cairo-path.c

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

cairo_status_t
_cairo_path_fixed_close_path (cairo_path_fixed_t *path)
{
    cairo_status_t status;

    if (! path->has_current_point)
	return CAIRO_STATUS_SUCCESS;

    status = _cairo_path_fixed_add (path, CAIRO_PATH_OP_CLOSE_PATH, NULL, 0);
    if (status)
	return status;

    path->current_point.x = path->last_move_point.x;
    path->current_point.y = path->last_move_point.y;
    path->has_current_point = TRUE;

    return CAIRO_STATUS_SUCCESS;
}

cairo_status_t
_cairo_path_fixed_get_current_point (cairo_path_fixed_t *path,
				     cairo_fixed_t	*x,
				     cairo_fixed_t	*y)
{
    if (! path->has_current_point)
	return CAIRO_STATUS_NO_CURRENT_POINT;

    *x = path->current_point.x;
    *y = path->current_point.y;

    return CAIRO_STATUS_SUCCESS;
}

static cairo_status_t
_cairo_path_fixed_add (cairo_path_fixed_t *path,
		       cairo_path_op_t	   op,
		       cairo_point_t	  *points,
		       int		   num_points)
{
    if (path->op_buf_tail == NULL ||
	path->op_buf_tail->num_ops + 1 > CAIRO_PATH_BUF_SIZE)
    {
	cairo_path_op_buf_t *op_buf;

	op_buf = _cairo_path_op_buf_create ();
	if (op_buf == NULL)
	    return CAIRO_STATUS_NO_MEMORY;

	_cairo_path_fixed_add_op_buf (path, op_buf);
    }

    _cairo_path_op_buf_add_op (path->op_buf_tail, op);

    if (path->arg_buf_tail == NULL ||
	path->arg_buf_tail->num_points + num_points > CAIRO_PATH_BUF_SIZE)
    {
	cairo_path_arg_buf_t *arg_buf;

	arg_buf = _cairo_path_arg_buf_create ();

	if (arg_buf == NULL)
	    return CAIRO_STATUS_NO_MEMORY;

	_cairo_path_fixed_add_arg_buf (path, arg_buf);
    }

    _cairo_path_arg_buf_add_points (path->arg_buf_tail, points, num_points);

    return CAIRO_STATUS_SUCCESS;
}

static void
_cairo_path_fixed_add_op_buf (cairo_path_fixed_t  *path,
			      cairo_path_op_buf_t *op_buf)
{
    op_buf->next = NULL;
    op_buf->prev = path->op_buf_tail;

    if (path->op_buf_tail) {
	path->op_buf_tail->next = op_buf;
    } else {
	path->op_buf_head = op_buf;
    }

    path->op_buf_tail = op_buf;
}

static void
_cairo_path_fixed_add_arg_buf (cairo_path_fixed_t   *path,
			       cairo_path_arg_buf_t *arg_buf)
{
    arg_buf->next = NULL;
    arg_buf->prev = path->arg_buf_tail;

    if (path->arg_buf_tail) {
	path->arg_buf_tail->next = arg_buf;
    } else {
	path->arg_buf_head = arg_buf;
    }

    path->arg_buf_tail = arg_buf;
}

static cairo_path_op_buf_t *
_cairo_path_op_buf_create (void)
{
    cairo_path_op_buf_t *op_buf;

    op_buf = malloc (sizeof (cairo_path_op_buf_t));

    if (op_buf) {
	op_buf->num_ops = 0;
	op_buf->next = NULL;
    }

    return op_buf;
}

static void
_cairo_path_op_buf_destroy (cairo_path_op_buf_t *op_buf)
{
    free (op_buf);
}

static void
_cairo_path_op_buf_add_op (cairo_path_op_buf_t *op_buf,
			   cairo_path_op_t	op)
{
    op_buf->op[op_buf->num_ops++] = op;
}

static cairo_path_arg_buf_t *
_cairo_path_arg_buf_create (void)
{
    cairo_path_arg_buf_t *arg_buf;

    arg_buf = malloc (sizeof (cairo_path_arg_buf_t));

    if (arg_buf) {
	arg_buf->num_points = 0;
	arg_buf->next = NULL;
    }

    return arg_buf;
}

static void
_cairo_path_arg_buf_destroy (cairo_path_arg_buf_t *arg_buf)
{
    free (arg_buf);
}

static void
_cairo_path_arg_buf_add_points (cairo_path_arg_buf_t *arg_buf,
				cairo_point_t	     *points,
				int		      num_points)
{
    int i;

    for (i=0; i < num_points; i++) {
	arg_buf->points[arg_buf->num_points++] = points[i];
    }
}

#define CAIRO_PATH_OP_MAX_ARGS 3

static int const num_args[] =
{
    1, /* cairo_path_move_to */
    1, /* cairo_path_op_line_to */
    3, /* cairo_path_op_curve_to */
    0, /* cairo_path_op_close_path */
};

cairo_status_t
_cairo_path_fixed_interpret (cairo_path_fixed_t			*path,
			     cairo_direction_t			 dir,
			     cairo_path_fixed_move_to_func_t	*move_to,
			     cairo_path_fixed_line_to_func_t	*line_to,
			     cairo_path_fixed_curve_to_func_t	*curve_to,
			     cairo_path_fixed_close_path_func_t	*close_path,
			     void				*closure)
{
    cairo_status_t status;
    int i, arg;
    cairo_path_op_buf_t *op_buf;
    cairo_path_op_t op;
    cairo_path_arg_buf_t *arg_buf = path->arg_buf_head;
    int buf_i = 0;
    cairo_point_t point[CAIRO_PATH_OP_MAX_ARGS];
    cairo_bool_t forward = (dir == CAIRO_DIRECTION_FORWARD);
    int step = forward ? 1 : -1;

    for (op_buf = forward ? path->op_buf_head : path->op_buf_tail;
	 op_buf;
	 op_buf = forward ? op_buf->next : op_buf->prev)
    {
	int start, stop;
	if (forward) {
	    start = 0;
	    stop = op_buf->num_ops;
	} else {
	    start = op_buf->num_ops - 1;
	    stop = -1;
	}

	for (i=start; i != stop; i += step) {
	    op = op_buf->op[i];

	    if (! forward) {
		if (buf_i == 0) {
		    arg_buf = arg_buf->prev;
		    buf_i = arg_buf->num_points;
		}
		buf_i -= num_args[op];
	    }

	    for (arg = 0; arg < num_args[op]; arg++) {
		point[arg] = arg_buf->points[buf_i];
		buf_i++;
		if (buf_i >= arg_buf->num_points) {
		    arg_buf = arg_buf->next;
		    buf_i = 0;
		}
	    }

	    if (! forward) {
		buf_i -= num_args[op];
	    }

	    switch (op) {
	    case CAIRO_PATH_OP_MOVE_TO:
		status = (*move_to) (closure, &point[0]);
		break;
	    case CAIRO_PATH_OP_LINE_TO:
		status = (*line_to) (closure, &point[0]);
		break;
	    case CAIRO_PATH_OP_CURVE_TO:
		status = (*curve_to) (closure, &point[0], &point[1], &point[2]);
		break;
	    case CAIRO_PATH_OP_CLOSE_PATH:
	    default:
		status = (*close_path) (closure);
		break;
	    }
	    if (status)
		return status;
	}
    }

    return CAIRO_STATUS_SUCCESS;
}

static void
_cairo_path_fixed_offset_and_scale (cairo_path_fixed_t *path,
				    cairo_fixed_t offx,
				    cairo_fixed_t offy,
				    cairo_fixed_t scalex,
				    cairo_fixed_t scaley)
{
    cairo_path_arg_buf_t *arg_buf = path->arg_buf_head;
    int i;
    cairo_int64_t i64temp;
    cairo_fixed_t fixedtemp;

    while (arg_buf) {
	 for (i = 0; i < arg_buf->num_points; i++) {
	     if (scalex == CAIRO_FIXED_ONE) {
		 arg_buf->points[i].x += offx;
	     } else {
		 fixedtemp = arg_buf->points[i].x + offx;
		 i64temp = _cairo_int32x32_64_mul (fixedtemp, scalex);
		 arg_buf->points[i].x = _cairo_int64_to_int32(_cairo_int64_rsl (i64temp, 16));
	     }

	     if (scaley == CAIRO_FIXED_ONE) {
		 arg_buf->points[i].y += offy;
	     } else {
		 fixedtemp = arg_buf->points[i].y + offy;
		 i64temp = _cairo_int32x32_64_mul (fixedtemp, scaley);
		 arg_buf->points[i].y = _cairo_int64_to_int32(_cairo_int64_rsl (i64temp, 16));
	     }
	 }

	 arg_buf = arg_buf->next;
    }
}


/**
 * _cairo_path_fixed_device_transform:
 * @path: a #cairo_path_fixed_t to be transformed
 * @device_transform: a matrix with only scaling/translation (no rotation or shear)
 *
 * Transform the fixed-point path according to the scaling and
 * translation of the given matrix. This function assert()s that the
 * given matrix has no rotation or shear elements, (that is, xy and yx
 * are 0.0).
 **/
void
_cairo_path_fixed_device_transform (cairo_path_fixed_t	*path,
				    cairo_matrix_t	*device_transform)
{
    assert (device_transform->yx == 0.0 && device_transform->xy == 0.0);
    /* XXX: FRAGILE: I'm not really sure whether we're doing the
     * "right" thing here if there is both scaling and translation in
     * the matrix. But for now, the internals guarantee that we won't
     * really ever have both going on. */
    _cairo_path_fixed_offset_and_scale (path,
					_cairo_fixed_from_double (device_transform->x0),
					_cairo_fixed_from_double (device_transform->y0),
					_cairo_fixed_from_double (device_transform->xx),
					_cairo_fixed_from_double (device_transform->yy));
}