module xkbcommon.xkbcommon;

// original copyrights from libxkbcommon
/*
 * Copyright 1985, 1987, 1990, 1998  The Open Group
 * Copyright 2008  Dan Nicholson
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * Except as contained in this notice, the names of the authors or their
 * institutions shall not be used in advertising or otherwise to promote the
 * sale, use or other dealings in this Software without prior written
 * authorization from the authors.
 */

/************************************************************
 * Copyright (c) 1993 by Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of Silicon Graphics not be
 * used in advertising or publicity pertaining to distribution
 * of the software without specific prior written permission.
 * Silicon Graphics makes no representation about the suitability
 * of this software for any purpose. It is provided "as is"
 * without any express or implied warranty.
 *
 * SILICON GRAPHICS DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
 * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON
 * GRAPHICS BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION  WITH
 * THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 ********************************************************/

/*
 * Copyright © 2009-2012 Daniel Stone
 * Copyright © 2012 Intel Corporation
 * Copyright © 2012 Ran Benita
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Author: Daniel Stone <daniel@fooishbar.org>
 */

import core.stdc.stdio : FILE;

extern(C):

/**
 * @file
 * Main libxkbcommon API.
 */

/**
 * @struct xkb_context
 * Opaque top level library context object.
 *
 * The context contains various general library data and state, like
 * logging level and include paths.
 *
 * Objects are created in a specific context, and multiple contexts may
 * coexist simultaneously.  Objects from different contexts are completely
 * separated and do not share any memory or state.
 */
struct xkb_context;

/**
 * @struct xkb_keymap
 * Opaque compiled keymap object.
 *
 * The keymap object holds all of the static keyboard information obtained
 * from compiling XKB files.
 *
 * A keymap is immutable after it is created (besides reference counts, etc.);
 * if you need to change it, you must create a new one.
 */
struct xkb_keymap;

/**
 * @struct xkb_state
 * Opaque keyboard state object.
 *
 * State objects contain the active state of a keyboard (or keyboards), such
 * as the currently effective layout and the active modifiers.  It acts as a
 * simple state machine, wherein key presses and releases are the input, and
 * key symbols (keysyms) are the output.
 */
struct xkb_state;

/**
 * A number used to represent a physical key on a keyboard.
 *
 * A standard PC-compatible keyboard might have 102 keys.  An appropriate
 * keymap would assign each of them a keycode, by which the user should
 * refer to the key throughout the library.
 *
 * Historically, the X11 protocol, and consequentially the XKB protocol,
 * assign only 8 bits for keycodes.  This limits the number of different
 * keys that can be used simultaneously in a single keymap to 256
 * (disregarding other limitations).  This library does not share this limit;
 * keycodes beyond 255 ('extended keycodes') are not treated specially.
 * Keymaps and applications which are compatible with X11 should not use
 * these keycodes.
 *
 * The values of specific keycodes are determined by the keymap and the
 * underlying input system.  For example, with an X11-compatible keymap
 * and Linux evdev scan codes (see linux/input.h), a fixed offset is used:
 *
 * @code
 * xkb_keycode_t keycode_A = KEY_A + 8;
 * @endcode
 *
 * @sa xkb_keycode_is_legal_ext() xkb_keycode_is_legal_x11()
 */
alias xkb_keycode_t = uint;

/**
 * A number used to represent the symbols generated from a key on a keyboard.
 *
 * A key, represented by a keycode, may generate different symbols according
 * to keyboard state.  For example, on a QWERTY keyboard, pressing the key
 * labled \<A\> generates the symbol 'a'.  If the Shift key is held, it
 * generates the symbol 'A'.  If a different layout is used, say Greek,
 * it generates the symbol 'α'.  And so on.
 *
 * Each such symbol is represented by a keysym.  Note that keysyms are
 * somewhat more general, in that they can also represent some "function",
 * such as "Left" or "Right" for the arrow keys.  For more information,
 * see:
 * http://www.x.org/releases/X11R7.7/doc/xproto/x11protocol.html#keysym_encoding
 *
 * Specifically named keysyms can be found in the
 * xkbcommon/xkbcommon-keysyms.h header file.  Their name does not include
 * the XKB_KEY_ prefix.
 *
 * Besides those, any Unicode/ISO 10646 character in the range U0100 to
 * U10FFFF can be represented by a keysym value in the range 0x01000100 to
 * 0x0110FFFF.  The name of Unicode keysyms is "U<codepoint>", e.g. "UA1B2".
 *
 * The name of other unnamed keysyms is the hexadecimal representation of
 * their value, e.g. "0xabcd1234".
 *
 * Keysym names are case-sensitive.
 */
alias xkb_keysym_t = uint;

/**
 * Index of a keyboard layout.
 *
 * The layout index is a state component which detemines which <em>keyboard
 * layout</em> is active.  These may be different alphabets, different key
 * arrangements, etc.
 *
 * Layout indices are consecutive.  The first layout has index 0.
 *
 * Each layout is not required to have a name, and the names are not
 * guaranteed to be unique (though they are usually provided and unique).
 * Therefore, it is not safe to use the name as a unique identifier for a
 * layout.  Layout names are case-sensitive.
 *
 * Layouts are also called "groups" by XKB.
 *
 * @sa xkb_keymap_num_layouts() xkb_keymap_num_layouts_for_key()
 */
alias xkb_layout_index_t = uint;
/** A mask of layout indices. */
alias xkb_layout_mask_t = uint;

/**
 * Index of a shift level.
 *
 * Any key, in any layout, can have several <em>shift levels</em>.  Each
 * shift level can assign different keysyms to the key.  The shift level
 * to use is chosen according to the current keyboard state; for example,
 * if no keys are pressed, the first level may be used; if the Left Shift
 * key is pressed, the second; if Num Lock is pressed, the third; and
 * many such combinations are possible (see xkb_mod_index_t).
 *
 * Level indices are consecutive.  The first level has index 0.
 */
alias xkb_level_index_t = uint;

/**
 * Index of a modifier.
 *
 * A @e modifier is a state component which changes the way keys are
 * interpreted.  A keymap defines a set of modifiers, such as Alt, Shift,
 * Num Lock or Meta, and specifies which keys may @e activate which
 * modifiers (in a many-to-many relationship, i.e. a key can activate
 * several modifiers, and a modifier may be activated by several keys.
 * Different keymaps do this differently).
 *
 * When retrieving the keysyms for a key, the active modifier set is
 * consulted; this detemines the correct shift level to use within the
 * currently active layout (see xkb_level_index_t).
 *
 * Modifier indices are consecutive.  The first modifier has index 0.
 *
 * Each modifier must have a name, and the names are unique.  Therefore, it
 * is safe to use the name as a unique identifier for a modifier.  The names
 * of some common modifiers are provided in the xkbcommon/xkbcommon-names.h
 * header file.  Modifier names are case-sensitive.
 *
 * @sa xkb_keymap_num_mods()
 */
alias xkb_mod_index_t = uint;
/** A mask of modifier indices. */
alias xkb_mod_mask_t = uint;

/**
 * Index of a keyboard LED.
 *
 * LEDs are logical objects which may be @e active or @e inactive.  They
 * typically correspond to the lights on the keyboard. Their state is
 * determined by the current keyboard state.
 *
 * LED indices are non-consecutive.  The first LED has index 0.
 *
 * Each LED must have a name, and the names are unique. Therefore,
 * it is safe to use the name as a unique identifier for a LED.  The names
 * of some common LEDs are provided in the xkbcommon/xkbcommon-names.h
 * header file.  LED names are case-sensitive.
 *
 * @warning A given keymap may specify an exact index for a given LED.
 * Therefore, LED indexing is not necessarily sequential, as opposed to
 * modifiers and layouts.  This means that when iterating over the LEDs
 * in a keymap using e.g. xkb_keymap_num_leds(), some indices might be
 * invalid.  Given such an index, functions like xkb_keymap_led_get_name()
 * will return NULL, and xkb_state_led_index_is_active() will return -1.
 *
 * LEDs are also called "indicators" by XKB.
 *
 * @sa xkb_keymap_num_leds()
 */
alias xkb_led_index_t = uint;
/** A mask of LED indices. */
alias xkb_led_mask_t = uint;

enum XKB_KEYCODE_INVALID = 0xffffffff;
enum XKB_LAYOUT_INVALID  = 0xffffffff;
enum XKB_LEVEL_INVALID   = 0xffffffff;
enum XKB_MOD_INVALID     = 0xffffffff;
enum XKB_LED_INVALID     = 0xffffffff;

enum XKB_KEYCODE_MAX     = 0xffffffff-1;

/**
 * Test whether a value is a valid extended keycode.
 * @sa xkb_keycode_t
 **/
extern(D)
auto xkb_keycode_is_legal_ext(K)(K key) {
    return key <= XKB_KEYCODE_MAX;
}

/**
 * Test whether a value is a valid X11 keycode.
 * @sa xkb_keycode_t
 */
extern(D)
auto xkb_keycode_is_legal_x11(K)(K key) {
    return key >= 8 && key <= 255;
}

/**
 * Names to compile a keymap with, also known as RMLVO.
 *
 * The names are the common configuration values by which a user picks
 * a keymap.
 *
 * If the entire struct is NULL, then each field is taken to be NULL.
 * You should prefer passing NULL instead of choosing your own defaults.
 */
struct xkb_rule_names {
    /**
     * The rules file to use. The rules file describes how to interpret
     * the values of the model, layout, variant and options fields.
     *
     * If NULL or the empty string "", a default value is used.
     * If the XKB_DEFAULT_RULES environment variable is set, it is used
     * as the default.  Otherwise the system default is used.
     */
    const(char) *rules;
    /**
     * The keyboard model by which to interpret keycodes and LEDs.
     *
     * If NULL or the empty string "", a default value is used.
     * If the XKB_DEFAULT_MODEL environment variable is set, it is used
     * as the default.  Otherwise the system default is used.
     */
    const(char) *model;
    /**
     * A comma separated list of layouts (languages) to include in the
     * keymap.
     *
     * If NULL or the empty string "", a default value is used.
     * If the XKB_DEFAULT_LAYOUT environment variable is set, it is used
     * as the default.  Otherwise the system default is used.
     */
    const(char) *layout;
    /**
     * A comma separated list of variants, one per layout, which may
     * modify or augment the respective layout in various ways.
     *
     * If NULL or the empty string "", and a default value is also used
     * for the layout, a default value is used.  Otherwise no variant is
     * used.
     * If the XKB_DEFAULT_VARIANT environment variable is set, it is used
     * as the default.  Otherwise the system default is used.
     */
    const(char) *variant;
    /**
     * A comma separated list of options, through which the user specifies
     * non-layout related preferences, like which key combinations are used
     * for switching layouts, or which key is the Compose key.
     *
     * If NULL, a default value is used.  If the empty string "", no
     * options are used.
     * If the XKB_DEFAULT_OPTIONS environment variable is set, it is used
     * as the default.  Otherwise the system default is used.
     */
    const(char) *options;
}

/**
 * @defgroup keysyms Keysyms
 * Utility functions related to keysyms.
 *
 * @{
 */

/**
 * @page keysym-transformations Keysym Transformations
 *
 * Keysym translation is subject to several "keysym transformations",
 * as described in the XKB specification.  These are:
 *
 * - Capitalization transformation.  If the Caps Lock modifier is
 *   active and was not consumed by the translation process, a single
 *   keysym is transformed to its upper-case form (if applicable).
 *   Similarly, the UTF-8/UTF-32 string produced is capitalized.
 *
 *   This is described in:
 *   http://www.x.org/releases/current/doc/kbproto/xkbproto.html#Interpreting_the_Lock_Modifier
 *
 * - Control transformation.  If the Control modifier is active and
 *   was not consumed by the translation process, the string produced
 *   is transformed to its matching ASCII control character (if
 *   applicable).  Keysyms are not affected.
 *
 *   This is described in:
 *   http://www.x.org/releases/current/doc/kbproto/xkbproto.html#Interpreting_the_Control_Modifier
 *
 * Each relevant function discusses which transformations it performs.
 *
 * These transformations are not applicable when a key produces multiple
 * keysyms.
 */


/**
 * Get the name of a keysym.
 *
 * For a description of how keysyms are named, see @ref xkb_keysym_t.
 *
 * @param[in]  keysym The keysym.
 * @param[out] buffer A string buffer to write the name into.
 * @param[in]  size   Size of the buffer.
 *
 * @warning If the buffer passed is too small, the string is truncated
 * (though still NUL-terminated); a size of at least 64 bytes is recommended.
 *
 * @returns The number of bytes in the name, excluding the NUL byte. If
 * the keysym is invalid, returns -1.
 *
 * You may check if truncation has occurred by comparing the return value
 * with the length of buffer, similarly to the snprintf(3) function.
 *
 * @sa xkb_keysym_t
 */
int
xkb_keysym_get_name(xkb_keysym_t keysym, char *buffer, size_t size);

/** Flags for xkb_keysym_from_name(). */
enum xkb_keysym_flags {
    /** Do not apply any flags. */
    XKB_KEYSYM_NO_FLAGS = 0,
    /** Find keysym by case-insensitive search. */
    XKB_KEYSYM_CASE_INSENSITIVE = (1 << 0)
}
alias XKB_KEYSYM_NO_FLAGS = xkb_keysym_flags.XKB_KEYSYM_NO_FLAGS;
alias XKB_KEYSYM_CASE_INSENSITIVE = xkb_keysym_flags.XKB_KEYSYM_CASE_INSENSITIVE;

/**
 * Get a keysym from its name.
 *
 * @param name The name of a keysym. See remarks in xkb_keysym_get_name();
 * this function will accept any name returned by that function.
 * @param flags A set of flags controlling how the search is done. If
 * invalid flags are passed, this will fail with XKB_KEY_NoSymbol.
 *
 * If you use the XKB_KEYSYM_CASE_INSENSITIVE flag and two keysym names
 * differ only by case, then the lower-case keysym is returned.  For
 * instance, for KEY_a and KEY_A, this function would return KEY_a for the
 * case-insensitive search.  If this functionality is needed, it is
 * recommended to first call this function without this flag; and if that
 * fails, only then to try with this flag, while possibly warning the user
 * he had misspelled the name, and might get wrong results.
 *
 * @returns The keysym. If the name is invalid, returns XKB_KEY_NoSymbol.
 *
 * @sa xkb_keysym_t
 */
xkb_keysym_t
xkb_keysym_from_name(const(char) *name, xkb_keysym_flags flags);

/**
 * Get the Unicode/UTF-8 representation of a keysym.
 *
 * @param[in]  keysym The keysym.
 * @param[out] buffer A buffer to write the UTF-8 string into.
 * @param[in]  size   The size of buffer.  Must be at least 7.
 *
 * @returns The number of bytes written to the buffer (including the
 * terminating byte).  If the keysym does not have a Unicode
 * representation, returns 0.  If the buffer is too small, returns -1.
 *
 * This function does not perform any @ref keysym-transformations.
 * Therefore, prefer to use xkb_state_key_get_utf8() if possible.
 *
 * @sa xkb_state_key_get_utf8()
 */
int
xkb_keysym_to_utf8(xkb_keysym_t keysym, char *buffer, size_t size);

/**
 * Get the Unicode/UTF-32 representation of a keysym.
 *
 * @returns The Unicode/UTF-32 representation of keysym, which is also
 * compatible with UCS-4.  If the keysym does not have a Unicode
 * representation, returns 0.
 *
 * This function does not perform any @ref keysym-transformations.
 * Therefore, prefer to use xkb_state_key_get_utf32() if possible.
 *
 * @sa xkb_state_key_get_utf32()
 */
uint
xkb_keysym_to_utf32(xkb_keysym_t keysym);

/** @} */

/**
 * @defgroup context Library Context
 * Creating, destroying and using library contexts.
 *
 * Every keymap compilation request must have a context associated with
 * it.  The context keeps around state such as the include path.
 *
 * @{
 */

/** Flags for context creation. */
enum xkb_context_flags {
    /** Do not apply any context flags. */
    XKB_CONTEXT_NO_FLAGS = 0,
    /** Create this context with an empty include path. */
    XKB_CONTEXT_NO_DEFAULT_INCLUDES = (1 << 0),
    /**
     * Don't take RMLVO names from the environment.
     * @since 0.3.0
     */
    XKB_CONTEXT_NO_ENVIRONMENT_NAMES = (1 << 1)
}
alias XKB_CONTEXT_NO_FLAGS = xkb_context_flags.XKB_CONTEXT_NO_FLAGS;
alias XKB_CONTEXT_NO_DEFAULT_INCLUDES = xkb_context_flags.XKB_CONTEXT_NO_DEFAULT_INCLUDES;
alias XKB_CONTEXT_NO_ENVIRONMENT_NAMES = xkb_context_flags.XKB_CONTEXT_NO_ENVIRONMENT_NAMES;

/**
 * Create a new context.
 *
 * @param flags Optional flags for the context, or 0.
 *
 * @returns A new context, or NULL on failure.
 *
 * The user may set some environment variables to affect default values in
 * the context. See e.g. xkb_context_set_log_level() and
 * xkb_context_set_log_verbosity().
 *
 * @memberof xkb_context
 */
xkb_context *
xkb_context_new(xkb_context_flags flags);

/**
 * Take a new reference on a context.
 *
 * @returns The passed in context.
 *
 * @memberof xkb_context
 */
xkb_context *
xkb_context_ref(xkb_context *context);

/**
 * Release a reference on a context, and possibly free it.
 *
 * @param context The context.  If it is NULL, this function does nothing.
 *
 * @memberof xkb_context
 */
void
xkb_context_unref(xkb_context *context);

/**
 * Store custom user data in the context.
 *
 * This may be useful in conjunction with xkb_context_set_log_fn() or other
 * callbacks.
 *
 * @memberof xkb_context
 */
void
xkb_context_set_user_data(xkb_context *context, void *user_data);

/**
 * Retrieves stored user data from the context.
 *
 * @returns The stored user data.  If the user data wasn't set, or the
 * passed in context is NULL, returns NULL.
 *
 * This may be useful to access private user data from callbacks like a
 * custom logging function.
 *
 * @memberof xkb_context
 **/
void *
xkb_context_get_user_data(xkb_context *context);

/** @} */

/**
 * @defgroup include-path Include Paths
 * Manipulating the include paths in a context.
 *
 * The include paths are the file-system paths that are searched when an
 * include statement is encountered during keymap compilation.
 * In most cases, the default include paths are sufficient.
 *
 * @{
 */

/**
 * Append a new entry to the context's include path.
 *
 * @returns 1 on success, or 0 if the include path could not be added or is
 * inaccessible.
 *
 * @memberof xkb_context
 */
int
xkb_context_include_path_append(xkb_context *context, const(char) *path);

/**
 * Append the default include paths to the context's include path.
 *
 * @returns 1 on success, or 0 if the primary include path could not be added.
 *
 * @memberof xkb_context
 */
int
xkb_context_include_path_append_default(xkb_context *context);

/**
 * Reset the context's include path to the default.
 *
 * Removes all entries from the context's include path, and inserts the
 * default paths.
 *
 * @returns 1 on success, or 0 if the primary include path could not be added.
 *
 * @memberof xkb_context
 */
int
xkb_context_include_path_reset_defaults(xkb_context *context);

/**
 * Remove all entries from the context's include path.
 *
 * @memberof xkb_context
 */
void
xkb_context_include_path_clear(xkb_context *context);

/**
 * Get the number of paths in the context's include path.
 *
 * @memberof xkb_context
 */
uint
xkb_context_num_include_paths(xkb_context *context);

/**
 * Get a specific include path from the context's include path.
 *
 * @returns The include path at the specified index.  If the index is
 * invalid, returns NULL.
 *
 * @memberof xkb_context
 */
const(char) *
xkb_context_include_path_get(xkb_context *context, uint index);

/** @} */

/**
 * @defgroup logging Logging Handling
 * Manipulating how logging from this library is handled.
 *
 * @{
 */

/** Specifies a logging level. */
enum xkb_log_level {
    XKB_LOG_LEVEL_CRITICAL = 10, /**< Log critical internal errors only. */
    XKB_LOG_LEVEL_ERROR = 20,    /**< Log all errors. */
    XKB_LOG_LEVEL_WARNING = 30,  /**< Log warnings and errors. */
    XKB_LOG_LEVEL_INFO = 40,     /**< Log information, warnings, and errors. */
    XKB_LOG_LEVEL_DEBUG = 50     /**< Log everything. */
}
alias XKB_LOG_LEVEL_CRITICAL = xkb_log_level.XKB_LOG_LEVEL_CRITICAL;
alias XKB_LOG_LEVEL_ERROR = xkb_log_level.XKB_LOG_LEVEL_ERROR;
alias XKB_LOG_LEVEL_WARNING = xkb_log_level.XKB_LOG_LEVEL_WARNING;
alias XKB_LOG_LEVEL_INFO = xkb_log_level.XKB_LOG_LEVEL_INFO;
alias XKB_LOG_LEVEL_DEBUG = xkb_log_level.XKB_LOG_LEVEL_DEBUG;

/**
 * Set the current logging level.
 *
 * @param context The context in which to set the logging level.
 * @param level   The logging level to use.  Only messages from this level
 * and below will be logged.
 *
 * The default level is XKB_LOG_LEVEL_ERROR.  The environment variable
 * XKB_LOG_LEVEL, if set in the time the context was created, overrides the
 * default value.  It may be specified as a level number or name.
 *
 * @memberof xkb_context
 */
void
xkb_context_set_log_level(xkb_context *context,
                          xkb_log_level level);

/**
 * Get the current logging level.
 *
 * @memberof xkb_context
 */
xkb_log_level
xkb_context_get_log_level(xkb_context *context);

/**
 * Sets the current logging verbosity.
 *
 * The library can generate a number of warnings which are not helpful to
 * ordinary users of the library.  The verbosity may be increased if more
 * information is desired (e.g. when developing a new keymap).
 *
 * The default verbosity is 0.  The environment variable XKB_LOG_VERBOSITY,
 * if set in the time the context was created, overrides the default value.
 *
 * @param context   The context in which to use the set verbosity.
 * @param verbosity The verbosity to use.  Currently used values are
 * 1 to 10, higher values being more verbose.  0 would result in no verbose
 * messages being logged.
 *
 * Most verbose messages are of level XKB_LOG_LEVEL_WARNING or lower.
 *
 * @memberof xkb_context
 */
void
xkb_context_set_log_verbosity(xkb_context *context, int verbosity);

/**
 * Get the current logging verbosity of the context.
 *
 * @memberof xkb_context
 */
int
xkb_context_get_log_verbosity(xkb_context *context);

/**
 * Set a custom function to handle logging messages.
 *
 * @param context The context in which to use the set logging function.
 * @param log_fn  The function that will be called for logging messages.
 * Passing NULL restores the default function, which logs to stderr.
 *
 * By default, log messages from this library are printed to stderr.  This
 * function allows you to replace the default behavior with a custom
 * handler.  The handler is only called with messages which match the
 * current logging level and verbosity settings for the context.
 * level is the logging level of the message.  @a format and @a args are
 * the same as in the vprintf(3) function.
 *
 * You may use xkb_context_set_user_data() on the context, and then call
 * xkb_context_get_user_data() from within the logging function to provide
 * it with additional private context.
 *
 * @memberof xkb_context
 */
private alias xkb_log_fn_t = void function(xkb_context *context,
                                      xkb_log_level level,
                                      const(char) *format, ...);
void
xkb_context_set_log_fn(xkb_context *context, xkb_log_fn_t log_fn);

/** @} */

/**
 * @defgroup keymap Keymap Creation
 * Creating and destroying keymaps.
 *
 * @{
 */

/** Flags for keymap compilation. */
enum xkb_keymap_compile_flags {
    /** Do not apply any flags. */
    XKB_KEYMAP_COMPILE_NO_FLAGS = 0
}
alias XKB_KEYMAP_COMPILE_NO_FLAGS = xkb_keymap_compile_flags.XKB_KEYMAP_COMPILE_NO_FLAGS;

/**
 * Create a keymap from RMLVO names.
 *
 * The primary keymap entry point: creates a new XKB keymap from a set of
 * RMLVO (Rules + Model + Layouts + Variants + Options) names.
 *
 * @param context The context in which to create the keymap.
 * @param names   The RMLVO names to use.  See xkb_rule_names.
 * @param flags   Optional flags for the keymap, or 0.
 *
 * @returns A keymap compiled according to the RMLVO names, or NULL if
 * the compilation failed.
 *
 * @sa xkb_rule_names
 * @memberof xkb_keymap
 */
xkb_keymap *
xkb_keymap_new_from_names(xkb_context *context,
                          const(xkb_rule_names) *names,
                          xkb_keymap_compile_flags flags);

/** The possible keymap formats. */
enum xkb_keymap_format {
    /** The current/classic XKB text format, as generated by xkbcomp -xkb. */
    XKB_KEYMAP_FORMAT_TEXT_V1 = 1
}
alias XKB_KEYMAP_FORMAT_TEXT_V1 = xkb_keymap_format.XKB_KEYMAP_FORMAT_TEXT_V1;

/**
 * Create a keymap from a keymap file.
 *
 * @param context The context in which to create the keymap.
 * @param file    The keymap file to compile.
 * @param format  The text format of the keymap file to compile.
 * @param flags   Optional flags for the keymap, or 0.
 *
 * @returns A keymap compiled from the given XKB keymap file, or NULL if
 * the compilation failed.
 *
 * The file must contain a complete keymap.  For example, in the
 * XKB_KEYMAP_FORMAT_TEXT_V1 format, this means the file must contain one
 * top level '%xkb_keymap' section, which in turn contains other required
 * sections.
 *
 * @memberof xkb_keymap
 */
xkb_keymap *
xkb_keymap_new_from_file(xkb_context *context, FILE *file,
                         xkb_keymap_format format,
                         xkb_keymap_compile_flags flags);

/**
 * Create a keymap from a keymap string.
 *
 * This is just like xkb_keymap_new_from_file(), but instead of a file, gets
 * the keymap as one enormous string.
 *
 * @see xkb_keymap_new_from_file()
 * @memberof xkb_keymap
 */
xkb_keymap *
xkb_keymap_new_from_string(xkb_context *context, const(char) *string,
                           xkb_keymap_format format,
                           xkb_keymap_compile_flags flags);

/**
 * Create a keymap from a memory buffer.
 *
 * This is just like xkb_keymap_new_from_string(), but takes a length argument
 * so the input string does not have to be zero-terminated.
 *
 * @see xkb_keymap_new_from_string()
 * @memberof xkb_keymap
 * @since 0.3.0
 */
xkb_keymap *
xkb_keymap_new_from_buffer(xkb_context *context, const(char) *buffer,
                           size_t length, xkb_keymap_format format,
                           xkb_keymap_compile_flags flags);

/**
 * Take a new reference on a keymap.
 *
 * @returns The passed in keymap.
 *
 * @memberof xkb_keymap
 */
xkb_keymap *
xkb_keymap_ref(xkb_keymap *keymap);

/**
 * Release a reference on a keymap, and possibly free it.
 *
 * @param keymap The keymap.  If it is NULL, this function does nothing.
 *
 * @memberof xkb_keymap
 */
void
xkb_keymap_unref(xkb_keymap *keymap);

/**
 * Get the keymap as a string in the format from which it was created.
 * @sa xkb_keymap_get_as_string()
 **/
enum XKB_KEYMAP_USE_ORIGINAL_FORMAT = cast(xkb_keymap_format)-1;

/**
 * Get the compiled keymap as a string.
 *
 * @param keymap The keymap to get as a string.
 * @param format The keymap format to use for the string.  You can pass
 * in the special value XKB_KEYMAP_USE_ORIGINAL_FORMAT to use the format
 * from which the keymap was originally created.
 *
 * @returns The keymap as a NUL-terminated string, or NULL if unsuccessful.
 *
 * The returned string may be fed back into xkb_map_new_from_string() to get
 * the exact same keymap (possibly in another process, etc.).
 *
 * The returned string is dynamically allocated and should be freed by the
 * caller.
 *
 * @memberof xkb_keymap
 */
char *
xkb_keymap_get_as_string(xkb_keymap *keymap,
                         xkb_keymap_format format);

/** @} */

/**
 * @defgroup components Keymap Components
 * Enumeration of state components in a keymap.
 *
 * @{
 */

/**
 * Get the minimum keycode in the keymap.
 *
 * @sa xkb_keycode_t
 * @memberof xkb_keymap
 * @since 0.3.1
 */
xkb_keycode_t
xkb_keymap_min_keycode(xkb_keymap *keymap);

/**
 * Get the maximum keycode in the keymap.
 *
 * @sa xkb_keycode_t
 * @memberof xkb_keymap
 * @since 0.3.1
 */
xkb_keycode_t
xkb_keymap_max_keycode(xkb_keymap *keymap);

/**
 * The iterator used by xkb_keymap_key_for_each().
 *
 * @sa xkb_keymap_key_for_each
 * @memberof xkb_keymap
 * @since 0.3.1
 */
alias xkb_keymap_key_iter_t =
        void function (xkb_keymap *keymap, xkb_keycode_t key, void *data);

/**
 * Run a specified function for every valid keycode in the keymap.  If a
 * keymap is sparse, this function may be called fewer than
 * (max_keycode - min_keycode + 1) times.
 *
 * @sa xkb_keymap_min_keycode() xkb_keymap_max_keycode() xkb_keycode_t
 * @memberof xkb_keymap
 * @since 0.3.1
 */
void
xkb_keymap_key_for_each(xkb_keymap *keymap, xkb_keymap_key_iter_t iter,
                        void *data);

/**
 * Get the number of modifiers in the keymap.
 *
 * @sa xkb_mod_index_t
 * @memberof xkb_keymap
 */
xkb_mod_index_t
xkb_keymap_num_mods(xkb_keymap *keymap);

/**
 * Get the name of a modifier by index.
 *
 * @returns The name.  If the index is invalid, returns NULL.
 *
 * @sa xkb_mod_index_t
 * @memberof xkb_keymap
 */
const(char) *
xkb_keymap_mod_get_name(xkb_keymap *keymap, xkb_mod_index_t idx);

/**
 * Get the index of a modifier by name.
 *
 * @returns The index.  If no modifier with this name exists, returns
 * XKB_MOD_INVALID.
 *
 * @sa xkb_mod_index_t
 * @memberof xkb_keymap
 */
xkb_mod_index_t
xkb_keymap_mod_get_index(xkb_keymap *keymap, const(char) *name);

/**
 * Get the number of layouts in the keymap.
 *
 * @sa xkb_layout_index_t xkb_rule_names xkb_keymap_num_layouts_for_key()
 * @memberof xkb_keymap
 */
xkb_layout_index_t
xkb_keymap_num_layouts(xkb_keymap *keymap);

/**
 * Get the name of a layout by index.
 *
 * @returns The name.  If the index is invalid, or the layout does not have
 * a name, returns NULL.
 *
 * @sa xkb_layout_index_t
 * @memberof xkb_keymap
 */
const(char) *
xkb_keymap_layout_get_name(xkb_keymap *keymap, xkb_layout_index_t idx);

/**
 * Get the index of a layout by name.
 *
 * @returns The index.  If no layout exists with this name, returns
 * XKB_LAYOUT_INVALID.  If more than one layout in the keymap has this name,
 * returns the lowest index among them.
 *
 * @memberof xkb_keymap
 */
xkb_layout_index_t
xkb_keymap_layout_get_index(xkb_keymap *keymap, const(char) *name);

/**
 * Get the number of LEDs in the keymap.
 *
 * @warning The range [ 0...xkb_keymap_num_leds() ) includes all of the LEDs
 * in the keymap, but may also contain inactive LEDs.  When iterating over
 * this range, you need the handle this case when calling functions such as
 * xkb_keymap_led_get_name() or xkb_state_led_index_is_active().
 *
 * @sa xkb_led_index_t
 * @memberof xkb_keymap
 */
xkb_led_index_t
xkb_keymap_num_leds(xkb_keymap *keymap);

/**
 * Get the name of a LED by index.
 *
 * @returns The name.  If the index is invalid, returns NULL.
 *
 * @memberof xkb_keymap
 */
const(char) *
xkb_keymap_led_get_name(xkb_keymap *keymap, xkb_led_index_t idx);

/**
 * Get the index of a LED by name.
 *
 * @returns The index.  If no LED with this name exists, returns
 * XKB_LED_INVALID.
 *
 * @memberof xkb_keymap
 */
xkb_led_index_t
xkb_keymap_led_get_index(xkb_keymap *keymap, const(char) *name);

/**
 * Get the number of layouts for a specific key.
 *
 * This number can be different from xkb_keymap_num_layouts(), but is always
 * smaller.  It is the appropriate value to use when iterating over the
 * layouts of a key.
 *
 * @sa xkb_layout_index_t
 * @memberof xkb_keymap
 */
xkb_layout_index_t
xkb_keymap_num_layouts_for_key(xkb_keymap *keymap, xkb_keycode_t key);

/**
 * Get the number of shift levels for a specific key and layout.
 *
 * If @c layout is out of range for this key (that is, larger or equal to
 * the value returned by xkb_keymap_num_layouts_for_key()), it is brought
 * back into range in a manner consistent with xkb_state_key_get_layout().
 *
 * @sa xkb_level_index_t
 * @memberof xkb_keymap
 */
xkb_level_index_t
xkb_keymap_num_levels_for_key(xkb_keymap *keymap, xkb_keycode_t key,
                              xkb_layout_index_t layout);

/**
 * Get the keysyms obtained from pressing a key in a given layout and
 * shift level.
 *
 * This function is like xkb_state_key_get_syms(), only the layout and
 * shift level are not derived from the keyboard state but are instead
 * specified explicitly.
 *
 * @param[in] keymap    The keymap.
 * @param[in] key       The keycode of the key.
 * @param[in] layout    The layout for which to get the keysyms.
 * @param[in] level     The shift level in the layout for which to get the
 * keysyms. This must be smaller than:
 * @code xkb_keymap_num_levels_for_key(keymap, key) @endcode
 * @param[out] syms_out An immutable array of keysyms corresponding to the
 * key in the given layout and shift level.
 *
 * If @c layout is out of range for this key (that is, larger or equal to
 * the value returned by xkb_keymap_num_layouts_for_key()), it is brought
 * back into range in a manner consistent with xkb_state_key_get_layout().
 *
 * @returns The number of keysyms in the syms_out array.  If no keysyms
 * are produced by the key in the given layout and shift level, returns 0
 * and sets syms_out to NULL.
 *
 * @sa xkb_state_key_get_syms()
 * @memberof xkb_keymap
 */
int
xkb_keymap_key_get_syms_by_level(xkb_keymap *keymap,
                                 xkb_keycode_t key,
                                 xkb_layout_index_t layout,
                                 xkb_level_index_t level,
                                 const(xkb_keysym_t*) *syms_out);

/**
 * Determine whether a key should repeat or not.
 *
 * A keymap may specify different repeat behaviors for different keys.
 * Most keys should generally exhibit repeat behavior; for example, holding
 * the 'a' key down in a text editor should normally insert a single 'a'
 * character every few milliseconds, until the key is released.  However,
 * there are keys which should not or do not need to be repeated.  For
 * example, repeating modifier keys such as Left/Right Shift or Caps Lock
 * is not generally useful or desired.
 *
 * @returns 1 if the key should repeat, 0 otherwise.
 *
 * @memberof xkb_keymap
 */
int
xkb_keymap_key_repeats(xkb_keymap *keymap, xkb_keycode_t key);

/** @} */

/**
 * @defgroup state Keyboard State
 * Creating, destroying and manipulating keyboard state objects.
 *
 * @{
 */

/**
 * Create a new keyboard state object.
 *
 * @param keymap The keymap which the state will use.
 *
 * @returns A new keyboard state object, or NULL on failure.
 *
 * @memberof xkb_state
 */
xkb_state *
xkb_state_new(xkb_keymap *keymap);

/**
 * Take a new reference on a keyboard state object.
 *
 * @returns The passed in object.
 *
 * @memberof xkb_state
 */
xkb_state *
xkb_state_ref(xkb_state *state);

/**
 * Release a reference on a keybaord state object, and possibly free it.
 *
 * @param state The state.  If it is NULL, this function does nothing.
 *
 * @memberof xkb_state
 */
void
xkb_state_unref(xkb_state *state);

/**
 * Get the keymap which a keyboard state object is using.
 *
 * @returns The keymap which was passed to xkb_state_new() when creating
 * this state object.
 *
 * This function does not take a new reference on the keymap; you must
 * explicitly reference it yourself if you plan to use it beyond the
 * lifetime of the state.
 *
 * @memberof xkb_state
 */
xkb_keymap *
xkb_state_get_keymap(xkb_state *state);

/** Specifies the direction of the key (press / release). */
enum xkb_key_direction {
    XKB_KEY_UP,   /**< The key was released. */
    XKB_KEY_DOWN  /**< The key was pressed. */
}
alias XKB_KEY_UP = xkb_key_direction.XKB_KEY_UP;
alias XKB_KEY_DOWN = xkb_key_direction.XKB_KEY_DOWN;

/**
 * Modifier and layout types for state objects.  This enum is bitmaskable,
 * e.g. (XKB_STATE_MODS_DEPRESSED | XKB_STATE_MODS_LATCHED) is valid to
 * exclude locked modifiers.
 *
 * In XKB, the DEPRESSED components are also known as 'base'.
 */
enum xkb_state_component {
    /** Depressed modifiers, i.e. a key is physically holding them. */
    XKB_STATE_MODS_DEPRESSED = (1 << 0),
    /** Latched modifiers, i.e. will be unset after the next non-modifier
     *  key press. */
    XKB_STATE_MODS_LATCHED = (1 << 1),
    /** Locked modifiers, i.e. will be unset after the key provoking the
     *  lock has been pressed again. */
    XKB_STATE_MODS_LOCKED = (1 << 2),
    /** Effective modifiers, i.e. currently active and affect key
     *  processing (derived from the other state components).
     *  Use this unless you explictly care how the state came about. */
    XKB_STATE_MODS_EFFECTIVE = (1 << 3),
    /** Depressed layout, i.e. a key is physically holding it. */
    XKB_STATE_LAYOUT_DEPRESSED = (1 << 4),
    /** Latched layout, i.e. will be unset after the next non-modifier
     *  key press. */
    XKB_STATE_LAYOUT_LATCHED = (1 << 5),
    /** Locked layout, i.e. will be unset after the key provoking the lock
     *  has been pressed again. */
    XKB_STATE_LAYOUT_LOCKED = (1 << 6),
    /** Effective layout, i.e. currently active and affects key processing
     *  (derived from the other state components).
     *  Use this unless you explictly care how the state came about. */
    XKB_STATE_LAYOUT_EFFECTIVE = (1 << 7),
    /** LEDs (derived from the other state components). */
    XKB_STATE_LEDS = (1 << 8)
}
alias XKB_STATE_MODS_DEPRESSED = xkb_state_component.XKB_STATE_MODS_DEPRESSED;
alias XKB_STATE_MODS_LATCHED = xkb_state_component.XKB_STATE_MODS_LATCHED;
alias XKB_STATE_MODS_LOCKED = xkb_state_component.XKB_STATE_MODS_LOCKED;
alias XKB_STATE_MODS_EFFECTIVE = xkb_state_component.XKB_STATE_MODS_EFFECTIVE;
alias XKB_STATE_LAYOUT_DEPRESSED = xkb_state_component.XKB_STATE_LAYOUT_DEPRESSED;
alias XKB_STATE_LAYOUT_LATCHED = xkb_state_component.XKB_STATE_LAYOUT_LATCHED;
alias XKB_STATE_LAYOUT_LOCKED = xkb_state_component.XKB_STATE_LAYOUT_LOCKED;
alias XKB_STATE_LAYOUT_EFFECTIVE = xkb_state_component.XKB_STATE_LAYOUT_EFFECTIVE;

/**
 * Update the keyboard state to reflect a given key being pressed or
 * released.
 *
 * This entry point is intended for programs which track the keyboard state
 * explictly (like an evdev client).  If the state is serialized to you by
 * a master process (like a Wayland compositor) using functions like
 * xkb_state_serialize_mods(), you should use xkb_state_update_mask() instead.
 * The two functins should not generally be used together.
 *
 * A series of calls to this function should be consistent; that is, a call
 * with XKB_KEY_DOWN for a key should be matched by an XKB_KEY_UP; if a key
 * is pressed twice, it should be released twice; etc. Otherwise (e.g. due
 * to missed input events), situations like "stuck modifiers" may occur.
 *
 * This function is often used in conjunction with the function
 * xkb_state_key_get_syms() (or xkb_state_key_get_one_sym()), for example,
 * when handling a key event.  In this case, you should prefer to get the
 * keysyms *before* updating the key, such that the keysyms reported for
 * the key event are not affected by the event itself.  This is the
 * conventional behavior.
 *
 * @returns A mask of state components that have changed as a result of
 * the update.  If nothing in the state has changed, returns 0.
 *
 * @memberof xkb_state
 *
 * @sa xkb_state_update_mask()
 */
xkb_state_component
xkb_state_update_key(xkb_state *state, xkb_keycode_t key,
                     xkb_key_direction direction);

/**
 * Update a keyboard state from a set of explicit masks.
 *
 * This entry point is intended for window systems and the like, where a
 * master process holds an xkb_state, then serializes it over a wire
 * protocol, and clients then use the serialization to feed in to their own
 * xkb_state.
 *
 * All parameters must always be passed, or the resulting state may be
 * incoherent.
 *
 * The serialization is lossy and will not survive round trips; it must only
 * be used to feed slave state objects, and must not be used to update the
 * master state.
 *
 * If you do not fit the description above, you should use
 * xkb_state_update_key() instead.  The two functions should not generally be
 * used together.
 *
 * @returns A mask of state components that have changed as a result of
 * the update.  If nothing in the state has changed, returns 0.
 *
 * @memberof xkb_state
 *
 * @sa xkb_state_component
 * @sa xkb_state_update_key
 */
xkb_state_component
xkb_state_update_mask(xkb_state *state,
                      xkb_mod_mask_t depressed_mods,
                      xkb_mod_mask_t latched_mods,
                      xkb_mod_mask_t locked_mods,
                      xkb_layout_index_t depressed_layout,
                      xkb_layout_index_t latched_layout,
                      xkb_layout_index_t locked_layout);

/**
 * Get the keysyms obtained from pressing a particular key in a given
 * keyboard state.
 *
 * Get the keysyms for a key according to the current active layout,
 * modifiers and shift level for the key, as determined by a keyboard
 * state.
 *
 * @param[in]  state    The keyboard state object.
 * @param[in]  key      The keycode of the key.
 * @param[out] syms_out An immutable array of keysyms corresponding the
 * key in the given keyboard state.
 *
 * As an extension to XKB, this function can return more than one keysym.
 * If you do not want to handle this case, you can use
 * xkb_state_key_get_one_sym() for a simpler interface.
 *
 * This function does not perform any @ref keysym-transformations.
 * (This might change).
 *
 * @returns The number of keysyms in the syms_out array.  If no keysyms
 * are produced by the key in the given keyboard state, returns 0 and sets
 * syms_out to NULL.
 *
 * @memberof xkb_state
 */
int
xkb_state_key_get_syms(xkb_state *state, xkb_keycode_t key,
                       const(xkb_keysym_t*) *syms_out);

/**
 * Get the Unicode/UTF-8 string obtained from pressing a particular key
 * in a given keyboard state.
 *
 * @param[in]  state  The keyboard state object.
 * @param[in]  key    The keycode of the key.
 * @param[out] buffer A buffer to write the string into.
 * @param[in]  size   Size of the buffer.
 *
 * @warning If the buffer passed is too small, the string is truncated
 * (though still NUL-terminated).
 *
 * @returns The number of bytes required for the string, excluding the
 * NUL byte.  If there is nothing to write, returns 0.
 *
 * You may check if truncation has occurred by comparing the return value
 * with the size of @p buffer, similarly to the snprintf(3) function.
 * You may safely pass NULL and 0 to @p buffer and @p size to find the
 * required size (without the NUL-byte).
 *
 * This function performs Capitalization and Control @ref
 * keysym-transformations.
 *
 * @memberof xkb_state
 * @since 0.4.1
 */
int
xkb_state_key_get_utf8(xkb_state *state, xkb_keycode_t key,
                       char *buffer, size_t size);

/**
 * Get the Unicode/UTF-32 codepoint obtained from pressing a particular
 * key in a a given keyboard state.
 *
 * @returns The UTF-32 representation for the key, if it consists of only
 * a single codepoint.  Otherwise, returns 0.
 *
 * This function performs Capitalization and Control @ref
 * keysym-transformations.
 *
 * @memberof xkb_state
 * @since 0.4.1
 */
uint
xkb_state_key_get_utf32(xkb_state *state, xkb_keycode_t key);

/**
 * Get the single keysym obtained from pressing a particular key in a
 * given keyboard state.
 *
 * This function is similar to xkb_state_key_get_syms(), but intended
 * for users which cannot or do not want to handle the case where
 * multiple keysyms are returned (in which case this function is
 * preferred).
 *
 * @returns The keysym.  If the key does not have exactly one keysym,
 * returns XKB_KEY_NoSymbol
 *
 * This function performs Capitalization @ref keysym-transformations.
 *
 * @sa xkb_state_key_get_syms()
 * @memberof xkb_state
 */
xkb_keysym_t
xkb_state_key_get_one_sym(xkb_state *state, xkb_keycode_t key);

/**
 * Get the effective layout index for a key in a given keyboard state.
 *
 * @returns The layout index for the key in the given keyboard state.  If
 * the given keycode is invalid, or if the key is not included in any
 * layout at all, returns XKB_LAYOUT_INVALID.
 *
 * @invariant If the returned layout is valid, the following always holds:
 * @code
 * xkb_state_key_get_layout(state, key) < xkb_keymap_num_layouts_for_key(keymap, key)
 * @endcode
 *
 * @memberof xkb_state
 */
xkb_layout_index_t
xkb_state_key_get_layout(xkb_state *state, xkb_keycode_t key);

/**
 * Get the effective shift level for a key in a given keyboard state and
 * layout.
 *
 * @param state The keyboard state.
 * @param key The keycode of the key.
 * @param layout The layout for which to get the shift level.  This must be
 * smaller than:
 * @code xkb_keymap_num_layouts_for_key(keymap, key) @endcode
 * usually it would be:
 * @code xkb_state_key_get_layout(state, key) @endcode
 *
 * @return The shift level index.  If the key or layout are invalid,
 * returns XKB_LEVEL_INVALID.
 *
 * @invariant If the returned level is valid, the following always holds:
 * @code
 * xkb_state_key_get_level(state, key, layout) < xkb_keymap_num_levels_for_key(keymap, key, layout)
 * @endcode
 *
 * @memberof xkb_state
 */
xkb_level_index_t
xkb_state_key_get_level(xkb_state *state, xkb_keycode_t key,
                        xkb_layout_index_t layout);

/**
 * Match flags for xkb_state_mod_indices_are_active() and
 * xkb_state_mod_names_are_active(), specifying the conditions for a
 * successful match.  XKB_STATE_MATCH_NON_EXCLUSIVE is bitmaskable with
 * the other modes.
 */
enum xkb_state_match {
    /** Returns true if any of the modifiers are active. */
    XKB_STATE_MATCH_ANY = (1 << 0),
    /** Returns true if all of the modifiers are active. */
    XKB_STATE_MATCH_ALL = (1 << 1),
    /** Makes matching non-exclusive, i.e. will not return false if a
     *  modifier not specified in the arguments is active. */
    XKB_STATE_MATCH_NON_EXCLUSIVE = (1 << 16)
}
alias XKB_STATE_MATCH_ANY = xkb_state_match.XKB_STATE_MATCH_ANY;
alias XKB_STATE_MATCH_ALL = xkb_state_match.XKB_STATE_MATCH_ALL;
alias XKB_STATE_MATCH_NON_EXCLUSIVE = xkb_state_match.XKB_STATE_MATCH_NON_EXCLUSIVE;

/**
 * The counterpart to xkb_state_update_mask for modifiers, to be used on
 * the server side of serialization.
 *
 * @param state      The keyboard state.
 * @param components A mask of the modifier state components to serialize.
 * State components other than XKB_STATE_MODS_* are ignored.
 * If XKB_STATE_MODS_EFFECTIVE is included, all other state components are
 * ignored.
 *
 * @returns A xkb_mod_mask_t representing the given components of the
 * modifier state.
 *
 * This function should not be used in regular clients; please use the
 * xkb_state_mod_*_is_active API instead.
 *
 * @memberof xkb_state
 */
xkb_mod_mask_t
xkb_state_serialize_mods(xkb_state *state,
                         xkb_state_component components);

/**
 * The counterpart to xkb_state_update_mask for layouts, to be used on
 * the server side of serialization.
 *
 * @param state      The keyboard state.
 * @param components A mask of the layout state components to serialize.
 * State components other than XKB_STATE_LAYOUT_* are ignored.
 * If XKB_STATE_LAYOUT_EFFECTIVE is included, all other state components are
 * ignored.
 *
 * @returns A layout index representing the given components of the
 * layout state.
 *
 * This function should not be used in regular clients; please use the
 * xkb_state_layout_*_is_active API instead.
 *
 * @memberof xkb_state
 */
xkb_layout_index_t
xkb_state_serialize_layout(xkb_state *state,
                           xkb_state_component components);

/**
 * Test whether a modifier is active in a given keyboard state by name.
 *
 * @returns 1 if the modifier is active, 0 if it is not.  If the modifier
 * name does not exist in the keymap, returns -1.
 *
 * @memberof xkb_state
 */
int
xkb_state_mod_name_is_active(xkb_state *state, const(char) *name,
                             xkb_state_component type);

/**
 * Test whether a set of modifiers are active in a given keyboard state by
 * name.
 *
 * @param state The keyboard state.
 * @param type  The component of the state against which to match the
 * given modifiers.
 * @param match The manner by which to match the state against the
 * given modifiers.
 * @param ...   The set of of modifier names to test, terminated by a NULL
 * argument (sentinel).
 *
 * @returns 1 if the modifiers are active, 0 if they are not.  If any of
 * the modifier names do not exist in the keymap, returns -1.
 *
 * @memberof xkb_state
 */
int
xkb_state_mod_names_are_active(xkb_state *state,
                               xkb_state_component type,
                               xkb_state_match match,
                               ...);

/**
 * Test whether a modifier is active in a given keyboard state by index.
 *
 * @returns 1 if the modifier is active, 0 if it is not.  If the modifier
 * index is invalid in the keymap, returns -1.
 *
 * @memberof xkb_state
 */
int
xkb_state_mod_index_is_active(xkb_state *state, xkb_mod_index_t idx,
                              xkb_state_component type);

/**
 * Test whether a set of modifiers are active in a given keyboard state by
 * index.
 *
 * @param state The keyboard state.
 * @param type  The component of the state against which to match the
 * given modifiers.
 * @param match The manner by which to match the state against the
 * given modifiers.
 * @param ...   The set of of modifier indices to test, terminated by a
 * XKB_MOD_INVALID argument (sentinel).
 *
 * @returns 1 if the modifiers are active, 0 if they are not.  If any of
 * the modifier indices are invalid in the keymap, returns -1.
 *
 * @memberof xkb_state
 */
int
xkb_state_mod_indices_are_active(xkb_state *state,
                                 xkb_state_component type,
                                 xkb_state_match match,
                                 ...);

/**
 * @page consumed-modifiers Consumed Modifiers
 * @parblock
 *
 * Some functions, like xkb_state_key_get_syms(), look at the state of
 * the modifiers in the keymap and derive from it the correct shift level
 * to use for the key.  For example, in a US layout, pressing the key
 * labeled \<A\> while the Shift modifier is active, generates the keysym
 * 'A'.  In this case, the Shift modifier is said to be "consumed".
 * However, the Num Lock modifier does not affect this translation at all,
 * even if it is active, so it is not consumed by this translation.
 *
 * It may be desirable for some application to not reuse consumed modifiers
 * for further processing, e.g. for hotkeys or keyboard shortcuts.  To
 * understand why, consider some requirements from a standard shortcut
 * mechanism, and how they are implemented:
 *
 * 1. The shortcut's modifiers must match exactly to the state.  For
 *    example, it is possible to bind separate actions to \<Alt\>\<Tab\>
 *    and to \<Alt\>\<Shift\>\<Tab\>.  Further, if only \<Alt\>\<Tab\> is
 *    bound to an action, pressing \<Alt\>\<Shift\>\<Tab\> should not
 *    trigger the shortcut.
 *    Effectively, this means that the modifiers are compared using the
 *    equality operator (==).
 *
 * 2. Only relevant modifiers are considered for the matching.  For example,
 *    Caps Lock and Num Lock should not generally affect the matching, e.g.
 *    when matching \<Alt\>\<Tab\> against the state, it does not matter
 *    whether Num Lock is active or not.  These relevant, or "significant",
 *    modifiers usually include Alt, Control, Shift, Super and similar.
 *    Effectively, this means that non-significant modifiers are masked out,
 *    before doing the comparison as described above.
 *
 * 3. The matching must be independent of the layout/keymap.  For example,
 *    the \<Plus\> (+) symbol is found on the first level on some layouts,
 *    but requires holding Shift on others.  If you simply bind the action
 *    to the \<Plus\> keysym, it would work for the unshifted kind, but
 *    not for the others, because the match against Shift would fail.  If
 *    you bind the action to \<Shift\>\<Plus\>, only the shifted kind would
 *    work.  So what is needed is to recognize that Shift is used up in the
 *    translation of the keysym itself, and therefore should not be included
 *    in the matching.
 *    Effectively, this means that consumed modifiers (Shift in this example)
 *    are masked out as well, before doing the comparison.
 *
 * In summary, this is how the matching would be performed:
 * @code
 *   (keysym == shortcut_keysym) &&
 *   ((state_mods & ~consumed_mods & significant_mods) == shortcut_mods)
 * @endcode
 *
 * @c state_mods are the modifiers reported by
 * xkb_state_mod_index_is_active() and similar functions.
 * @c consumed_mods are the modifiers reported by
 * xkb_state_mod_index_is_consumed() and similar functions.
 * @c significant_mods are decided upon by the application/toolkit/user;
 * it is up to them to decide whether these are configurable or hard-coded.
 *
 * @endparblock
 */

/**
 * Test whether a modifier is consumed by keyboard state translation for
 * a key.
 *
 * @returns 1 if the modifier is consumed, 0 if it is not.  If the modifier
 * index is not valid in the keymap, returns -1.
 *
 * @sa xkb_state_mod_mask_remove_consumed()
 * @sa xkb_state_key_get_consumed_mods()
 * @memberof xkb_state
 */
int
xkb_state_mod_index_is_consumed(xkb_state *state, xkb_keycode_t key,
                                xkb_mod_index_t idx);

/**
 * Remove consumed modifiers from a modifier mask for a key.
 *
 * Takes the given modifier mask, and removes all modifiers which are
 * consumed for that particular key (as in xkb_state_mod_index_is_consumed()).
 *
 * @sa xkb_state_mod_index_is_consumed()
 * @memberof xkb_state
 */
xkb_mod_mask_t
xkb_state_mod_mask_remove_consumed(xkb_state *state, xkb_keycode_t key,
                                   xkb_mod_mask_t mask);

/**
 * Get the mask of modifiers consumed by translating a given key.
 *
 * @returns a mask of the consumed modifiers.
 *
 * @sa xkb_state_mod_index_is_consumed()
 * @memberof xkb_state
 * @since 0.4.1
 */
xkb_mod_mask_t
xkb_state_key_get_consumed_mods(xkb_state *state, xkb_keycode_t key);

/**
 * Test whether a layout is active in a given keyboard state by name.
 *
 * @returns 1 if the layout is active, 0 if it is not.  If no layout with
 * this name exists in the keymap, return -1.
 *
 * If multiple layouts in the keymap have this name, the one with the lowest
 * index is tested.
 *
 * @sa xkb_layout_index_t
 * @memberof xkb_state
 */
int
xkb_state_layout_name_is_active(xkb_state *state, const(char) *name,
                                xkb_state_component type);

/**
 * Test whether a layout is active in a given keyboard state by index.
 *
 * @returns 1 if the layout is active, 0 if it is not.  If the layout index
 * is not valid in the keymap, returns -1.
 *
 * @sa xkb_layout_index_t
 * @memberof xkb_state
 */
int
xkb_state_layout_index_is_active(xkb_state *state,
                                 xkb_layout_index_t idx,
                                 xkb_state_component type);

/**
 * Test whether a LED is active in a given keyboard state by name.
 *
 * @returns 1 if the LED is active, 0 if it not.  If no LED with this name
 * exists in the keymap, returns -1.
 *
 * @sa xkb_led_index_t
 * @memberof xkb_state
 */
int
xkb_state_led_name_is_active(xkb_state *state, const(char) *name);

/**
 * Test whether a LED is active in a given keyboard state by index.
 *
 * @returns 1 if the LED is active, 0 if it not.  If the LED index is not
 * valid in the keymap, returns -1.
 *
 * @sa xkb_led_index_t
 * @memberof xkb_state
 */
int
xkb_state_led_index_is_active(xkb_state *state, xkb_led_index_t idx);