guacamole-spice-protocol/libguac/include/protocol.h

/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is libguac.
 *
 * The Initial Developer of the Original Code is
 * Michael Jumper.
 * Portions created by the Initial Developer are Copyright (C) 2010
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *
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 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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#ifndef _GUAC_PROTOCOL_H
#define _GUAC_PROTOCOL_H

#include <cairo/cairo.h>

#include "layer.h"
#include "socket.h"
#include "timestamp.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
 */

/**
 * Composite modes used by Guacamole draw instructions. Each
 * composite mode maps to a unique channel mask integer.
 */
typedef enum guac_composite_mode {

    /*
     * A: Source where destination transparent = S n D'
     * B: Source where destination opaque      = S n D
     * C: Destination where source transparent = D n S'
     * D: Destination where source opaque      = D n S
     *
     * 0 = Active, 1 = Inactive
     */
                           /* ABCD */
    GUAC_COMP_ROUT  = 0x2, /* 0010 - Clears destination where source opaque  */
    GUAC_COMP_ATOP  = 0x6, /* 0110 - Fill where destination opaque only      */
    GUAC_COMP_XOR   = 0xA, /* 1010 - XOR                                     */
    GUAC_COMP_ROVER = 0xB, /* 1011 - Fill where destination transparent only */
    GUAC_COMP_OVER  = 0xE, /* 1110 - Draw normally                           */
    GUAC_COMP_PLUS  = 0xF, /* 1111 - Add                                     */

    /* Unimplemented in client: */
    /* NOT IMPLEMENTED:       0000 - Clear          */
    /* NOT IMPLEMENTED:       0011 - No operation   */
    /* NOT IMPLEMENTED:       0101 - Additive IN    */
    /* NOT IMPLEMENTED:       0111 - Additive ATOP  */
    /* NOT IMPLEMENTED:       1101 - Additive RATOP */

    /* Buggy in webkit browsers, as they keep channel C on in all cases: */
    GUAC_COMP_RIN   = 0x1, /* 0001 */
    GUAC_COMP_IN    = 0x4, /* 0100 */
    GUAC_COMP_OUT   = 0x8, /* 1000 */
    GUAC_COMP_RATOP = 0x9, /* 1001 */
    GUAC_COMP_SRC   = 0xC  /* 1100 */

    /* Bitwise composite operations (binary) */

    /*
     * A: S' & D'
     * B: S' & D
     * C: S  & D'
     * D: S  & D
     *
     * 0 = Active, 1 = Inactive
     */

} guac_composite_mode;


/**
 * Default transfer functions. There is no current facility in the
 * Guacamole protocol to define custom transfer functions.
 */
typedef enum guac_transfer_function {

    /* Constant functions */               /* ABCD */
    GUAC_TRANSFER_BINARY_BLACK      = 0x0, /* 0000 */
    GUAC_TRANSFER_BINARY_WHITE      = 0xF, /* 1111 */

    /* Copy functions */
    GUAC_TRANSFER_BINARY_SRC        = 0x3, /* 0011 */
    GUAC_TRANSFER_BINARY_DEST       = 0x5, /* 0101 */
    GUAC_TRANSFER_BINARY_NSRC       = 0xC, /* 1100 */
    GUAC_TRANSFER_BINARY_NDEST      = 0xA, /* 1010 */

    /* AND / NAND */
    GUAC_TRANSFER_BINARY_AND        = 0x1, /* 0001 */
    GUAC_TRANSFER_BINARY_NAND       = 0xE, /* 1110 */

    /* OR / NOR */
    GUAC_TRANSFER_BINARY_OR         = 0x7, /* 0111 */
    GUAC_TRANSFER_BINARY_NOR        = 0x8, /* 1000 */

    /* XOR / XNOR */
    GUAC_TRANSFER_BINARY_XOR        = 0x6, /* 0110 */
    GUAC_TRANSFER_BINARY_XNOR       = 0x9, /* 1001 */

    /* AND / NAND with inverted source */
    GUAC_TRANSFER_BINARY_NSRC_AND   = 0x4, /* 0100 */
    GUAC_TRANSFER_BINARY_NSRC_NAND  = 0xB, /* 1011 */

    /* OR / NOR with inverted source */
    GUAC_TRANSFER_BINARY_NSRC_OR    = 0xD, /* 1101 */
    GUAC_TRANSFER_BINARY_NSRC_NOR   = 0x2, /* 0010 */

    /* AND / NAND with inverted destination */
    GUAC_TRANSFER_BINARY_NDEST_AND  = 0x2, /* 0010 */
    GUAC_TRANSFER_BINARY_NDEST_NAND = 0xD, /* 1101 */

    /* OR / NOR with inverted destination */
    GUAC_TRANSFER_BINARY_NDEST_OR   = 0xB, /* 1011 */
    GUAC_TRANSFER_BINARY_NDEST_NOR  = 0x4  /* 0100 */

} guac_transfer_function;

/**
 * Supported line cap styles
 */
typedef enum guac_line_cap_style {
    GUAC_LINE_CAP_BUTT   = 0x0,
    GUAC_LINE_CAP_ROUND  = 0x1,
    GUAC_LINE_CAP_SQUARE = 0x2
} guac_line_cap_style;

/**
 * Supported line join styles
 */
typedef enum guac_line_join_style {
    GUAC_LINE_JOIN_BEVEL = 0x0,
    GUAC_LINE_JOIN_MITER = 0x1,
    GUAC_LINE_JOIN_ROUND = 0x2
} guac_line_join_style;

/* CONTROL INSTRUCTIONS */

/**
 * 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 description associated with the error.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_error(guac_socket* socket, const char* error);

/**
 * 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.
 *
 * @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 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);

/* 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.
 * @param channel The index of the audio channel the sound should play on.
 * @param mimetype The mimetype of the data being sent.
 * @param duration The duration of the sound being sent, in milliseconds.
 * @param data The audio data to be sent.
 * @param size The number of bytes of audio data to send.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_audio(guac_socket* socket, int channel,
        const char* mimetype, double duration, void* data, int size);

/**
 * Begins a audio instruction over the given guac_socket connection. Only the
 * initial non-data part of the instruction and the length of the data part
 * of the instruction are sent. The actual contents of the data must be
 * sent with guac_protocol_send_audio_data(), and the instruction must be
 * completed with guac_protocol_send_audio_end().
 *
 * Note that the size of the audio to be sent MUST be known ahead of time,
 * even though the data of the audio may be sent in chunks.
 *
 * No further instruction data may be sent along the givven guac_socket
 * except via guac_protocol_send_audio_data() until the audio instruction
 * is completed with guac_protocol_send_audio_end().
 *
 * 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 channel The index of the audio channel the sound should play on.
 * @param mimetype The mimetype of the data being sent.
 * @param duration The duration of the audio being sent, in milliseconds.
 * @param size The number of bytes of audio data to send.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_audio_header(guac_socket* socket,
        int channel, const char* mimetype, double duration, int size);

/**
 * Writes a block of audio data to the currently in-progress audio instruction
 * which was started with guac_protocol_send_audio_header(). Exactly the
 * number of requested bytes are written unless an error occurs. This function
 * may be called multiple times per audio instruction for each chunk of audio
 * data being written, allowing the potentially huge audio instruction to be
 * split across multiple writes.
 *
 * 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 data The audio data to write.
 * @param count The number of bytes within the given buffer of audio data
 *              that must be written.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_audio_data(guac_socket* socket, void* data, int count);

/**
 * Completes the audio instruction which was started with
 * guac_protocol_send_audio_header(), and whose data has been written with
 * guac_protocol_send_audio_data().
 *
 * 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_audio_end(guac_socket* socket);

/**
 * 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 name A name describing the file being sent.
 * @param mimetype The mimetype of the data being sent.
 * @param data The file data to be sent.
 * @param size The number of bytes of file data to send.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_file(guac_socket* socket, const char* name,
        const char* mimetype, void* data, int size);

/**
 * Begins a file instruction over the given guac_socket connection. Only the
 * initial non-data part of the instruction and the length of the data part
 * of the instruction are sent. The actual contents of the data must be
 * sent with guac_protocol_send_file_data(), and the instruction must be
 * completed with guac_protocol_send_file_end().
 *
 * Note that the size of the file to be sent MUST be known ahead of time,
 * even though the data of the file may be sent in chunks.
 *
 * No further instruction data may be sent along the givven guac_socket
 * except via guac_protocol_send_file_data() until the file instruction
 * is completed with guac_protocol_send_file_end().
 *
 * 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 name A name describing the file being sent.
 * @param mimetype The mimetype of the data being sent.
 * @param size The number of bytes of file data to send.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_file_header(guac_socket* socket, const char* name,
        const char* mimetype, int size);

/**
 * Writes a block of file data to the currently in-progress file instruction
 * which was started with guac_protocol_send_file_header(). Exactly the
 * number of requested bytes are written unless an error occurs. This function
 * may be called multiple times per file instruction for each chunk of file
 * data being written, allowing the potentially huge file instruction to be
 * split across multiple writes.
 *
 * 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 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_file_data(guac_socket* socket, void* data, int count);

/**
 * Completes the file instruction which was started with
 * guac_protocol_send_file_header(), and whose data has been written with
 * guac_protocol_send_file_data().
 *
 * 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_file_end(guac_socket* socket);

/**
 * 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.
 * @param layer The destination layer.
 * @param mimetype The mimetype of the data being sent.
 * @param duration The duration of the video being sent, in milliseconds.
 * @param data The video data to be sent.
 * @param size The number of bytes of video data to send.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_video(guac_socket* socket, const guac_layer* layer,
        const char* mimetype, double duration, void* data, int size);

/**
 * Begins a video instruction over the given guac_socket connection. Only the
 * initial non-data part of the instruction and the length of the data part
 * of the instruction are sent. The actual contents of the data must be
 * sent with guac_protocol_send_video_data(), and the instruction must be
 * completed with guac_protocol_send_video_end().
 *
 * Note that the size of the video to be sent MUST be known ahead of time,
 * even though the data of the video may be sent in chunks.
 *
 * No further instruction data may be sent along the givven guac_socket
 * except via guac_protocol_send_video_data() until the video instruction
 * is completed with guac_protocol_send_video_end().
 *
 * 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 mimetype The mimetype of the data being sent.
 * @param duration The duration of the video being sent, in milliseconds.
 * @param size The number of bytes of video data to send.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_video_header(guac_socket* socket,
        const guac_layer* layer, const char* mimetype, double duration, int size);

/**
 * Writes a block of video data to the currently in-progress video instruction
 * which was started with guac_protocol_send_video_header(). Exactly the
 * number of requested bytes are written unless an error occurs. This function
 * may be called multiple times per video instruction for each chunk of video
 * data being written, allowing the potentially huge video instruction to be
 * split across multiple writes.
 *
 * 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 data The video data to write.
 * @param count The number of bytes within the given buffer of video data
 *              that must be written.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_video_data(guac_socket* socket, void* data, int count);

/**
 * Completes the video instruction which was started with
 * guac_protocol_send_video_header(), and whose data has been written with
 * guac_protocol_send_video_data().
 *
 * 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_video_end(guac_socket* socket);

/* 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 a png instruction over the given guac_socket connection. The PNG image
 * data given will be automatically base64-encoded for transmission.
 *
 * 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 x The destination X coordinate.
 * @param y The destination Y coordinate.
 * @param surface A cairo surface containing the image data to send.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_png(guac_socket* socket, guac_composite_mode mode,
        const guac_layer* layer, int x, int y, cairo_surface_t* surface);

/**
 * 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 data The clipboard data to send.
 * @return Zero on success, non-zero on error.
 */
int guac_protocol_send_clipboard(guac_socket* socket, const char* data);

/**
 * 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);

#endif