[grits] Add cube GtkGL example

[Andy Spencer <andys src gnome org>]

commit b711eb6b2129ffff4d2451e67cfe7b20138096f7
Author: Andy Spencer <andy753421 gmail com>
Date:   Wed Sep 18 08:34:52 2013 +0000

    Add cube GtkGL example

 examples/cube/cube.c   |   84 ++++++++++++++++++++++++++++++++++++++++++++++++
 examples/cube/makefile |   21 ++++++++++++
 2 files changed, 105 insertions(+), 0 deletions(-)
---
diff --git a/examples/cube/cube.c b/examples/cube/cube.c
new file mode 100644
index 0000000..80dd412
--- /dev/null
+++ b/examples/cube/cube.c
@@ -0,0 +1,84 @@
+#include <gtk/gtk.h>
+#include <GL/glut.h>
+#include "gtkgl.h"
+
+static gdouble rotate = 0;
+
+gboolean on_spin(GtkWidget *spin)
+{
+       /* Spin the cube when the toggle button is pressed */
+       if (gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(spin)))
+               rotate++;
+       gtk_widget_queue_draw(gtk_widget_get_toplevel(spin));
+       return TRUE;
+}
+
+gboolean on_draw(GtkWidget *draw)
+{
+       GtkAllocation alloc;
+       gtk_widget_get_allocation(draw, &alloc);
+
+       /* Start OpenGL Commands */
+       gtk_gl_begin(draw);
+
+       /* Setup View */
+       glViewport(0, 0, alloc.width, alloc.height);
+
+       glMatrixMode(GL_PROJECTION);
+       glLoadIdentity();
+       gluPerspective(45, (gdouble)alloc.width/alloc.height, 0.01, 10);
+
+       glMatrixMode(GL_MODELVIEW);
+       glLoadIdentity();
+       glTranslated(0, 0, -3);
+       glRotated(rotate+20, 1, 0, 0);
+       glRotated(rotate+30, 0, 1, 0);
+
+       /* Draw a Cube */
+       glClearColor(0, 0, 0.15, 0);
+       glClear(GL_COLOR_BUFFER_BIT);
+       glLineWidth(4);
+
+       glColor3f(1, 0, 0);
+       glutSolidCube(1);
+
+       glColor3f(1, 1, 1);
+       glutWireCube(1);
+
+       /* Done with OpenGL */
+       gtk_gl_end(draw);
+
+       return TRUE;
+}
+
+int main(int argc, char **argv)
+{
+       /* Library initialization */
+       gtk_init(&argc, &argv);
+       glutInit(&argc, argv);
+
+       /* Create widgets */
+       GtkWidget *win  = gtk_window_new(GTK_WINDOW_TOPLEVEL);
+       GtkWidget *box  = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
+       GtkWidget *draw = gtk_drawing_area_new();
+       GtkWidget *spin = gtk_toggle_button_new_with_label("Spin");
+
+       /* Pack everything together */
+       gtk_container_add(GTK_CONTAINER(win), box);
+       gtk_box_pack_start(GTK_BOX(box), draw, TRUE, TRUE, 0);
+       gtk_box_pack_start(GTK_BOX(box), spin, FALSE, FALSE, 0);
+
+       /* Connect signals */
+       g_signal_connect(win, "destroy", gtk_main_quit, NULL);
+       g_signal_connect(draw, "draw", G_CALLBACK(on_draw), NULL);
+       g_timeout_add(1000/60, (GSourceFunc)on_spin, spin);
+
+       /* Enable OpenGL on drawing frame */
+       gtk_gl_enable(draw);
+
+       /* Show and run main loop */
+       gtk_widget_show_all(win);
+       gtk_main();
+
+       return 0;
+}
diff --git a/examples/cube/makefile b/examples/cube/makefile
new file mode 100644
index 0000000..dc0b9df
--- /dev/null
+++ b/examples/cube/makefile
@@ -0,0 +1,21 @@
+CFLAGS    = -Wall -g
+CPPFLAGS  = -DSYS_X11
+LDFLAGS   = -lGL -lGLU -lglut
+
+CPPFLAGS += $(shell pkg-config --cflags gtk+-3.0)
+LDFLAGS  += $(shell pkg-config --libs   gtk+-3.0)
+
+CPPFLAGS += -I../../src
+VPATH     = ../../src
+
+test: cube
+       ./cube
+
+cube: cube.o gtkgl.o
+       gcc $(CFLAGS) -o $@ $+ $(LDFLAGS)
+
+%.o: %.c makefile
+       gcc $(CFLAGS) $(CPPFLAGS) -c -o $@ $<
+
+clean:
+       rm -f *.o cube