114 lines
4.4 KiB
Groff
114 lines
4.4 KiB
Groff
'\" t
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.\" Copyright 1999 Oracle and/or its affiliates. All rights reserved.
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.\"
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.\" Permission is hereby granted, free of charge, to any person obtaining a
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.\" copy of this software and associated documentation files (the "Software"),
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.\" to deal in the Software without restriction, including without limitation
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.\" the rights to use, copy, modify, merge, publish, distribute, sublicense,
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.\" and/or sell copies of the Software, and to permit persons to whom the
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.\" Software is furnished to do so, subject to the following conditions:
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.\"
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.\" The above copyright notice and this permission notice (including the next
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.\" paragraph) shall be included in all copies or substantial portions of the
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.\" Software.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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.\" IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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.\" FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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.\" THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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.\" LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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.\" FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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.\" DEALINGS IN THE SOFTWARE.
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.\"
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.TH XkbKeyNumActions __libmansuffix__ __xorgversion__ "XKB FUNCTIONS"
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.SH NAME
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XkbKeyNumActions \- Computes the number of actions associated with the key corresponding to
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keycode
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.SH SYNOPSIS
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.HP
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.B int XkbKeyNumActions
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.BI "(\^XkbDescPtr " "xkb" "\^,"
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.BI "KeyCode " "keycode" "\^);"
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.if n .ti +5n
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.if t .ti +.5i
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.SH ARGUMENTS
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.TP
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.I \- xkb
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Xkb description of interest
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.TP
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.I \- keycode
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keycode of interest
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.SH DESCRIPTION
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.LP
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A key action defines the effect key presses and releases have on the internal state of the
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server. For example, the expected key action associated with pressing the Shift key is to set
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the Shift modifier. There is zero or one key action associated with each keysym bound to each
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key.
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Just as the entire list of key symbols for the keyboard mapping is held in the
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.I syms
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field of the client map, the entire list of key actions for the keyboard mapping is held in the
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.I acts
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array of the server map. The total size of
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.I acts
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is specified by
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.I size_acts,
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and the number of entries is specified by
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.I num_acts.
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The
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.I key_acts
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array, indexed by keycode, describes the actions associated with a key. The
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.I key_acts
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array has
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.I min_key_code
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unused entries at the start to allow direct indexing using a keycode. If a
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.I key_acts
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entry is zero, it means the key does not have any actions associated with it. If an entry is not
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zero, the entry represents an index into the
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.I acts
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field of the server map, much as the
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.I offset
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field of a KeySymMapRec structure is an index into the
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.I syms
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field of the client map.
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The reason the
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.I acts
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field is a linear list of XkbActions is to reduce the memory consumption associated with a
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keymap. Because Xkb allows individual keys to have multiple shift levels and a different number
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of groups per key, a single two-dimensional array of KeySyms would potentially be very large and
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sparse. Instead, Xkb provides a small two-dimensional array of XkbActions for each key. To store
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all of these individual arrays, Xkb concatenates each array together in the
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.I acts
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field of the server map.
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The key action structures consist only of fields of type char or unsigned char. This is done to
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optimize data transfer when the server sends bytes over the wire. If the fields are anything but
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bytes, the server has to sift through all of the actions and swap any nonbyte fields. Because
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they consist of nothing but bytes, it can just copy them out.
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.I XkbKeyNumActions
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computes the number of actions associated with the key corresponding to
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.I keycode.
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This should be the same value as the result of
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.I XkbKeyNumSyms.
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.SH STRUCTURES
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.LP
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The KeySymMapRec structure is defined as follows:
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.nf
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#define XkbNumKbdGroups 4
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#define XkbMaxKbdGroup (XkbNumKbdGroups-1)
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typedef struct { /\(** map to keysyms for a single keycode */
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unsigned char kt_index[XkbNumKbdGroups]; /\(** key type index for each group */
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unsigned char group_info; /\(** # of groups and out of range group handling */
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unsigned char width; /\(** max # of shift levels for key */
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unsigned short offset; /\(** index to keysym table in syms array */
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} XkbSymMapRec, *XkbSymMapPtr;
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.fi
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.SH "SEE ALSO"
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.BR XkbKeyNumSyms (__libmansuffix__)
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