/*
* Copyright (C) 1999-2001 Brian Paul All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
* AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/*
* Ported to GLES2.
* Kristian Høgsberg <krh@bitplanet.net>
* May 3, 2010
*
* Improve GLES2 port:
* * Refactor gear drawing.
* * Use correct normals for surfaces.
* * Improve shader.
* * Use perspective projection transformation.
* * Add FPS count.
* * Add comments.
* Alexandros Frantzis <alexandros.frantzis@linaro.org>
* Jul 13, 2010
*/
#define GL_GLEXT_PROTOTYPES
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/time.h>
#include <unistd.h>
#include <GLES2/gl2.h>
#include <cogl/cogl.h>
#include <cogl/cogl-gles2.h>
#include <glib.h>
#define STRIPS_PER_TOOTH 7
#define VERTICES_PER_TOOTH 34
#define GEAR_VERTEX_STRIDE 6
typedef struct _Data
{
CoglContext *ctx;
CoglFramebuffer *fb;
CoglGLES2Context *gles2_ctx;
GTimer *timer;
int frames;
double last_elapsed;
} Data;
/**
* Struct describing the vertices in triangle strip
*/
struct vertex_strip {
/** The first vertex in the strip */
GLint first;
/** The number of consecutive vertices in the strip after the first */
GLint count;
};
/* Each vertex consist of GEAR_VERTEX_STRIDE GLfloat attributes */
typedef GLfloat GearVertex[GEAR_VERTEX_STRIDE];
/**
* Struct representing a gear.
*/
struct gear {
/** The array of vertices comprising the gear */
GearVertex *vertices;
/** The number of vertices comprising the gear */
int nvertices;
/** The array of triangle strips comprising the gear */
struct vertex_strip *strips;
/** The number of triangle strips comprising the gear */
int nstrips;
/** The Vertex Buffer Object holding the vertices in the graphics card */
GLuint vbo;
};
/** The view rotation [x, y, z] */
static GLfloat view_rot[3] = { 20.0, 30.0, 0.0 };
/** The gears */
static struct gear *gear1, *gear2, *gear3;
/** The current gear rotation angle */
static GLfloat angle = 0.0;
/** The location of the shader uniforms */
static GLuint ModelViewProjectionMatrix_location,
NormalMatrix_location,
LightSourcePosition_location,
MaterialColor_location;
/** The projection matrix */
static GLfloat ProjectionMatrix[16];
/** The direction of the directional light for the scene */
static const GLfloat LightSourcePosition[4] = { 5.0, 5.0, 10.0, 1.0};
/**
* Fills a gear vertex.
*
* @param v the vertex to fill
* @param x the x coordinate
* @param y the y coordinate
* @param z the z coortinate
* @param n pointer to the normal table
*
* @return the operation error code
*/
static GearVertex *
vert (GearVertex *v, GLfloat x, GLfloat y, GLfloat z, GLfloat n[3])
{
v[0][0] = x;
v[0][1] = y;
v[0][2] = z;
v[0][3] = n[0];
v[0][4] = n[1];
v[0][5] = n[2];
return v + 1;
}
/**
* Create a gear wheel.
*
* @param inner_radius radius of hole at center
* @param outer_radius radius at center of teeth
* @param width width of gear
* @param teeth number of teeth
* @param tooth_depth depth of tooth
*
* @return pointer to the constructed struct gear
*/
static struct gear *
create_gear (GLfloat inner_radius, GLfloat outer_radius, GLfloat width,
GLint teeth, GLfloat tooth_depth)
{
GLfloat r0, r1, r2;
GLfloat da;
GearVertex *v;
struct gear *gear;
double s[5], c[5];
GLfloat normal[3];
int cur_strip = 0;
int i;
/* Allocate memory for the gear */
gear = malloc (sizeof *gear);
if (gear == NULL)
return NULL;
/* Calculate the radii used in the gear */
r0 = inner_radius;
r1 = outer_radius - tooth_depth / 2.0;
r2 = outer_radius + tooth_depth / 2.0;
da = 2.0 * M_PI / teeth / 4.0;
/* Allocate memory for the triangle strip information */
gear->nstrips = STRIPS_PER_TOOTH * teeth;
gear->strips = calloc (gear->nstrips, sizeof (*gear->strips));
/* Allocate memory for the vertices */
gear->vertices = calloc (VERTICES_PER_TOOTH * teeth, sizeof(*gear->vertices));
v = gear->vertices;
for (i = 0; i < teeth; i++) {
/* Calculate needed sin/cos for varius angles */
sincos (i * 2.0 * M_PI / teeth, &s[0], &c[0]);
sincos (i * 2.0 * M_PI / teeth + da, &s[1], &c[1]);
sincos (i * 2.0 * M_PI / teeth + da * 2, &s[2], &c[2]);
sincos (i * 2.0 * M_PI / teeth + da * 3, &s[3], &c[3]);
sincos (i * 2.0 * M_PI / teeth + da * 4, &s[4], &c[4]);
/* A set of macros for making the creation of the gears easier */
#define GEAR_POINT(r, da) { (r) * c[(da)], (r) * s[(da)] }
#define SET_NORMAL(x, y, z) do { \
normal[0] = (x); normal[1] = (y); normal[2] = (z); \
} while(0)
#define GEAR_VERT(v, point, sign) vert((v), p[(point)].x, p[(point)].y, (sign) * width * 0.5, normal)
#define START_STRIP do { \
gear->strips[cur_strip].first = v - gear->vertices; \
} while(0);
#define END_STRIP do { \
int _tmp = (v - gear->vertices); \
gear->strips[cur_strip].count = _tmp - gear->strips[cur_strip].first; \
cur_strip++; \
} while (0)
#define QUAD_WITH_NORMAL(p1, p2) do { \
SET_NORMAL((p[(p1)].y - p[(p2)].y), -(p[(p1)].x - p[(p2)].x), 0); \
v = GEAR_VERT(v, (p1), -1); \
v = GEAR_VERT(v, (p1), 1); \
v = GEAR_VERT(v, (p2), -1); \
v = GEAR_VERT(v, (p2), 1); \
} while(0)
{
struct point {
GLfloat x;
GLfloat y;
};
/* Create the 7 points (only x,y coords) used to draw a tooth */
struct point p[7] = {
GEAR_POINT (r2, 1), // 0
GEAR_POINT (r2, 2), // 1
GEAR_POINT (r1, 0), // 2
GEAR_POINT (r1, 3), // 3
GEAR_POINT (r0, 0), // 4
GEAR_POINT (r1, 4), // 5
GEAR_POINT (r0, 4), // 6
};
/* Front face */
START_STRIP;
SET_NORMAL (0, 0, 1.0);
v = GEAR_VERT (v, 0, +1);
v = GEAR_VERT (v, 1, +1);
v = GEAR_VERT (v, 2, +1);
v = GEAR_VERT (v, 3, +1);
v = GEAR_VERT (v, 4, +1);
v = GEAR_VERT (v, 5, +1);
v = GEAR_VERT (v, 6, +1);
END_STRIP;
/* Inner face */
START_STRIP;
QUAD_WITH_NORMAL (4, 6);
END_STRIP;
/* Back face */
START_STRIP;
SET_NORMAL (0, 0, -1.0);
v = GEAR_VERT (v, 6, -1);
v = GEAR_VERT (v, 5, -1);
v = GEAR_VERT (v, 4, -1);
v = GEAR_VERT (v, 3, -1);
v = GEAR_VERT (v, 2, -1);
v = GEAR_VERT (v, 1, -1);
v = GEAR_VERT (v, 0, -1);
END_STRIP;
/* Outer face */
START_STRIP;
QUAD_WITH_NORMAL (0, 2);
END_STRIP;
START_STRIP;
QUAD_WITH_NORMAL (1, 0);
END_STRIP;
START_STRIP;
QUAD_WITH_NORMAL (3, 1);
END_STRIP;
START_STRIP;
QUAD_WITH_NORMAL (5, 3);
END_STRIP;
}
}
gear->nvertices = (v - gear->vertices);
/* Store the vertices in a vertex buffer object (VBO) */
glGenBuffers (1, &gear->vbo);
glBindBuffer (GL_ARRAY_BUFFER, gear->vbo);
glBufferData (GL_ARRAY_BUFFER, gear->nvertices * sizeof(GearVertex),
gear->vertices, GL_STATIC_DRAW);
return gear;
}
/**
* Multiplies two 4x4 matrices.
*
* The result is stored in matrix m.
*
* @param m the first matrix to multiply
* @param n the second matrix to multiply
*/
static void
multiply (GLfloat *m, const GLfloat *n)
{
GLfloat tmp[16];
const GLfloat *row, *column;
div_t d;
int i, j;
for (i = 0; i < 16; i++) {
tmp[i] = 0;
d = div(i, 4);
row = n + d.quot * 4;
column = m + d.rem;
for (j = 0; j < 4; j++)
tmp[i] += row[j] * column[j * 4];
}
memcpy (m, &tmp, sizeof tmp);
}
/**
* Rotates a 4x4 matrix.
*
* @param[in,out] m the matrix to rotate
* @param angle the angle to rotate
* @param x the x component of the direction to rotate to
* @param y the y component of the direction to rotate to
* @param z the z component of the direction to rotate to
*/
static void
rotate (GLfloat *m, GLfloat angle, GLfloat x, GLfloat y, GLfloat z)
{
double s, c;
sincos (angle, &s, &c);
{
GLfloat r[16] = {
x * x * (1 - c) + c, y * x * (1 - c) + z * s, x * z * (1 - c) - y * s, 0,
x * y * (1 - c) - z * s, y * y * (1 - c) + c, y * z * (1 - c) + x * s, 0,
x * z * (1 - c) + y * s, y * z * (1 - c) - x * s, z * z * (1 - c) + c, 0,
0, 0, 0, 1
};
multiply (m, r);
}
}
/**
* Translates a 4x4 matrix.
*
* @param[in,out] m the matrix to translate
* @param x the x component of the direction to translate to
* @param y the y component of the direction to translate to
* @param z the z component of the direction to translate to
*/
static void
translate(GLfloat *m, GLfloat x, GLfloat y, GLfloat z)
{
GLfloat t[16] = { 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, x, y, z, 1 };
multiply (m, t);
}
/**
* Creates an identity 4x4 matrix.
*
* @param m the matrix make an identity matrix
*/
static void
identity (GLfloat *m)
{
GLfloat t[16] = {
1.0, 0.0, 0.0, 0.0,
0.0, 1.0, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0,
};
memcpy (m, t, sizeof(t));
}
/**
* Transposes a 4x4 matrix.
*
* @param m the matrix to transpose
*/
static void
transpose (GLfloat *m)
{
GLfloat t[16] = {
m[0], m[4], m[8], m[12],
m[1], m[5], m[9], m[13],
m[2], m[6], m[10], m[14],
m[3], m[7], m[11], m[15]};
memcpy (m, t, sizeof(t));
}
/**
* Inverts a 4x4 matrix.
*
* This function can currently handle only pure translation-rotation matrices.
* Read http://www.gamedev.net/community/forums/topic.asp?topic_id=425118
* for an explanation.
*/
static void
invert (GLfloat *m)
{
GLfloat t[16];
identity (t);
// Extract and invert the translation part 't'. The inverse of a
// translation matrix can be calculated by negating the translation
// coordinates.
t[12] = -m[12]; t[13] = -m[13]; t[14] = -m[14];
// Invert the rotation part 'r'. The inverse of a rotation matrix is
// equal to its transpose.
m[12] = m[13] = m[14] = 0;
transpose (m);
// inv (m) = inv (r) * inv (t)
multiply (m, t);
}
/**
* Calculate a perspective projection transformation.
*
* @param m the matrix to save the transformation in
* @param fovy the field of view in the y direction
* @param aspect the view aspect ratio
* @param zNear the near clipping plane
* @param zFar the far clipping plane
*/
static void
perspective (GLfloat *m, GLfloat fovy, GLfloat aspect, GLfloat zNear, GLfloat zFar)
{
GLfloat tmp[16];
double sine, cosine, cotangent, deltaZ;
GLfloat radians = fovy / 2 * M_PI / 180;
identity (tmp);
deltaZ = zFar - zNear;
sincos (radians, &sine, &cosine);
if ((deltaZ == 0) || (sine == 0) || (aspect == 0))
return;
cotangent = cosine / sine;
tmp[0] = cotangent / aspect;
tmp[5] = cotangent;
tmp[10] = -(zFar + zNear) / deltaZ;
tmp[11] = -1;
tmp[14] = -2 * zNear * zFar / deltaZ;
tmp[15] = 0;
memcpy (m, tmp, sizeof(tmp));
}
/**
* Draws a gear.
*
* @param gear the gear to draw
* @param transform the current transformation matrix
* @param x the x position to draw the gear at
* @param y the y position to draw the gear at
* @param angle the rotation angle of the gear
* @param color the color of the gear
*/
static void
draw_gear (struct gear *gear, GLfloat *transform,
GLfloat x, GLfloat y, GLfloat angle, const GLfloat color[4])
{
GLfloat model_view[16];
GLfloat normal_matrix[16];
GLfloat model_view_projection[16];
int n;
/* Translate and rotate the gear */
memcpy(model_view, transform, sizeof (model_view));
translate(model_view, x, y, 0);
rotate(model_view, 2 * M_PI * angle / 360.0, 0, 0, 1);
/* Create and set the ModelViewProjectionMatrix */
memcpy (model_view_projection,
ProjectionMatrix,
sizeof(model_view_projection));
multiply (model_view_projection, model_view);
glUniformMatrix4fv (ModelViewProjectionMatrix_location, 1, GL_FALSE,
model_view_projection);
/*
* Create and set the NormalMatrix. It's the inverse transpose of the
* ModelView matrix.
*/
memcpy (normal_matrix, model_view, sizeof (normal_matrix));
invert (normal_matrix);
transpose (normal_matrix);
glUniformMatrix4fv (NormalMatrix_location, 1, GL_FALSE, normal_matrix);
/* Set the gear color */
glUniform4fv (MaterialColor_location, 1, color);
/* Set the vertex buffer object to use */
glBindBuffer (GL_ARRAY_BUFFER, gear->vbo);
/* Set up the position of the attributes in the vertex buffer object */
glVertexAttribPointer (0, 3, GL_FLOAT, GL_FALSE,
6 * sizeof(GLfloat), NULL);
glVertexAttribPointer (1, 3, GL_FLOAT, GL_FALSE,
6 * sizeof(GLfloat), (GLfloat *) 0 + 3);
/* Enable the attributes */
glEnableVertexAttribArray (0);
glEnableVertexAttribArray (1);
/* Draw the triangle strips that comprise the gear */
for (n = 0; n < gear->nstrips; n++)
glDrawArrays (GL_TRIANGLE_STRIP,
gear->strips[n].first,
gear->strips[n].count);
/* Disable the attributes */
glDisableVertexAttribArray (1);
glDisableVertexAttribArray (0);
}
/**
* Draws the gears.
*/
static void
gears_draw(void)
{
const static GLfloat red[4] = { 0.8, 0.1, 0.0, 1.0 };
const static GLfloat green[4] = { 0.0, 0.8, 0.2, 1.0 };
const static GLfloat blue[4] = { 0.2, 0.2, 1.0, 1.0 };
GLfloat transform[16];
identity(transform);
glClearColor (0.0, 0.0, 0.0, 0.0);
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
/* Translate and rotate the view */
translate (transform, 0, 0, -20);
rotate (transform, 2 * M_PI * view_rot[0] / 360.0, 1, 0, 0);
rotate (transform, 2 * M_PI * view_rot[1] / 360.0, 0, 1, 0);
rotate (transform, 2 * M_PI * view_rot[2] / 360.0, 0, 0, 1);
/* Draw the gears */
draw_gear (gear1, transform, -3.0, -2.0, angle, red);
draw_gear (gear2, transform, 3.1, -2.0, -2 * angle - 9.0, green);
draw_gear (gear3, transform, -3.1, 4.2, -2 * angle - 25.0, blue);
}
static gboolean
paint_cb (void *user_data)
{
Data *data = user_data;
double elapsed = g_timer_elapsed (data->timer, NULL);
double dt = elapsed - data->last_elapsed;
GError *error = NULL;
/* Draw scene with GLES2 */
if (!cogl_push_gles2_context (data->ctx,
data->gles2_ctx,
data->fb,
data->fb,
&error))
{
g_error ("Failed to push gles2 context: %s\n", error->message);
}
gears_draw ();
cogl_pop_gles2_context (data->ctx);
cogl_onscreen_swap_buffers (COGL_ONSCREEN (data->fb));
/* advance rotation for next frame */
angle += 70.0 * dt; /* 70 degrees per second */
if (angle > 3600.0)
angle -= 3600.0;
data->frames++;
if (elapsed > 5.0) {
GLfloat fps = data->frames / elapsed;
printf ("%d frames in %3.1f seconds = %6.3f FPS\n",
data->frames, elapsed, fps);
g_timer_reset (data->timer);
data->last_elapsed = 0;
data->frames = 0;
}else
data->last_elapsed = elapsed;
/* If the driver can deliver swap complete events then we can remove
* the idle paint callback until we next get a swap complete event
* otherwise we keep the idle paint callback installed and simply
* paint as fast as the driver will allow... */
if (cogl_has_feature (data->ctx, COGL_FEATURE_ID_SWAP_BUFFERS_EVENT))
return FALSE; /* remove the callback */
else
return TRUE;
}
static void
swap_complete_cb (CoglFramebuffer *framebuffer, void *user_data)
{
g_idle_add (paint_cb, user_data);
}
/**
* Handles a new window size or exposure.
*
* @param width the window width
* @param height the window height
*/
static void
gears_reshape (int width, int height)
{
/* Update the projection matrix */
perspective (ProjectionMatrix, 60.0, width / (float)height, 1.0, 1024.0);
/* Set the viewport */
glViewport (0, 0, (GLint) width, (GLint) height);
}
#if 0
/**
* Handles special eglut events.
*
* @param special the event to handle.
*/
static void
gears_special(int special)
{
switch (special) {
case EGLUT_KEY_LEFT:
view_rot[1] += 5.0;
break;
case EGLUT_KEY_RIGHT:
view_rot[1] -= 5.0;
break;
case EGLUT_KEY_UP:
view_rot[0] += 5.0;
break;
case EGLUT_KEY_DOWN:
view_rot[0] -= 5.0;
break;
}
}
#endif
static const char vertex_shader[] =
"attribute vec3 position;\n"
"attribute vec3 normal;\n"
"\n"
"uniform mat4 ModelViewProjectionMatrix;\n"
"uniform mat4 NormalMatrix;\n"
"uniform vec4 LightSourcePosition;\n"
"uniform vec4 MaterialColor;\n"
"\n"
"varying vec4 Color;\n"
"\n"
"void main(void)\n"
"{\n"
" // Transform the normal to eye coordinates\n"
" vec3 N = normalize(vec3(NormalMatrix * vec4(normal, 1.0)));\n"
"\n"
" // The LightSourcePosition is actually its direction for directional light\n"
" vec3 L = normalize(LightSourcePosition.xyz);\n"
"\n"
" // Multiply the diffuse value by the vertex color (which is fixed in this case)\n"
" // to get the actual color that we will use to draw this vertex with\n"
" float diffuse = max(dot(N, L), 0.0);\n"
" Color = diffuse * MaterialColor;\n"
"\n"
" // Transform the position to clip coordinates\n"
" gl_Position = ModelViewProjectionMatrix * vec4(position, 1.0);\n"
"}";
static const char fragment_shader[] =
"precision mediump float;\n"
"varying vec4 Color;\n"
"\n"
"void main(void)\n"
"{\n"
" gl_FragColor = Color;\n"
"}";
static void
gears_init(void)
{
GLuint v, f, program;
const char *p;
char msg[512];
glEnable (GL_CULL_FACE);
glEnable (GL_DEPTH_TEST);
/* Compile the vertex shader */
p = vertex_shader;
v = glCreateShader (GL_VERTEX_SHADER);
glShaderSource (v, 1, &p, NULL);
glCompileShader (v);
glGetShaderInfoLog (v, sizeof msg, NULL, msg);
printf ("vertex shader info: %s\n", msg);
/* Compile the fragment shader */
p = fragment_shader;
f = glCreateShader (GL_FRAGMENT_SHADER);
glShaderSource (f, 1, &p, NULL);
glCompileShader (f);
glGetShaderInfoLog (f, sizeof msg, NULL, msg);
printf ("fragment shader info: %s\n", msg);
/* Create and link the shader program */
program = glCreateProgram ();
glAttachShader (program, v);
glAttachShader (program, f);
glBindAttribLocation (program, 0, "position");
glBindAttribLocation (program, 1, "normal");
glLinkProgram (program);
glGetProgramInfoLog (program, sizeof msg, NULL, msg);
printf ("info: %s\n", msg);
/* Enable the shaders */
glUseProgram (program);
/* Get the locations of the uniforms so we can access them */
ModelViewProjectionMatrix_location =
glGetUniformLocation (program, "ModelViewProjectionMatrix");
NormalMatrix_location =
glGetUniformLocation (program, "NormalMatrix");
LightSourcePosition_location =
glGetUniformLocation (program, "LightSourcePosition");
MaterialColor_location =
glGetUniformLocation (program, "MaterialColor");
/* Set the LightSourcePosition uniform which is constant throughout
* the program */
glUniform4fv (LightSourcePosition_location, 1, LightSourcePosition);
/* make the gears */
gear1 = create_gear (1.0, 4.0, 1.0, 20, 0.7);
gear2 = create_gear (0.5, 2.0, 2.0, 10, 0.7);
gear3 = create_gear (1.3, 2.0, 0.5, 10, 0.7);
}
int
main (int argc, char **argv)
{
Data data;
CoglOnscreen *onscreen;
GError *error = NULL;
GSource *cogl_source;
GMainLoop *loop;
CoglRenderer *renderer;
CoglDisplay *display;
renderer = cogl_renderer_new ();
cogl_renderer_add_constraint (renderer,
COGL_RENDERER_CONSTRAINT_SUPPORTS_COGL_GLES2);
display = cogl_display_new (renderer, NULL);
data.ctx = cogl_context_new (display, NULL);
onscreen = cogl_onscreen_new (data.ctx, 300, 300);
cogl_onscreen_show (onscreen);
data.fb = COGL_FRAMEBUFFER (onscreen);
data.gles2_ctx = cogl_gles2_context_new (data.ctx, &error);
if (!data.gles2_ctx)
g_error ("Failed to create GLES2 context: %s\n", error->message);
/* Draw scene with GLES2 */
if (!cogl_push_gles2_context (data.ctx,
data.gles2_ctx,
data.fb,
data.fb,
&error))
{
g_error ("Failed to push gles2 context: %s\n", error->message);
}
gears_reshape (cogl_framebuffer_get_width (data.fb),
cogl_framebuffer_get_height (data.fb));
/* Initialize the gears */
gears_init();
cogl_pop_gles2_context (data.ctx);
cogl_source = cogl_glib_source_new (data.ctx, G_PRIORITY_DEFAULT);
g_source_attach (cogl_source, NULL);
if (cogl_has_feature (data.ctx, COGL_FEATURE_ID_SWAP_BUFFERS_EVENT))
cogl_onscreen_add_swap_buffers_callback (COGL_ONSCREEN (data.fb),
swap_complete_cb, &data);
g_idle_add (paint_cb, &data);
data.timer = g_timer_new ();
data.frames = 0;
data.last_elapsed = 0;
loop = g_main_loop_new (NULL, TRUE);
g_main_loop_run (loop);
return 0;
}