diff options
Diffstat (limited to 'specs/ch01.xml')
| -rw-r--r-- | specs/ch01.xml | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/specs/ch01.xml b/specs/ch01.xml new file mode 100644 index 0000000..7bf0ef4 --- /dev/null +++ b/specs/ch01.xml @@ -0,0 +1,101 @@ +<chapter id='overview'> +<title>Overview</title> +<para> +This extension provides a number of new capabilities and controls for +text keyboards. +</para> + +<para> +The core X protocol specifies the ways that the <emphasis> +Shift</emphasis> +, <emphasis> +Control</emphasis> + and <emphasis> +Lock</emphasis> + modifiers and the modifiers bound to the <emphasis> +Mode_switch</emphasis> + or <emphasis> +Num_Lock</emphasis> + keysyms interact to generate keysyms and characters. The core protocol also +allows users to specify that a key affects one or more modifiers. This behavior +is simple and fairly flexible, but it has a number of limitations that make it +difficult or impossible to properly support many common varieties of keyboard +behavior. The limitations of core protocol support for keyboards include: +</para> + +<itemizedlist> +<listitem> + <para>Use of a single, uniform, four-symbol mapping for all keyboard keys +makes it difficult to properly support keyboard overlays, PC-style break keys +or keyboards that comply with ISO9995 or a host of other national and +international standards. + </para> +</listitem> +<listitem> + <para>Use of a modifier to specify a second keyboard group has side-effects +that wreak havoc with client grabs and X toolkit translations and limit us to +two keyboard groups. + </para> +</listitem> +<listitem> + <para>Poorly specified locking key behavior requires X servers to look for a +few "magic" keysyms to determine which keys should lock when pressed. This +leads to incompatibilities between X servers with no way for clients to detect +implementation differences. + </para> +</listitem> +<listitem> + <para>Poorly specified capitalization and control behavior requires +modifications to X library source code to support new character sets or locales +and can lead to incompatibilities between system-wide and X library +capitalization behavior. + </para> +</listitem> +<listitem> + <para>Limited interactions between modifiers specified by the core protocol +make many common keyboard behaviors difficult or impossible to implement. For +example, there is no reliable way to indicate whether or not using shift should +"cancel" the lock modifier. + </para> +</listitem> +<listitem> + <para>The lack of any explicit descriptions for indicators, most modifiers +and other aspects of the keyboard appearance requires clients that wish to +clearly describe the keyboard to a user to resort to a mishmash of prior +knowledge and heuristics. + </para> +</listitem> +</itemizedlist> + +<para> +This extension makes it possible to clearly and explicitly specify most aspects +of keyboard behavior on a per-key basis. It adds the notion of a numeric +keyboard group to the global keyboard state and provides mechanisms to more +closely track the logical and physical state of the keyboard. For keyboard +control clients, this extension provides descriptions and symbolic names for +many aspects of keyboard appearance and behavior. It also includes a number of +keyboard controls designed to make keyboards more accessible to people with +movement impairments. +</para> + + +<para> +The X Keyboard Extension essentially replaces the core protocol definition of a +keyboard. The following sections describe the new capabilities of the extension +and the effect of the extension on core protocol requests, events and errors. +</para> + +<sect1 id='conventions_and_assumptions'> +<title>Conventions and Assumptions</title> +<para> +This document uses the syntactic +conventions, common types, and errors defined in sections two through four of +the specification of the X Window System Protocol. This document assumes +familiarity with the fundamental concepts of X, especially those related to the +way that X handles keyboards. Readers who are not familiar with the meaning or +use of keycodes, keysyms or modifiers should consult (at least) the first five +chapters of the protocol specification of the X Window System before +continuing. +</para> +</sect1> +</chapter> |