/* example to use pangocairo to render text projected on a path *//* Written by Behdad Esfahbod, 2006.  Not copyrighted, in public domain. */#include <math.h>#include <stdlib.h>#include <pango/pangocairo.h>void fancy_cairo_stroke (cairo_t *cr);void fancy_cairo_stroke_preserve (cairo_t *cr);static doubletwo_points_distance (cairo_path_data_t *a, cairo_path_data_t *b){  double dx, dy;  dx = b->point.x - a->point.x;  dy = b->point.y - a->point.y;  return sqrt (dx * dx + dy * dy);}typedef double parametrization_t;static parametrization_t *parametrize_path (cairo_path_t *path){  int i;  cairo_path_data_t *data, current_point;  parametrization_t *parametrization;  parametrization = malloc (path->num_data * sizeof (parametrization[0]));  for (i=0; i < path->num_data; i += path->data[i].header.length) {    data = &path->data[i];    parametrization[i] = 0.0;    switch (data->header.type) {    case CAIRO_PATH_MOVE_TO:	current_point = data[1];	break;    case CAIRO_PATH_LINE_TO:	parametrization[i] = two_points_distance (&current_point, &data[1]);	current_point = data[1];	break;    case CAIRO_PATH_CURVE_TO:	/*	parametrization[i] = curve_length (current_point.point.x, current_point.point.x,					   data[1].point.x, data[1].point.y,					   data[2].point.x, data[2].point.y,					   data[3].point.x, data[3].point.y);					   */	parametrization[i] = two_points_distance (&current_point, &data[1]);	parametrization[i] += two_points_distance (&data[1], &data[2]);	parametrization[i] += two_points_distance (&data[2], &data[3]);	current_point = data[3];	break;    case CAIRO_PATH_CLOSE_PATH:	break;    }  }  return parametrization;}static void_fancy_cairo_stroke (cairo_t *cr, cairo_bool_t preserve){  int i;  double line_width;  cairo_path_t *path;  cairo_path_data_t *data;  const double dash[] = {10, 10};  cairo_save (cr);  cairo_set_source_rgb (cr, 1.0, 0.0, 0.0);  line_width = cairo_get_line_width (cr);  path = cairo_copy_path (cr);  cairo_new_path (cr);  cairo_save (cr);  cairo_set_line_width (cr, line_width / 3);  cairo_set_dash (cr, dash, G_N_ELEMENTS (dash), 0);  for (i=0; i < path->num_data; i += path->data[i].header.length) {    data = &path->data[i];    switch (data->header.type) {    case CAIRO_PATH_MOVE_TO:    case CAIRO_PATH_LINE_TO:	cairo_move_to (cr, data[1].point.x, data[1].point.y);	break;    case CAIRO_PATH_CURVE_TO:	cairo_line_to (cr, data[1].point.x, data[1].point.y);	cairo_move_to (cr, data[2].point.x, data[2].point.y);	cairo_line_to (cr, data[3].point.x, data[3].point.y);	break;    case CAIRO_PATH_CLOSE_PATH:	break;    }  }  cairo_stroke (cr);  cairo_restore (cr);  cairo_save (cr);  cairo_set_line_width (cr, line_width * 4);  cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);  for (i=0; i < path->num_data; i += path->data[i].header.length) {    data = &path->data[i];    switch (data->header.type) {    case CAIRO_PATH_MOVE_TO:	cairo_move_to (cr, data[1].point.x, data[1].point.y);	break;    case CAIRO_PATH_LINE_TO:	cairo_rel_line_to (cr, 0, 0);	cairo_move_to (cr, data[1].point.x, data[1].point.y);	break;    case CAIRO_PATH_CURVE_TO:	cairo_rel_line_to (cr, 0, 0);	cairo_move_to (cr, data[1].point.x, data[1].point.y);	cairo_rel_line_to (cr, 0, 0);	cairo_move_to (cr, data[2].point.x, data[2].point.y);	cairo_rel_line_to (cr, 0, 0);	cairo_move_to (cr, data[3].point.x, data[3].point.y);	break;    case CAIRO_PATH_CLOSE_PATH:	cairo_rel_line_to (cr, 0, 0);	break;    }  }  cairo_rel_line_to (cr, 0, 0);  cairo_stroke (cr);  cairo_restore (cr);  for (i=0; i < path->num_data; i += path->data[i].header.length) {    data = &path->data[i];    switch (data->header.type) {    case CAIRO_PATH_MOVE_TO:	cairo_move_to (cr, data[1].point.x, data[1].point.y);	break;    case CAIRO_PATH_LINE_TO:	cairo_line_to (cr, data[1].point.x, data[1].point.y);	break;    case CAIRO_PATH_CURVE_TO:	cairo_curve_to (cr, data[1].point.x, data[1].point.y,			    data[2].point.x, data[2].point.y,			    data[3].point.x, data[3].point.y);	break;    case CAIRO_PATH_CLOSE_PATH:	cairo_close_path (cr);	break;    }  }  cairo_stroke (cr);  if (preserve)    cairo_append_path (cr, path);  cairo_path_destroy (path);  cairo_restore (cr);}voidfancy_cairo_stroke (cairo_t *cr){  _fancy_cairo_stroke (cr, FALSE);}voidfancy_cairo_stroke_preserve (cairo_t *cr){  _fancy_cairo_stroke (cr, TRUE);}typedef void (*transform_point_func_t) (void *closure, double *x, double *y);static voidtransform_path (cairo_path_t *path, transform_point_func_t f, void *closure){  int i;  cairo_path_data_t *data;  for (i=0; i < path->num_data; i += path->data[i].header.length) {    data = &path->data[i];    switch (data->header.type) {    case CAIRO_PATH_CURVE_TO:      f (closure, &data[3].point.x, &data[3].point.y);      f (closure, &data[2].point.x, &data[2].point.y);    case CAIRO_PATH_MOVE_TO:    case CAIRO_PATH_LINE_TO:      f (closure, &data[1].point.x, &data[1].point.y);      break;    case CAIRO_PATH_CLOSE_PATH:      break;    }  }}typedef struct {  cairo_path_t *path;  parametrization_t *parametrization;} parametrized_path_t;static voidpoint_on_path (parametrized_path_t *param,	       double *x, double *y){  int i;  double ratio, oldy = *y, d = *x, dx, dy;  cairo_path_data_t *data, current_point;  cairo_path_t *path = param->path;  parametrization_t *parametrization = param->parametrization;  for (i=0; i + path->data[i].header.length < path->num_data &&	    (d > parametrization[i] ||	     path->data[i].header.type == CAIRO_PATH_MOVE_TO);       i += path->data[i].header.length) {    d -= parametrization[i];    data = &path->data[i];    switch (data->header.type) {    case CAIRO_PATH_MOVE_TO:	current_point = data[1];	break;    case CAIRO_PATH_LINE_TO:	current_point = data[1];	break;    case CAIRO_PATH_CURVE_TO:	current_point = data[3];	break;    case CAIRO_PATH_CLOSE_PATH:	break;    }  }  data = &path->data[i];  switch (data->header.type) {  case CAIRO_PATH_MOVE_TO:      break;  case CAIRO_PATH_LINE_TO:      ratio = d / parametrization[i];      *x = current_point.point.x * (1 - ratio) + data[1].point.x * ratio;      *y = current_point.point.y * (1 - ratio) + data[1].point.y * ratio;      dx = -(current_point.point.x - data[1].point.x);      dy = -(current_point.point.y - data[1].point.y);      d = oldy;      ratio = d / parametrization[i];      /*ratio = d / sqrt (dx * dx + dy * dy);*/      *x += -dy * ratio;      *y +=  dx * ratio;      break;  case CAIRO_PATH_CURVE_TO:      ratio = d / parametrization[i];      *x = current_point.point.x * (1 - ratio) * (1 - ratio) * (1 - ratio)	 + 3 *   data[1].point.x * (1 - ratio) * (1 - ratio) * ratio	 + 3 *   data[2].point.x * (1 - ratio) *      ratio  * ratio	 +       data[3].point.x *      ratio  *      ratio  * ratio;      *y = current_point.point.y * (1 - ratio) * (1 - ratio) * (1 - ratio)	 + 3 *   data[1].point.y * (1 - ratio) * (1 - ratio) * ratio	 + 3 *   data[2].point.y * (1 - ratio) *      ratio  * ratio	 +       data[3].point.y *      ratio  *      ratio  * ratio;      dx =-3 * current_point.point.x * (1 - ratio) * (1 - ratio)	 + 3 *       data[1].point.x * (1 - 4 * ratio + 3 * ratio * ratio)	 + 3 *       data[2].point.x * (    2 * ratio - 3 * ratio * ratio)	 + 3 *       data[3].point.x *      ratio  *      ratio;      dy =-3 * current_point.point.y * (1 - ratio) * (1 - ratio)	 + 3 *       data[1].point.y * (1 - 4 * ratio + 3 * ratio * ratio)	 + 3 *       data[2].point.y * (    2 * ratio - 3 * ratio * ratio)	 + 3 *       data[3].point.y *      ratio  *      ratio;      d = oldy;      ratio = d / sqrt (dx * dx + dy * dy);      *x += -dy * ratio;      *y +=  dx * ratio;      break;  case CAIRO_PATH_CLOSE_PATH:      break;  }}static voidmap_path_onto (cairo_t *cr, cairo_path_t *path){  cairo_path_t *current_path;  parametrized_path_t param;  param.path = path;  param.parametrization = parametrize_path (path);  current_path = cairo_copy_path (cr);  cairo_new_path (cr);  transform_path (current_path,		  (transform_point_func_t) point_on_path, &param);  cairo_append_path (cr, current_path);}typedef void (*draw_path_func_t) (cairo_t *cr);static voiddraw_text (cairo_t *cr,	   double x,	   double y,	   const char *font,	   const char *text){  PangoLayout *layout;  PangoLayoutLine *line;  PangoFontDescription *desc;  cairo_font_options_t *font_options;  font_options = cairo_font_options_create ();  cairo_font_options_set_hint_style (font_options, CAIRO_HINT_STYLE_NONE);  cairo_font_options_set_hint_metrics (font_options, CAIRO_HINT_METRICS_OFF);  cairo_set_font_options (cr, font_options);  cairo_font_options_destroy (font_options);  layout = pango_cairo_create_layout (cr);  desc = pango_font_description_from_string (font);  pango_layout_set_font_description (layout, desc);  pango_font_description_free (desc);  pango_layout_set_text (layout, text, -1);  /* Use pango_layout_get_line() instead of pango_layout_get_line_readonly()   * for older versions of pango   */  line = pango_layout_get_line_readonly (layout, 0);  cairo_move_to (cr, x, y);  pango_cairo_layout_line_path (cr, line);  g_object_unref (layout);}static voiddraw_twisted (cairo_t *cr,	      double x,	      double y,	      const char *font,	      const char *text){  cairo_path_t *path;  cairo_save (cr);  /* Decrease tolerance a bit, since it's going to be magnified */  cairo_set_tolerance (cr, 0.05);  path = cairo_copy_path_flat (cr);  /*path = cairo_copy_path (cr);*/  cairo_new_path (cr);  draw_text (cr, x, y, font, text);  map_path_onto (cr, path);  cairo_fill_preserve (cr);  cairo_save (cr);  cairo_set_source_rgb (cr, 0.1, 0.1, 0.1);  cairo_stroke (cr);  cairo_restore (cr);  cairo_restore (cr);}static voiddraw_dream (cairo_t *cr){  cairo_move_to (cr, 50, 650);  cairo_rel_line_to (cr, 250, 50);  cairo_rel_curve_to (cr, 250, 50, 600, -50, 600, -250);  cairo_rel_curve_to (cr, 0, -400, -300, -100, -800, -300);  cairo_set_line_width (cr, 1.5);  cairo_set_source_rgba (cr, 0.3, 0.3, 1.0, 0.3);  fancy_cairo_stroke_preserve (cr);  draw_twisted (cr,		0, 0,		"Serif 72",		"It was a dream... Oh Just a dream...");}static voiddraw_wow (cairo_t *cr){  cairo_move_to (cr, 400, 780);  cairo_rel_curve_to (cr, 50, -50, 150, -50, 200, 0);  cairo_scale (cr, 1.0, 2.0);  cairo_set_line_width (cr, 2.0);  cairo_set_source_rgba (cr, 0.3, 1.0, 0.3, 1.0);  fancy_cairo_stroke_preserve (cr);  draw_twisted (cr,		-20, -150,		"Serif 60",		"WOW!");}int main (int argc, char **argv){  cairo_t *cr;  char *filename;  cairo_status_t status;  cairo_surface_t *surface;  if (argc != 2)    {      g_printerr ("Usage: cairotwisted OUTPUT_FILENAME\n");      return 1;    }  filename = argv[1];  surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,					1000, 800);  cr = cairo_create (surface);  /* cairo_scale (cr, 0.5, 0.5); */  cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);  cairo_paint (cr);  draw_dream (cr);  draw_wow (cr);  cairo_destroy (cr);  status = cairo_surface_write_to_png (surface, filename);  cairo_surface_destroy (surface);  if (status != CAIRO_STATUS_SUCCESS)    {      g_printerr ("Could not save png to '%s'\n", filename);      return 1;    }  return 0;}