text: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  #ifndef _GUAC_PROTOCOL_H
  #define _GUAC_PROTOCOL_H
  
  /**
   * Provides functions and structures required for communicating using the
   * Guacamole protocol over a guac_socket connection, such as that provided by
   * guac_client objects.
   *
   * @file protocol.h
   */
  
  #include "layer-types.h"
  #include "object-types.h"
  #include "protocol-types.h"
  #include "socket-types.h"
  #include "stream-types.h"
  #include "timestamp-types.h"
  
  #include <cairo/cairo.h>
  #include <stdarg.h>
  
  /* CONTROL INSTRUCTIONS */
  
  /**
   * Sends an ack instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param stream The guac_stream associated with the operation this ack is
   *               acknowledging.
   * @param error The human-readable description associated with the error or
   *              status update.
   * @param status The status code related to the error or status.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_ack(guac_socket* socket, guac_stream* stream,
          const char* error, guac_protocol_status status);
  
  /**
   * Sends an args instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param args The NULL-terminated array of argument names (strings).
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_args(guac_socket* socket, const char** args);
  
  /**
   * Sends a connect instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param args The NULL-terminated array of argument values (strings).
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_connect(guac_socket* socket, const char** args);
  
  /**
   * Sends a disconnect instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_disconnect(guac_socket* socket);
  
  /**
   * Sends an error instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param error The human-readable description associated with the error.
   * @param status The status code related to the error.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_error(guac_socket* socket, const char* error,
          guac_protocol_status status);
  
  /**
   * Sends a key instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use.
   *
   * @param keysym
   *     The X11 keysym of the key that was pressed or released.
   *
   * @param pressed
   *     Non-zero if the key represented by the given keysym is currently
   *     pressed, zero if it is released.
   *
   * @param timestamp
   *     The server timestamp (in milliseconds) at the point in time this key
   *     event was acknowledged.
   *
   * @return
   *     Zero on success, non-zero on error.
   */
  int guac_protocol_send_key(guac_socket* socket, int keysym, int pressed,
          guac_timestamp timestamp);
  
  /**
   * Sends a log instruction over the given guac_socket connection. This is
   * mainly useful in debugging.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param format A printf-style format string to log.
   * @param ... Arguments to use when filling the format string for printing.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_log(guac_socket* socket, const char* format, ...);
  
  /**
   * Sends a log instruction over the given guac_socket connection. This is
   * mainly useful in debugging.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use.
   *
   * @param format
   *     A printf-style format string to log.
   *
   * @param args
   *     The va_list containing the arguments to be used when filling the
   *     format string for printing.
   *
   * @return
   *     Zero if the instruction was sent successfully, non-zero if an error
   *     occurs.
   */
  int vguac_protocol_send_log(guac_socket* socket, const char* format,
          va_list args);
  
  /**
   * Sends a mouse instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use.
   *
   * @param x
   *     The X coordinate of the current mouse position.
   *
   * @param y
   *     The Y coordinate of the current mouse position.
   *
   * @param button_mask
   *     An integer value representing the current state of each button, where
   *     the Nth bit within the integer is set to 1 if and only if the Nth mouse
   *     button is currently pressed. The lowest-order bit is the left mouse
   *     button, followed by the middle button, right button, and finally the up
   *     and down buttons of the scroll wheel.
   *
   *     @see GUAC_CLIENT_MOUSE_LEFT
   *     @see GUAC_CLIENT_MOUSE_MIDDLE
   *     @see GUAC_CLIENT_MOUSE_RIGHT
   *     @see GUAC_CLIENT_MOUSE_SCROLL_UP
   *     @see GUAC_CLIENT_MOUSE_SCROLL_DOWN
   *
   * @param timestamp
   *     The server timestamp (in milliseconds) at the point in time this mouse
   *     position was acknowledged.
   *
   * @return
   *     Zero on success, non-zero on error.
   */
  int guac_protocol_send_mouse(guac_socket* socket, int x, int y,
          int button_mask, guac_timestamp timestamp);
  
  /**
   * Sends a nest instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @deprecated
   *     The "nest" instruction and the corresponding guac_socket
   *     implementation are no longer necessary, having been replaced by
   *     the streaming instructions ("blob", "ack", "end"). Code using nested
   *     sockets or the "nest" instruction should instead write to a normal
   *     socket directly.
   *
   * @param socket The guac_socket connection to use.
   * @param index The integer index of the stram to send the protocol
   *              data over.
   * @param data A string containing protocol data, which must be UTF-8
   *             encoded and null-terminated.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_nest(guac_socket* socket, int index,
          const char* data);
  
  /**
   * Sends a nop instruction (null-operation) over the given guac_socket
   * connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_nop(guac_socket* socket);
  
  /**
   * Sends a ready instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param id The connection ID of the connection that is ready.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_ready(guac_socket* socket, const char* id);
  
  /**
   * Sends a set instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to set the parameter of.
   * @param name The name of the parameter to set.
   * @param value The value to set the parameter to.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_set(guac_socket* socket, const guac_layer* layer,
          const char* name, const char* value);
  
  /**
   * Sends a select instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param protocol The protocol to request.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_select(guac_socket* socket, const char* protocol);
  
  /**
   * Sends a sync instruction over the given guac_socket connection. The
   * current time in milliseconds should be passed in as the timestamp.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param timestamp The current timestamp (in milliseconds).
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_sync(guac_socket* socket, guac_timestamp timestamp);
  
  /* OBJECT INSTRUCTIONS */
  
  /**
   * Sends a body instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use.
   *
   * @param object
   *     The object to associated with the stream being used.
   *
   * @param stream
   *     The stream to use.
   *
   * @param mimetype
   *     The mimetype of the data being sent.
   *
   * @param name
   *     The name of the stream whose body is being sent, as requested by a "get"
   *     instruction.
   *
   * @return
   *     Zero on success, non-zero on error.
   */
  int guac_protocol_send_body(guac_socket* socket, const guac_object* object,
          const guac_stream* stream, const char* mimetype, const char* name);
  
  /**
   * Sends a filesystem instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use.
   *
   * @param object
   *     The object representing the filesystem being exposed.
   *
   * @param name
   *     A name describing the filesystem being exposed.
   *
   * @return
   *     Zero on success, non-zero on error.
   */
  int guac_protocol_send_filesystem(guac_socket* socket,
          const guac_object* object, const char* name);
  
  /**
   * Sends an undefine instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use.
   *
   * @param object
   *     The object being undefined.
   *
   * @return
   *     Zero on success, non-zero on error.
   */
  int guac_protocol_send_undefine(guac_socket* socket,
          const guac_object* object);
  
  /* MEDIA INSTRUCTIONS */
  
  /**
   * Sends an audio instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use when sending the audio instruction.
   *
   * @param stream
   *     The stream to use for future audio data.
   *
   * @param mimetype
   *     The mimetype of the audio data which will be sent over the given stream.
   *
   * @return
   *     Zero on success, non-zero on error.
   */
  int guac_protocol_send_audio(guac_socket* socket, const guac_stream* stream,
          const char* mimetype);
  
  /**
   * Sends a file instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param stream The stream to use.
   * @param mimetype The mimetype of the data being sent.
   * @param name A name describing the file being sent.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_file(guac_socket* socket, const guac_stream* stream,
          const char* mimetype, const char* name);
  
  /**
   * Sends a pipe instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param stream The stream to use.
   * @param mimetype The mimetype of the data being sent.
   * @param name An arbitrary name uniquely identifying this pipe.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_pipe(guac_socket* socket, const guac_stream* stream,
          const char* mimetype, const char* name);
  
  /**
   * Writes a block of data to the currently in-progress blob which was already
   * created.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param stream The stream to use.
   * @param data The file data to write.
   * @param count The number of bytes within the given buffer of file data
   *              that must be written.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_blob(guac_socket* socket, const guac_stream* stream,
          const void* data, int count);
  
  /**
   * Sends an end instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param stream The stream to use.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_end(guac_socket* socket, const guac_stream* stream);
  
  /**
   * Sends a video instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use when sending the video instruction.
   *
   * @param stream
   *     The stream to use for future video data.
   *
   * @param layer
   *     The destination layer on which the streamed video should be played.
   *
   * @param mimetype
   *     The mimetype of the video data which will be sent over the given stream.
   *
   * @return
   *     Zero on success, non-zero on error.
   */
  int guac_protocol_send_video(guac_socket* socket, const guac_stream* stream,
          const guac_layer* layer, const char* mimetype);
  
  /* DRAWING INSTRUCTIONS */
  
  /**
   * Sends an arc instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The destination layer.
   * @param x The X coordinate of the center of the circle containing the arc.
   * @param y The Y coordinate of the center of the circle containing the arc. 
   * @param radius The radius of the circle containing the arc.
   * @param startAngle The starting angle, in radians.
   * @param endAngle The ending angle, in radians.
   * @param negative Zero if the arc should be drawn in order of increasing
   *                 angle, non-zero otherwise.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_arc(guac_socket* socket, const guac_layer* layer,
          int x, int y, int radius, double startAngle, double endAngle,
          int negative);
  
  /**
   * Sends a cfill instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param mode The composite mode to use.
   * @param layer The destination layer.
   * @param r The red component of the color of the rectangle.
   * @param g The green component of the color of the rectangle.
   * @param b The blue component of the color of the rectangle.
   * @param a The alpha (transparency) component of the color of the rectangle.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_cfill(guac_socket* socket,
          guac_composite_mode mode, const guac_layer* layer,
          int r, int g, int b, int a);
  
  /**
   * Sends a clip instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to set the clipping region of.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_clip(guac_socket* socket, const guac_layer* layer);
  
  /**
   * Sends a close instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The destination layer.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_close(guac_socket* socket, const guac_layer* layer);
  
  /**
   * Sends a copy instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param srcl The source layer.
   * @param srcx The X coordinate of the source rectangle.
   * @param srcy The Y coordinate of the source rectangle.
   * @param w The width of the source rectangle.
   * @param h The height of the source rectangle.
   * @param mode The composite mode to use.
   * @param dstl The destination layer.
   * @param dstx The X coordinate of the destination, where the source rectangle
   *             should be copied.
   * @param dsty The Y coordinate of the destination, where the source rectangle
   *             should be copied.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_copy(guac_socket* socket, 
          const guac_layer* srcl, int srcx, int srcy, int w, int h,
          guac_composite_mode mode, const guac_layer* dstl, int dstx, int dsty);
  
  /**
   * Sends a cstroke instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param mode The composite mode to use.
   * @param layer The destination layer.
   * @param cap The style of line cap to use when drawing the stroke.
   * @param join The style of line join to use when drawing the stroke.
   * @param thickness The thickness of the stroke in pixels.
   * @param r The red component of the color of the rectangle.
   * @param g The green component of the color of the rectangle.
   * @param b The blue component of the color of the rectangle.
   * @param a The alpha (transparency) component of the color of the rectangle.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_cstroke(guac_socket* socket,
          guac_composite_mode mode, const guac_layer* layer,
          guac_line_cap_style cap, guac_line_join_style join, int thickness,
          int r, int g, int b, int a);
  
  /**
   * Sends a cursor instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param x The X coordinate of the cursor hotspot.
   * @param y The Y coordinate of the cursor hotspot.
   * @param srcl The source layer.
   * @param srcx The X coordinate of the source rectangle.
   * @param srcy The Y coordinate of the source rectangle.
   * @param w The width of the source rectangle.
   * @param h The height of the source rectangle.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_cursor(guac_socket* socket, int x, int y,
          const guac_layer* srcl, int srcx, int srcy, int w, int h);
  
  /**
   * Sends a curve instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The destination layer.
   * @param cp1x The X coordinate of the first control point.
   * @param cp1y The Y coordinate of the first control point.
   * @param cp2x The X coordinate of the second control point.
   * @param cp2y The Y coordinate of the second control point.
   * @param x The X coordinate of the endpoint of the curve.
   * @param y The Y coordinate of the endpoint of the curve.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_curve(guac_socket* socket, const guac_layer* layer,
          int cp1x, int cp1y, int cp2x, int cp2y, int x, int y);
  
  /**
   * Sends an identity instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The destination layer.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_identity(guac_socket* socket, const guac_layer* layer);
  
  /**
   * Sends an lfill instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param mode The composite mode to use.
   * @param layer The destination layer.
   * @param srcl The source layer.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_lfill(guac_socket* socket,
          guac_composite_mode mode, const guac_layer* layer,
          const guac_layer* srcl);
  
  /**
   * Sends a line instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The destination layer.
   * @param x The X coordinate of the endpoint of the line.
   * @param y The Y coordinate of the endpoint of the line.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_line(guac_socket* socket, const guac_layer* layer,
          int x, int y);
  
  /**
   * Sends an lstroke instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param mode The composite mode to use.
   * @param layer The destination layer.
   * @param cap The style of line cap to use when drawing the stroke.
   * @param join The style of line join to use when drawing the stroke.
   * @param thickness The thickness of the stroke in pixels.
   * @param srcl The source layer.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_lstroke(guac_socket* socket,
          guac_composite_mode mode, const guac_layer* layer,
          guac_line_cap_style cap, guac_line_join_style join, int thickness,
          const guac_layer* srcl);
  
  /**
   * Sends an img instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket
   *     The guac_socket connection to use when sending the img instruction.
   *
   * @param stream
   *     The stream over which the image data will be sent.
   *
   * @param mode
   *     The composite mode to use when drawing the image over the destination
   *     layer.
   *
   * @param layer
   *     The destination layer.
   *
   * @param mimetype
   *     The mimetype of the image data being sent.
   *
   * @param x
   *     The X coordinate of the upper-left corner of the destination rectangle
   *     within the destination layer, in pixels.
   *
   * @param y
   *     The Y coordinate of the upper-left corner of the destination rectangle
   *     within the destination layer, in pixels.
   *
   * @return
   *     Zero if the instruction was successfully sent, non-zero on error.
   */
  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);
  
  /**
   * Sends a pop instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to set the clipping region of.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_pop(guac_socket* socket, const guac_layer* layer);
  
  /**
   * Sends a push instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to set the clipping region of.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_push(guac_socket* socket, const guac_layer* layer);
  
  /**
   * Sends a rect instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The destination layer.
   * @param x The X coordinate of the rectangle.
   * @param y The Y coordinate of the rectangle.
   * @param width The width of the rectangle.
   * @param height The height of the rectangle.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_rect(guac_socket* socket, const guac_layer* layer,
          int x, int y, int width, int height);
  
  /**
   * Sends a reset instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to set the clipping region of.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_reset(guac_socket* socket, const guac_layer* layer);
  
  /**
   * Sends a start instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The destination layer.
   * @param x The X coordinate of the first point of the subpath.
   * @param y The Y coordinate of the first point of the subpath.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_start(guac_socket* socket, const guac_layer* layer,
          int x, int y);
  
  /**
   * Sends a transfer instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param srcl The source layer.
   * @param srcx The X coordinate of the source rectangle.
   * @param srcy The Y coordinate of the source rectangle.
   * @param w The width of the source rectangle.
   * @param h The height of the source rectangle.
   * @param fn The transfer function to use.
   * @param dstl The destination layer.
   * @param dstx The X coordinate of the destination, where the source rectangle
   *             should be copied.
   * @param dsty The Y coordinate of the destination, where the source rectangle
   *             should be copied.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_transfer(guac_socket* socket, 
          const guac_layer* srcl, int srcx, int srcy, int w, int h,
          guac_transfer_function fn, const guac_layer* dstl, int dstx, int dsty);
  
  /**
   * Sends a transform instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to apply the given transform matrix to.
   * @param a The first value of the affine transform matrix.
   * @param b The second value of the affine transform matrix.
   * @param c The third value of the affine transform matrix.
   * @param d The fourth value of the affine transform matrix.
   * @param e The fifth value of the affine transform matrix.
   * @param f The sixth value of the affine transform matrix.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_transform(guac_socket* socket, 
          const guac_layer* layer,
          double a, double b, double c,
          double d, double e, double f);
  
  /* LAYER INSTRUCTIONS */
  
  /**
   * Sends a dispose instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to dispose.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_dispose(guac_socket* socket, const guac_layer* layer);
  
  /**
   * Sends a distort instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to distort with the given transform matrix.
   * @param a The first value of the affine transform matrix.
   * @param b The second value of the affine transform matrix.
   * @param c The third value of the affine transform matrix.
   * @param d The fourth value of the affine transform matrix.
   * @param e The fifth value of the affine transform matrix.
   * @param f The sixth value of the affine transform matrix.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_distort(guac_socket* socket, 
          const guac_layer* layer,
          double a, double b, double c,
          double d, double e, double f);
  
  /**
   * Sends a move instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to move.
   * @param parent The parent layer the specified layer will be positioned
   *               relative to.
   * @param x The X coordinate of the layer.
   * @param y The Y coordinate of the layer.
   * @param z The Z index of the layer, relative to other layers in its parent.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_move(guac_socket* socket, const guac_layer* layer,
          const guac_layer* parent, int x, int y, int z);
  
  /**
   * Sends a shade instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to shade.
   * @param a The alpha value of the layer.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_shade(guac_socket* socket, const guac_layer* layer,
          int a);
  
  /**
   * Sends a size instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param layer The layer to resize.
   * @param w The new width of the layer.
   * @param h The new height of the layer.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_size(guac_socket* socket, const guac_layer* layer,
          int w, int h);
  
  /* TEXT INSTRUCTIONS */
  
  /**
   * Sends a clipboard instruction over the given guac_socket connection.
   *
   * If an error occurs sending the instruction, a non-zero value is
   * returned, and guac_error is set appropriately.
   *
   * @param socket The guac_socket connection to use.
   * @param stream The stream to use.
   * @param mimetype The mimetype of the clipboard data being sent.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_clipboard(guac_socket* socket, const guac_stream* stream,
          const char* mimetype);
  
  /**
   * Sends a name instruction over the given guac_socket connection.
   *
   * @param socket The guac_socket connection to use.
   * @param name The name to send within the name instruction.
   * @return Zero on success, non-zero on error.
   */
  int guac_protocol_send_name(guac_socket* socket, const char* name);
  
  /**
   * Decodes the given base64-encoded string in-place. The base64 string must
   * be NULL-terminated.
   *
   * @param base64 The base64-encoded string to decode.
   * @return The number of bytes resulting from the decode operation.
   */
  int guac_protocol_decode_base64(char* base64);
  
  #endif
  
  