<chapter id='Xkb_Events'> <title>Xkb Events</title> <para> The primary way the X server communicates with clients is by sending X events to them. Some events are sent to all clients, while others are sent only to clients that have requested them. Some of the events that can be requested are associated with a particular window and are only sent to those clients who have both requested the event and specified the window in which the event occurred. </para> <para> The Xkb extension uses events to communicate the keyboard status to interested clients. These events are not associated with a particular window. Instead, all Xkb keyboard status events are reported to all interested clients, regardless of which window currently has the keyboard focus and regardless of the grab state of the keyboard.<footnote><para>The one exception to this rule is the XkbExtensionDeviceNotify event report that is sent when a client attempts to use an unsupported feature of an X Input Extension device (see section 21.4). </para></footnote> <!-- xref --> </para> <para> The X server reports the events defined by the Xkb extension to your client application only if you have requested them. You may request Xkb events by calling either <emphasis> XkbSelectEvents</emphasis> or <emphasis> XkbSelectEventDetails</emphasis> . <emphasis> XkbSelectEvents</emphasis> requests Xkb events by their event type and causes them to be reported to your client application under all circumstances. You can specify a finer granularity for event reporting by using <emphasis> XkbSelectEventDetails</emphasis> ; in this case events are reported only when the specific detail conditions you specify have been met. </para> <sect1 id='Xkb_Event_Types'> <title>Xkb Event Types</title> <para> The Xkb Extension adds new event types to the X protocol definition. An Xkb event type is defined by two fields in the X event data structure. One is the <emphasis> type</emphasis> field, containing the <emphasis> base event code.</emphasis> This base event code is a value the X server assigns to each X extension at runtime and thatidentifies the extension that generated the event; thus, the event code in the <emphasis> type</emphasis> field identifies the event as an Xkb extension event, rather than an event from another extension or a core X protocol event. You can obtain the base event code via a call to <emphasis> XkbQueryExtension</emphasis> or <emphasis> XkbOpenDisplay</emphasis> . The second field is the Xkb event type, which contains a value uniquely identifying each different Xkb event type. Possible values are defined by constants declared in the header file <X11/extensions/Xkb.h>. </para> <para> Table 4.1 lists the categories of events defined by Xkb and their associated event types, as defined in <emphasis> Xkb.h</emphasis> . Each event is described in more detail in the section referenced for that event. </para> <table frame='topbot'> <title>Xkb Event Types</title> <?dbfo keep-together="always" ?> <tgroup cols='4' align='left' colsep='0' rowsep='0'> <colspec colname='c1' colwidth='3.0*'/> <colspec colname='c2' colwidth='4.0*'/> <colspec colname='c3' colwidth='1.0*'/> <colspec colname='c4' colwidth='1.0*'/> <thead> <row rowsep='1'> <entry>Event Type</entry> <entry>Conditions Generating Event</entry> <entry>Section</entry> <entry>Page</entry> </row> </thead> <tbody> <row> <entry> <para><emphasis>XkbNewKeyboardNotify</emphasis></para> </entry> <entry> <para>Keyboard geometry; keycode range change</para> </entry> <entry> <para>19</para> </entry> <entry> <para>187</para> </entry> </row> <row> <entry> <para> <emphasis>XkbMapNotify</emphasis> </para> </entry> <entry> <para>Keyboard mapping change</para> </entry> <entry> <para>14.4</para> </entry> <entry> <para>122</para> </entry> </row> <row> <entry> <para><emphasis>XkbStateNotify</emphasis></para> </entry> <entry> <para>Keyboard state change</para> </entry> <entry> <para>5.4</para> </entry> <entry> <para>25</para> </entry> </row> <row> <entry> <para><emphasis>XkbControlsNotify</emphasis></para> </entry> <entry> <para>Keyboard controls state change</para> </entry> <entry> <para>10.11</para> </entry> <entry> <para>79</para> </entry> </row> <row> <entry> <para><emphasis>XkbIndicatorStateNotify</emphasis></para> </entry> <entry> <para>Keyboard indicators state change</para> </entry> <entry> <para>8.5</para> </entry> <entry> <para>45</para> </entry> </row> <row> <entry> <para><emphasis>XkbIndicatorMapNotify</emphasis></para> </entry> <entry> <para>Keyboard indicators map change</para> </entry> <entry> <para>8.5</para> </entry> <entry> <para>45</para> </entry> </row> <row> <entry> <para><emphasis>XkbNamesNotify</emphasis></para> </entry> <entry> <para>Keyboard name change</para> </entry> <entry> <para>18.5</para> </entry> <entry> <para>185</para> </entry> </row> <row> <entry> <para><emphasis>XkbCompatMapNotify</emphasis></para> </entry> <entry> <para>Keyboard compatibility map change</para> </entry> <entry> <para>17.5</para> </entry> <entry> <para>178</para> </entry> </row> <row> <entry> <para><emphasis>XkbBellNotify</emphasis></para> </entry> <entry> <para>Keyboard bell generated</para> </entry> <entry> <para>9.4</para> </entry> <entry> <para>52</para> </entry> </row> <row> <entry> <para><emphasis>XkbActionMessage</emphasis></para> </entry> <entry> <para>Keyboard action message</para> </entry> <entry> <para>16.1.11</para> </entry> <entry> <para>155</para> </entry> </row> <row> <entry> <para><emphasis>XkbAccessXNotify</emphasis></para> </entry> <entry> <para>AccessX state change</para> </entry> <entry> <para>10.6.4</para> </entry> <entry> <para>65</para> </entry> </row> <row> <entry> <para><emphasis>XkbExtensionDeviceNotify</emphasis></para> </entry> <entry> <para>Extension device change</para> </entry> <entry> <para>21.6</para> </entry> <entry> <para>207</para> </entry> </row> </tbody> </tgroup> </table> </sect1> <sect1 id='Xkb_Event_Data_Structures'> <title>Xkb Event Data Structures</title> <para> Xkb reports each event it generates in a unique structure holding the data values needed to describe the conditions the event is reporting. However, all Xkb events have certain things in common. These common features are contained in the same fields at the beginning of all Xkb event structures and are described in the <emphasis> XkbAnyEvent</emphasis> structure: </para> <para><programlisting> typedef struct { int type; /* Xkb extension base event code */ unsigned long serial; /* X server serial number for event */ Bool send_event; /* <emphasis> True</emphasis> => synthetically generated */ Display * display; /* server connection where event generated */ Time time; /* server time when event generated */ int xkb_type; /* Xkb minor event code */ unsigned int device; /* Xkb device ID, will not be <emphasis>XkbUseCoreKbd</emphasis> */ } <emphasis>XkbAnyEvent</emphasis> ; </programlisting></para> <para> For any Xkb event, the <emphasis> type</emphasis> field is set to the base event code for the Xkb extension, assigned by the server to all Xkb extension events. The <emphasis> serial</emphasis> , <emphasis> send_event</emphasis> , and <emphasis> display</emphasis> fields are as described for all X11 events. The <emphasis> time</emphasis> field is set to the time when the event was generated and is expressed in milliseconds. The <emphasis> xkb_type</emphasis> field contains the minor extension event code, which is the extension event type, and is one of the values listed in Table 4.1. The <emphasis> device</emphasis> field contains the keyboard device identifier associated with the event. This is never <emphasis> XkbUseCoreKbd</emphasis> , even if the request that generated the event specified a device of <emphasis> XkbUseCoreKbd</emphasis> . If the request that generated the event specified <emphasis> XkbUseCoreKbd</emphasis> , <emphasis> device</emphasis> contains a value assigned by the server to specify the core keyboard. If the request that generated the event specified an X input extension device, <emphasis> device</emphasis> contains that same identifier. </para> <para> Other data fields specific to individual Xkb events are described in subsequent chapters where the events are described. </para> </sect1> <sect1 id='Selecting_Xkb_Events'> <title>Selecting Xkb Events</title> <para> Xkb events are selected using an event mask, much the same as normal core X events are selected. However, unlike selecting core X events, where you must specify the selection status (on or off) for all possible event types whenever you wish to change the selection criteria for any one event, Xkb allows you to restrict the specification to only the event types you wish to change. This means that you do not need to remember the event selection values for all possible types each time you want to change one of them. </para> <para> Many Xkb event types are generated under several different circumstances. When selecting to receive an Xkb event, you may specify either that you want it delivered under all circumstances, or that you want it delivered only for a subset of the possible circumstances. </para> <para> You can also deselect an event type that was previously selected for, using the same granularity. </para> <para> Xkb provides two functions to select and deselect delivery of Xkb events. <emphasis> XkbSelectEvents</emphasis> allows you to select or deselect delivery of more than one Xkb event type at once. Events selected using <emphasis> XkbSelectEvents</emphasis> are delivered to your program under all circumstances that generate the events. To restrict delivery of an event to a subset of the conditions under which it occurs, use <emphasis> XkbSelectEventDetails</emphasis> . <emphasis> XkbSelectEventDetails</emphasis> only allows you to change the selection conditions for a single event at a time, but it provides a means of fine-tuning the conditions under which the event is delivered. </para> <para> To select and / or deselect for delivery of one or more Xkb events and have them delivered under all conditions, use <emphasis> XkbSelectEvents</emphasis> . </para> <informaltable frame='none'> <?dbfo keep-together="always" ?> <tgroup cols='1' align='left' colsep='0' rowsep='0'> <colspec colname='c1' colwidth='1.0*'/> <tbody> <row> <entry role='functiondecl'> Bool <emphasis> XkbSelectEvents</emphasis> (<emphasis> display, device_spec, bits_to_change, values_for_bits</emphasis> ) </entry> </row> <row> <entry role='functionargdecl'> Display * <emphasis> display</emphasis> ; /* connection to the X server */ </entry> </row> <row> <entry role='functionargdecl'> unsigned int <emphasis> device_spec</emphasis> ; /* device ID, or <emphasis> XkbUseCoreKbd</emphasis> */ </entry> </row> <row> <entry role='functionargdecl'> unsigned long int <emphasis> bits_to_change; </emphasis> /* determines events to be selected / deselected */ </entry> </row> <row> <entry role='functionargdecl'> unsigned long int <emphasis> values_for_bits</emphasis> ; /* 1=>select, 0->deselect; for events in <emphasis> bits_to_change</emphasis> */ </entry> </row> </tbody> </tgroup> </informaltable> <para> This request changes the Xkb event selection mask for the keyboard specified by <emphasis> device_spec</emphasis> . </para> <para> Each Xkb event that can be selected is represented by a bit in the <emphasis> bits_to_change</emphasis> and <emphasis> values_for_bits</emphasis> masks. Only the event selection bits specified by the <emphasis> bits_to_change</emphasis> parameter are affected; any unspecified bits are left unchanged. To turn on event selection for an event, set the bit for the event in the <emphasis> bits_to_change</emphasis> parameter and set the corresponding bit in the <emphasis> values_for_bits</emphasis> parameter. To turn off event selection for an event, set the bit for the event in the <emphasis> bits_to_change</emphasis> parameter and do not set the corresponding bit in the <emphasis> values_for_bits</emphasis> parameter. The valid values for both of these parameters are an inclusive bitwise OR of the masks shown in Table 4.2. There is no interface to return your client’s current event selection mask. Clients cannot set other clients’ event selection masks. </para> <para> If a bit is not set in the <emphasis> bits_to_change</emphasis> parameter, but the corresponding bit is set in the <emphasis> values_for_bits</emphasis> parameter, a <emphasis> BadMatch</emphasis> protocol error results. If an undefined bit is set in either the <emphasis> bits_to_change</emphasis> or the <emphasis> values_for_bits</emphasis> parameter, a <emphasis> BadValue</emphasis> protocol error results. </para> <para> All event selection bits are initially zero for clients using the Xkb extension. Once you set some bits, they remain set for your client until you clear them via another call to <emphasis> XkbSelectEvents</emphasis> . </para> <para> <emphasis> XkbSelectEvents</emphasis> returns <emphasis> False</emphasis> if the Xkb extension has not been initilialized and <emphasis> True</emphasis> otherwise. </para> <para> To select or deselect for a specific Xkb event and optionally place conditions on when events of that type are reported to your client, use <emphasis> XkbSelectEventDetails</emphasis> . This allows you to exercise a finer granularity of control over delivery of Xkb events with <emphasis> XkbSelectEvents</emphasis> . </para> <informaltable frame='none'> <?dbfo keep-together="always" ?> <tgroup cols='1' align='left' colsep='0' rowsep='0'> <colspec colname='c1' colwidth='1.0*'/> <tbody> <row> <entry role='functiondecl'> Bool <emphasis> XkbSelectEventDetails</emphasis> (<emphasis> display, device_spec, event_type, bits_to_change</emphasis> , <emphasis> values_for_bits</emphasis> ) </entry> </row> <row> <entry role='functionargdecl'> Display * <emphasis> display</emphasis> ; /* connection to the X server */ </entry> </row> <row> <entry role='functionargdecl'> unsigned int <emphasis> device_spec</emphasis> ; /* device ID, or <emphasis> XkbUseCoreKbd</emphasis> */ </entry> </row> <row> <entry role='functionargdecl'> unsigned int <emphasis> event_type</emphasis> ; /* Xkb event type of interest */ </entry> </row> <row> <entry role='functionargdecl'> unsigned long int <emphasis> bits_to_change</emphasis> ; /* event selection details */ </entry> </row> <row> <entry role='functionargdecl'> unsigned long int <emphasis> values_for_bits</emphasis> ; /* values for bits selected by <emphasis> bits_to_change</emphasis> */ </entry> </row> </tbody> </tgroup> </informaltable> <para> While <emphasis> XkbSelectEvents</emphasis> allows multiple events to be selected, <emphasis> XkbSelectEventDetails</emphasis> changes the selection criteria for a single type of Xkb event. The interpretation of the <emphasis> bits_to_change</emphasis> and <emphasis> values_for_bits</emphasis> masks depends on the event type in question. </para> <para> <emphasis> XkbSelectEventDetails</emphasis> changes the Xkb event selection mask for the keyboard specified by <emphasis> device_spec</emphasis> and the Xkb event specified by <emphasis> event_type</emphasis> . To turn on event selection for an event detail, set the bit for the detail in the <emphasis> bits_to_change</emphasis> parameter and set the corresponding bit in the <emphasis> values_for_bits</emphasis> parameter. To turn off event detail selection for a detail, set the bit for the detail in the <emphasis> bits_to_change</emphasis> parameter and do not set the corresponding bit in the <emphasis> values_for_bits</emphasis> parameter. </para> <para> If an invalid event type is specified, a <emphasis> BadValue</emphasis> protocol error results. If a bit is not set in the <emphasis> bits_to_change</emphasis> parameter, but the corresponding bit is set in the <emphasis> values_for_bits</emphasis> parameter, a <emphasis> BadMatch</emphasis> protocol error results. If an undefined bit is set in either the <emphasis> bits_to_change</emphasis> or the <emphasis> values_for_bits</emphasis> parameter, a <emphasis> BadValue</emphasis> protocol error results. </para> <para> For each type of Xkb event, the legal event details that you can specify in the <emphasis> XkbSelectEventDetails</emphasis> request are listed in the chapters that describe each event in detail. </para> <sect2 id='Event_Masks'> <title>Event Masks</title> <para> The X server reports the events defined by Xkb to your client application only if you have requested them via a call to <emphasis> XkbSelectEvents</emphasis> or <emphasis> XkbSelectEventDetails</emphasis> . Specify the event types in which you are interested in a mask, as described in section 4.3. </para> <para> Table 4.2 lists the event mask constants that can be specified with the <!-- xref --> <emphasis> XkbSelectEvents</emphasis> request and the circumstances in which the mask should be specified. </para> <table frame='topbot'> <title>XkbSelectEvents Mask Constants</title> <?dbfo keep-together="always" ?> <tgroup cols='3' align='left' colsep='0' rowsep='0'> <colspec colname='c1' colwidth='2.0*'/> <colspec colname='c2' colwidth='1.0*'/> <colspec colname='c3' colwidth='2.0*'/> <thead> <row rowsep='1'> <entry>Event Mask</entry> <entry>Value</entry> <entry>Notification Wanted</entry> </row> </thead> <tbody> <row> <entry> <emphasis>XkbNewKeyboardNotifyMask</emphasis> </entry> <entry>(1L<<0)</entry> <entry>Keyboard geometry change</entry> </row> <row> <entry> <emphasis>XkbMapNotifyMask</emphasis> </entry> <entry>(1L<<1)</entry> <entry>Keyboard mapping change</entry> </row> <row> <entry> <para><emphasis>XkbStateNotifyMask</emphasis></para> </entry> <entry>(1L<<2)</entry> <entry><para>Keyboard state change</para></entry> </row> <row> <entry> <para><emphasis>XkbControlsNotifyMask</emphasis></para> </entry> <entry>(1L<<3)</entry> <entry>Keyboard control change</entry> </row> <row> <entry> <emphasis>XkbIndicatorStateNotifyMask</emphasis> </entry> <entry>(1L<<4)</entry> <entry>Keyboard indicator state change</entry> </row> <row> <entry> <emphasis>XkbIndicatorMapNotifyMask</emphasis> </entry> <entry>(1L<<5)</entry> <entry>Keyboard indicator map change</entry> </row> <row> <entry> <emphasis>XkbNamesNotifyMask</emphasis> </entry> <entry>(1L<<6)</entry> <entry>Keyboard name change</entry> </row> <row> <entry> <emphasis>XkbCompatMapNotifyMask</emphasis> </entry> <entry>(1L<<7)</entry> <entry>Keyboard compat map change</entry> </row> <row> <entry> <emphasis>XkbBellNotifyMask</emphasis> </entry> <entry>(1L<<8)</entry> <entry>Bell</entry> </row> <row> <entry> <emphasis>XkbActionMessageMask</emphasis> </entry> <entry>(1L<<9)</entry> <entry>Action message</entry> </row> <row> <entry> <emphasis>XkbAccessXNotifyMask</emphasis> </entry> <entry>(1L<<10)</entry> <entry>AccessX features</entry> </row> <row> <entry> <emphasis>XkbExtensionDeviceNotifyMask</emphasis> </entry> <entry>(1L<<11)</entry> <entry>Extension device</entry> </row> <row> <entry> <emphasis>XkbAllEventsMask</emphasis> </entry> <entry>(0xFFF)</entry> <entry>All Xkb events</entry> </row> </tbody> </tgroup> </table> </sect2> </sect1> <sect1 id='Unified_Xkb_Event_Type'> <title>Unified Xkb Event Type</title> <para> The <emphasis> XkbEvent</emphasis> structure is a union of the individual structures declared for each Xkb event type and for the core protocol <emphasis> XEvent</emphasis> type. Given an <emphasis> XkbEvent</emphasis> structure, you may use the <emphasis> type</emphasis> field to determine if the event is an Xkb event (<emphasis> type</emphasis> equals the Xkb base event code; see section 2.4). If the event is an Xkb event, you may then use the <emphasis> any.xkb_type</emphasis> field to determine the type of Xkb event and thereafter access the event-dependent components using the union member corresponding to the particular Xkb event type. </para> <para><programlisting> typedef union _XkbEvent { int type; XkbAnyEvent any; XkbStateNotifyEvent state; XkbMapNotifyEvent map; XkbControlsNotifyEvent ctrls; XkbIndicatorNotifyEvent indicators; XkbBellNotifyEvent bell; XkbAccessXNotifyEvent accessx; XkbNamesNotifyEvent names; XkbCompatMapNotifyEvent compat; XkbActionMessageEvent message; XkbExtensionDeviceNotifyEvent device; XkbNewKeyboardNotifyEvent new_kbd; XEvent core; } <emphasis>XkbEvent</emphasis>; </programlisting></para> <para> This unified Xkb event type includes a normal <emphasis> XEvent</emphasis> as used by the core protocol, so it is straightforward for applications that use Xkb events to call the X library event functions without having to cast every reference. For example, to get the next event, you can simply declare a variable of type <emphasis> XkbEvent</emphasis> and call: </para> <para>XNextEvent(dpy,&xkbev.core);</para> </sect1> </chapter>