GL_ARRAY_BUFFER, dw->gl_marker_vertex_buffer);
 				glVertexPointer(3, GL_FLOAT, 0, NULL);
-				glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_marker_normal_buffer);
+				glBindBuffer(GL_ARRAY_BUFFER, dw->gl_marker_normal_buffer);
 				glNormalPointer(GL_FLOAT, 0, NULL);
 				glDrawArrays(GL_QUADS, 0, dw->gl_marker_num_vertices);
-				glBindBufferARB(GL_ARRAY_BUFFER, 0);
+				glBindBuffer(GL_ARRAY_BUFFER, 0);
 			} else {
 				glVertexPointer(3, GL_FLOAT, 0, dw->gl_marker_vertex_array);
 				glNormalPointer(GL_FLOAT, 0, dw->gl_marker_normal_array);
@@ -788,25 +796,24 @@ gint glbits_expose(GtkWidget *widget, GdkEventExpose *event, DisplayWindow *dw)
 			glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, 100.0);
 			glColor3f(0.7, 0.7, 0.0);
 			
-			glUseProgramObjectARB(dw->gl_program_lightpp);
+			if ( dw->gl_use_shaders ) glUseProgram(dw->gl_program_lightpp);
 			if ( dw->gl_use_buffers ) {
-				glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_gen_vertex_buffer);
+				glBindBuffer(GL_ARRAY_BUFFER, dw->gl_gen_vertex_buffer);
 				glVertexPointer(3, GL_FLOAT, 0, NULL);
-				glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_gen_normal_buffer);
+				glBindBuffer(GL_ARRAY_BUFFER, dw->gl_gen_normal_buffer);
 				glNormalPointer(GL_FLOAT, 0, NULL);
 				glDrawArrays(GL_QUADS, 0, dw->gl_gen_num_vertices);
-				glBindBufferARB(GL_ARRAY_BUFFER, 0);
+				glBindBuffer(GL_ARRAY_BUFFER, 0);
 			} else {
 				glVertexPointer(3, GL_FLOAT, 0, dw->gl_gen_vertex_array);
 				glNormalPointer(GL_FLOAT, 0, dw->gl_gen_normal_array);
 				glDrawArrays(GL_QUADS, 0, dw->gl_gen_num_vertices);
 			}
-			glUseProgramObjectARB(0);
+			if ( dw->gl_use_shaders ) glUseProgram(0);
 			
 		}
 	
 	}
-	
 	glDisable(GL_NORMAL_ARRAY);
 	
 	/* Draw indexing lines */
@@ -817,10 +824,10 @@ gint glbits_expose(GtkWidget *widget, GdkEventExpose *event, DisplayWindow *dw)
 		glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, black);
 		
 		if ( dw->gl_use_buffers ) {
-			glBindBufferARB(GL_ARRAY_BUFFER, dw->gl_line_vertex_buffer);
+			glBindBuffer(GL_ARRAY_BUFFER, dw->gl_line_vertex_buffer);
 			glVertexPointer(3, GL_FLOAT, 0, NULL);
 			glDrawArrays(GL_LINES, 0, dw->gl_line_num_vertices);
-			glBindBufferARB(GL_ARRAY_BUFFER, 0);
+			glBindBuffer(GL_ARRAY_BUFFER, 0);
 		} else {
 			glVertexPointer(3, GL_FLOAT, 0, dw->gl_line_vertex_array);
 			glDrawArrays(GL_LINES, 0, dw->gl_line_num_vertices);
@@ -880,21 +887,21 @@ gboolean glbits_configure(GtkWidget *widget, GdkEventConfigure *event, DisplayWi
 void glbits_free_resources(DisplayWindow *dw) {
 
 	if ( dw->gl_use_buffers ) {
-		glDeleteBuffersARB(1, &dw->gl_ref_vertex_buffer);
-		glDeleteBuffersARB(1, &dw->gl_ref_normal_buffer);
-		glDeleteBuffersARB(1, &dw->gl_marker_vertex_buffer);
-		glDeleteBuffersARB(1, &dw->gl_marker_normal_buffer);
-		glDeleteBuffersARB(1, &dw->gl_gen_vertex_buffer);
-		glDeleteBuffersARB(1, &dw->gl_gen_normal_buffer);
-		glDeleteBuffersARB(1, &dw->gl_line_vertex_buffer);
+		glDeleteBuffers(1, &dw->gl_ref_vertex_buffer);
+		glDeleteBuffers(1, &dw->gl_ref_normal_buffer);
+		glDeleteBuffers(1, &dw->gl_marker_vertex_buffer);
+		glDeleteBuffers(1, &dw->gl_marker_normal_buffer);
+		glDeleteBuffers(1, &dw->gl_gen_vertex_buffer);
+		glDeleteBuffers(1, &dw->gl_gen_normal_buffer);
+		glDeleteBuffers(1, &dw->gl_line_vertex_buffer);
 	} else {
-		free(dw->gl_ref_vertex_array);
-		free(dw->gl_ref_normal_array);
-		free(dw->gl_marker_vertex_array);
-		free(dw->gl_marker_normal_array);
-		free(dw->gl_gen_vertex_array);
-		free(dw->gl_gen_normal_array);
-		free(dw->gl_line_vertex_array);
+		if ( dw->gl_ref_vertex_array != NULL ) free(dw->gl_ref_vertex_array);
+		if ( dw->gl_ref_normal_array != NULL ) free(dw->gl_ref_normal_array);
+		if ( dw->gl_marker_vertex_array != NULL ) free(dw->gl_marker_vertex_array);
+		if ( dw->gl_marker_normal_array != NULL ) free(dw->gl_marker_normal_array);
+		if ( dw->gl_gen_vertex_array != NULL ) free(dw->gl_gen_vertex_array);
+		if ( dw->gl_gen_normal_array != NULL ) free(dw->gl_gen_normal_array);
+		if ( dw->gl_line_vertex_array != NULL ) free(dw->gl_line_vertex_array);
 	}
 	glDeleteLists(dw->gl_list_id, 1);
 	
@@ -902,12 +909,12 @@ void glbits_free_resources(DisplayWindow *dw) {
 
 void glbits_final_free_resources(DisplayWindow *dw) {
 	glbits_free_resources(dw);
-	glbits_delete_shaders(dw);
+	if ( dw->gl_use_shaders ) glbits_delete_shaders(dw);
 }
 
 static void glbits_first_prepare(DisplayWindow *dw) {
 	glbits_prepare(dw);
-	glbits_load_shaders(dw);
+	if ( dw->gl_use_shaders ) glbits_load_shaders(dw);
 }
 
 gint glbits_realise(GtkWidget *widget, DisplayWindow *dw) {
@@ -921,6 +928,10 @@ gint glbits_realise(GtkWidget *widget, DisplayWindow *dw) {
 		return 0;
 	}
 	
+	/* This has to be done once an OpenGL context has been created */
+	GLenum glew_err = glewInit();
+	if (glew_err != GLEW_OK) fprintf(stderr, "GLEW initialisation error: %s\n", glewGetErrorString(glew_err));
+		
 	glbits_set_ortho(dw, w, h);
 	glbits_first_prepare(dw);
 	
diff --git a/src/main.c b/src/main.c
index b83e209..6259818 100644
--- a/src/main.c
+++ b/src/main.c
@@ -23,6 +23,7 @@
 #include <gdk/gdkgl.h>
 #include <gtk/gtkgl.h>
 #include <sys/stat.h>
+#include <glew.h>
 
 #include "displaywindow.h"
 #include "reflections.h"