[grits] Add convex tessellation example

[Andy Spencer <andys src gnome org>]

commit ae7b2d9e5f5bae86f1d50ee68c8dee109a66ed5f
Author: Andy Spencer <andy753421 gmail com>
Date:   Mon Jan 24 03:23:40 2011 +0000

    Add convex tessellation example
    
    This tessellates a non-convex polygon such that it can be drawn
    correctly.

 examples/.gitignore    |    1 +
 examples/tess/convex.c |  127 ++++++++++++++++++++++++++++++++++++++++++++++++
 examples/tess/mkfile   |    4 +-
 3 files changed, 130 insertions(+), 2 deletions(-)
---
diff --git a/examples/.gitignore b/examples/.gitignore
index 420b021..0f06fc9 100644
--- a/examples/.gitignore
+++ b/examples/.gitignore
@@ -6,5 +6,6 @@ interp/interp
 plugin/teapot
 shader/shader
 sort/sort
+tess/convex
 tess/split
 tex/tex
diff --git a/examples/tess/convex.c b/examples/tess/convex.c
new file mode 100644
index 0000000..7d8451d
--- /dev/null
+++ b/examples/tess/convex.c
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2010 Andy Spencer <andy753421 gmail com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <math.h>
+#include <gtk/gtk.h>
+#include <gtk/gtkgl.h>
+#include <gdk/gdkkeysyms.h>
+#include <GL/gl.h>
+#include <GL/glu.h>
+
+guint tex, texl, texr;
+
+gboolean on_key_press(GtkWidget *widget, GdkEventKey *event, gpointer _)
+{
+	if (event->keyval == GDK_q)
+		gtk_main_quit();
+	return FALSE;
+}
+
+gboolean on_expose(GtkWidget *drawing, GdkEventExpose *event, gpointer _)
+{
+	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+	glMatrixMode(GL_PROJECTION);
+	glLoadIdentity();
+	glOrtho(-1,1, -1,1, 10,-10);
+	glMatrixMode(GL_MODELVIEW);
+	glLoadIdentity();
+	glTranslatef(0, 0, -5);
+
+	glEnable(GL_COLOR_MATERIAL);
+	glDisable(GL_TEXTURE_2D);
+	glColor3f(1.0, 1.0, 1.0);
+
+	/* Create vertexes */
+	double verts[20][3];
+	for (int i = 0; i < G_N_ELEMENTS(verts); i++) {
+		float ang = 2*G_PI * i / G_N_ELEMENTS(verts);
+		verts[i][0] = sin(ang) * (i%2+0.5) * 0.6;
+		verts[i][1] = cos(ang) * (i%2+0.5) * 0.6;
+		verts[i][2] = 0;
+	}
+
+	/* Draw raw polygon */
+	glColor4f(0.5, 0.0, 0.0, 1.0);
+	GLUtesselator *tess = gluNewTess();
+	gluTessCallback(tess, GLU_TESS_BEGIN,  glBegin);
+	gluTessCallback(tess, GLU_TESS_VERTEX, glVertex3dv);
+	gluTessCallback(tess, GLU_TESS_END,    glEnd);
+	gluTessBeginPolygon(tess, NULL);
+	gluTessBeginContour(tess);
+	for (int i = 0; i < G_N_ELEMENTS(verts); i++)
+		gluTessVertex(tess, verts[i], verts[i]);
+	gluTessEndContour(tess);
+	gluTessEndPolygon(tess);
+	gluDeleteTess(tess);
+
+	/* Draw tesselated polygon */
+	//glColor4f(0.0, 0.0, 0.5, 1.0);
+	//glBegin(GL_POLYGON);
+	//for (int i = 0; i < G_N_ELEMENTS(verts); i++)
+	//	glVertex3dv(verts[i]);
+	//glEnd();
+
+	/* Draw outline */
+	glColor4f(0.8, 0.8, 0.8, 1.0);
+	glBegin(GL_LINE_LOOP);
+	for (int i = 0; i < G_N_ELEMENTS(verts); i++)
+		glVertex3dv(verts[i]);
+	glEnd();
+
+	/* Flush */
+	GdkGLDrawable *gldrawable = gdk_gl_drawable_get_current();
+	if (gdk_gl_drawable_is_double_buffered(gldrawable))
+		gdk_gl_drawable_swap_buffers(gldrawable);
+	else
+		glFlush();
+	return FALSE;
+}
+gboolean on_configure(GtkWidget *drawing, GdkEventConfigure *event, gpointer _)
+{
+	glViewport(0, 0,
+		drawing->allocation.width,
+		drawing->allocation.height);
+	return FALSE;
+}
+
+int main(int argc, char **argv)
+{
+	gtk_init(&argc, &argv);
+
+	GtkWidget   *window   = gtk_window_new(GTK_WINDOW_TOPLEVEL);
+	GtkWidget   *drawing  = gtk_drawing_area_new();
+	GdkGLConfig *glconfig = gdk_gl_config_new_by_mode((GdkGLConfigMode)(
+			GDK_GL_MODE_RGBA   | GDK_GL_MODE_DEPTH |
+			GDK_GL_MODE_DOUBLE | GDK_GL_MODE_ALPHA));
+	g_signal_connect(window,  "destroy",         G_CALLBACK(gtk_main_quit), NULL);
+	g_signal_connect(window,  "key-press-event", G_CALLBACK(on_key_press),  NULL);
+	g_signal_connect(drawing, "expose-event",    G_CALLBACK(on_expose),     NULL);
+	g_signal_connect(drawing, "configure-event", G_CALLBACK(on_configure),  NULL);
+	gtk_widget_set_gl_capability(drawing, glconfig, NULL, TRUE, GDK_GL_RGBA_TYPE);
+	gtk_container_add(GTK_CONTAINER(window), drawing);
+	gtk_widget_show_all(window);
+
+	/* OpenGL setup */
+	GdkGLContext  *glcontext  = gtk_widget_get_gl_context(GTK_WIDGET(drawing));
+	GdkGLDrawable *gldrawable = gtk_widget_get_gl_drawable(GTK_WIDGET(drawing));
+	gdk_gl_drawable_gl_begin(gldrawable, glcontext);
+
+	/* Go */
+	gtk_main();
+	gdk_gl_drawable_gl_end(gldrawable);
+}
diff --git a/examples/tess/mkfile b/examples/tess/mkfile
index 53cc145..142ca46 100644
--- a/examples/tess/mkfile
+++ b/examples/tess/mkfile
@@ -1,5 +1,5 @@
 MKSHELL=/usr/lib/plan9/bin/rc
-PROGS=split
+PROGS=convex split
 PKGS=gtkglext-1.0
-default:V: split-run
+default:V: convex-run
 <$HOME/lib/mkcommon