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diff --git a/specs/ch14.xml b/specs/ch14.xml new file mode 100644 index 0000000..98bde5d --- /dev/null +++ b/specs/ch14.xml @@ -0,0 +1,94 @@ +<chapter id='replacing_the_keyboard_on_the_fly'> +<title>Replacing the Keyboard "On-the-Fly"</title> + +<para> +XKB supports the <emphasis> +XkbNewKeyboardNotify</emphasis> + event, which reports a change in keyboard geometry or the range of supported +keycodes. The server can generate an <emphasis> +XkbNewKeyboardNotify</emphasis> + event when it detects a new keyboard, or in response to an <emphasis> +XkbGetKeyboardByName</emphasis> + request (see <ulink url="XKBproto.htm#50332257_13490">See Using the Server’s +Database of Keyboard Components</ulink>) which loads a new keyboard description. +</para> + + +<para> +When a client opens a connection to the X server, the server reports the +minimum and maximum keycodes. If the range of supported keycodes is changed, +XKB keeps track of the minimum and maximum keycodes that were reported to each +client and filters out any events that fall outside of that range. Note that +these events are simply ignored; they are not delivered to some other client. +</para> + + +<para> +When the server sends an <emphasis> +XkbNewKeyboardNotify</emphasis> + event to a client to inform it of the new keycode range, XKB resets the stored +range of legal keycodes to the keycode range reported in the event. Non-XKB +clients and XKB-aware clients that do not request <emphasis> +XkbNewKeyboardNotify</emphasis> + events never receive events from keys that fall outside of the legal range +that XKB maintains for that client. +</para> + + +<para> +When a client requests <emphasis> +XkbNewKeyboardNotify</emphasis> + events, the server compares the range of keycodes for the current keyboard to +the range of keycodes that are valid for the client. If they are not the same, +the server immediately sends that client an <emphasis> +XkbNewKeyboardNotify</emphasis> + event. Even if the "new" keyboard is not new to the server, it is new to this +particular client. +</para> + + +<para> +In addition to filtering out-of-range key events, XKB: +</para> + +<itemizedlist> +<listitem> + <para>Adjusts core protocol <emphasis> +MappingNotify</emphasis> + events to refer only to keys that match the stored legal range. + </para> +</listitem> +<listitem> + <para>Reports keyboard mappings for keys that match the stored legal range to +clients that issue a core protocol <emphasis> +GetKeyboardMapping</emphasis> + request. + </para> +</listitem> +<listitem> + <para>Reports modifier mappings only for keys that match the stored legal +range to clients that issue a core protocol <emphasis> +GetModifierMapping</emphasis> + request. + </para> +</listitem> +<listitem> + <para>Restricts the core protocol <emphasis> +ChangeKeyboardMapping</emphasis> + and <emphasis> +SetModifierMapping</emphasis> + requests to keys that fall inside the stored legal range. + </para> +</listitem> +</itemizedlist> + +<para> +In short, XKB does everything possible to hide the fact that the range of legal +keycodes has changed from clients non-XKB clients, which cannot be expected to +deal with it. The corresponding XKB events and requests do <emphasis> +not</emphasis> + pay attention to the legal keycode range in the same way because XKB makes it +possible for clients to track changes to the keycode range for a device and +respond to them. +</para> +</chapter> |