in src/libguac/protocol.c [961:986]
int guac_protocol_send_img(guac_socket* socket, const guac_stream* stream,
guac_composite_mode mode, const guac_layer* layer,
const char* mimetype, int x, int y) {
int ret_val;
guac_socket_instruction_begin(socket);
ret_val =
guac_socket_write_string(socket, "3.img,")
|| __guac_socket_write_length_int(socket, stream->index)
|| guac_socket_write_string(socket, ",")
|| __guac_socket_write_length_int(socket, mode)
|| guac_socket_write_string(socket, ",")
|| __guac_socket_write_length_int(socket, layer->index)
|| guac_socket_write_string(socket, ",")
|| __guac_socket_write_length_string(socket, mimetype)
|| guac_socket_write_string(socket, ",")
|| __guac_socket_write_length_int(socket, x)
|| guac_socket_write_string(socket, ",")
|| __guac_socket_write_length_int(socket, y)
|| guac_socket_write_string(socket, ";");
guac_socket_instruction_end(socket);
return ret_val;
}