Input: Add focus-in event source

Add a new event source type for keypress events synthesised from focus
notifications (e.g. KeymapNotify from the parent server, when running
nested). This is used to keep the keys-down array in sync with the host
server's, without sending actual keypress events to clients.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

Xi/exevents.c

@@ -1760,6 +1760,10 @@ ProcessDeviceEvent(InternalEvent *ev, DeviceIntPtr device)
 
     switch (event->type) {
     case ET_KeyPress:
+        /* Don't deliver focus events (e.g. from KeymapNotify when running
+         * nested) to clients. */
+        if (event->source_type == EVENT_SOURCE_FOCUS)
+            return;
         if (!grab && CheckDeviceGrabs(device, event, 0))
             return;
         break;

dix/getevents.c

@@ -1101,6 +1101,11 @@ GetKeyboardEvents(InternalEvent *events, DeviceIntPtr pDev, int type,
     }
 #endif
 
+    if (type == KeymapNotify) {
+        source_type = EVENT_SOURCE_FOCUS;
+        type = KeyPress;
+    }
+
     /* refuse events from disabled devices */
     if (!pDev->enabled)
         return 0;

include/eventstr.h

@@ -83,6 +83,7 @@ enum EventType {
  */
 enum DeviceEventSource {
   EVENT_SOURCE_NORMAL = 0, /**< Default: from a user action (e.g. key press) */
+  EVENT_SOURCE_FOCUS, /**< Keys or buttons previously down on focus-in */
 };
 
 /**

xkb/xkbActions.c

@@ -1206,6 +1206,32 @@ XkbActionGetFilter(DeviceIntPtr dev, DeviceEvent *event, KeyCode key,
     XkbSrvInfoPtr xkbi = dev->key->xkbInfo;
     XkbFilterPtr filter;
 
+    /* For focus events, we only want to run actions which update our state to
+     * (hopefully vaguely kinda) match that of the host server, rather than
+     * actually execute anything. For example, if we enter our VT with
+     * Ctrl+Alt+Backspace held down, we don't want to terminate our server
+     * immediately, but we _do_ want Ctrl+Alt to be latched down, so if
+     * Backspace is released and then pressed again, the server will terminate.
+     *
+     * This is pretty flaky, and we should in fact inherit the complete state
+     * from the host server. There are some state combinations that we cannot
+     * express by running the state machine over every key, e.g. if AltGr+Shift
+     * generates a different state to Shift+AltGr. */
+    if (event->source_type == EVENT_SOURCE_FOCUS) {
+        switch (act->type) {
+        case XkbSA_SetMods:
+        case XkbSA_SetGroup:
+        case XkbSA_LatchMods:
+        case XkbSA_LatchGroup:
+        case XkbSA_LockMods:
+        case XkbSA_LockGroup:
+            break;
+        default:
+            *sendEvent = 1;
+            return;
+        }
+    }
+
     switch (act->type) {
     case XkbSA_SetMods:
     case XkbSA_SetGroup: