xorg-server-1.18.4-xkb-switch-on-release.patch

--- xkb/xkbActions.c.orig	2016-07-19 20:07:29.000000000 +0300
+++ xkb/xkbActions.c	2016-09-24 03:39:42.766614063 +0300
@@ -351,26 +351,82 @@ _XkbFilterLatchState(XkbSrvInfoPtr xkbi,
     return 1;
 }
 
+static int xkbSwitchGroupOnRelease(void)
+{
+    /* TODO: user configuring */
+    return TRUE;
+}
+
+static void xkbUpdateLockedGroup(XkbSrvInfoPtr xkbi, XkbAction* pAction)
+{
+    XkbGroupAction ga = pAction->group;
+    if (ga.flags&XkbSA_GroupAbsolute)
+        xkbi->state.locked_group= XkbSAGroup(&ga);
+    else
+        xkbi->state.locked_group+= XkbSAGroup(&ga);
+}
+
+static XkbFilterPtr _XkbNextFreeFilter(XkbSrvInfoPtr xkbi);
+
 static int
-_XkbFilterLockState(XkbSrvInfoPtr xkbi,
+_XkbFilterLockGroup(XkbSrvInfoPtr xkbi,
                     XkbFilterPtr filter, unsigned keycode, XkbAction *pAction)
 {
-    if (filter->keycode == 0) /* initial press */
+    int sendEvent = 1;
+
+    if (!xkbSwitchGroupOnRelease()) {
+        xkbUpdateLockedGroup(xkbi, pAction);
+        return sendEvent;
+    }
+    
+    /* Delay switch till button release */
+    if (filter->keycode==0) {                /* initial press */
         AccessXCancelRepeatKey(xkbi, keycode);
+        filter->keycode = keycode;
+        filter->active = 1;
+        filter->filterOthers = 0; /* for what? */
+        filter->filter = _XkbFilterLockGroup;
 
-    if (pAction && (pAction->type == XkbSA_LockGroup)) {
-        if (pAction->group.flags & XkbSA_GroupAbsolute)
-            xkbi->state.locked_group = XkbSAGroup(&pAction->group);
-        else
-            xkbi->state.locked_group += XkbSAGroup(&pAction->group);
-        return 1;
+        /* filter->priv = 0; */
+        filter->upAction = *pAction;
+
+        /* Ok, now we need to simulate the action which would go if this action didn't block it.
+           XkbSA_SetMods is the one: it is to set modifier' flag up. */
+        {
+            XkbStateRec        fake_state = xkbi->state;
+            XkbAction act;
+
+            fake_state.mods = 0;
+            act = XkbGetKeyAction(xkbi, &fake_state, keycode);
+
+            /* KLUDGE: XkbSA_SetMods only? */
+            if (act.type == XkbSA_SetMods) { 
+                XkbFilterPtr filter = _XkbNextFreeFilter(xkbi);
+                sendEvent = _XkbFilterSetState(xkbi,filter,keycode,&act);
+            }
+        }
+    }
+    else {
+          /* do nothing if some button else is pressed */
+        if (!pAction)
+            xkbUpdateLockedGroup(xkbi, &filter->upAction);
+        filter->active = 0;
     }
+
+    return sendEvent;
+}
+
+static int
+_XkbFilterLockMods(XkbSrvInfoPtr xkbi,
+                    XkbFilterPtr filter, unsigned keycode, XkbAction *pAction)
+{
     if (filter->keycode == 0) { /* initial press */
+        AccessXCancelRepeatKey(xkbi, keycode);
         filter->keycode = keycode;
         filter->active = 1;
         filter->filterOthers = 0;
         filter->priv = xkbi->state.locked_mods & pAction->mods.mask;
-        filter->filter = _XkbFilterLockState;
+        filter->filter = _XkbFilterLockMods;
         filter->upAction = *pAction;
         if (!(filter->upAction.mods.flags & XkbSA_LockNoLock))
             xkbi->state.locked_mods |= pAction->mods.mask;
@@ -1250,9 +1306,12 @@ XkbHandleActions(DeviceIntPtr dev, Devic
                 sendEvent = _XkbFilterLatchState(xkbi, filter, key, &act);
                 break;
             case XkbSA_LockMods:
+                filter = _XkbNextFreeFilter(xkbi);
+                sendEvent = _XkbFilterLockMods(xkbi,filter,key,&act);
+                break;
             case XkbSA_LockGroup:
                 filter = _XkbNextFreeFilter(xkbi);
-                sendEvent = _XkbFilterLockState(xkbi, filter, key, &act);
+                sendEvent = _XkbFilterLockGroup(xkbi, filter, key, &act);
                 break;
             case XkbSA_ISOLock:
                 filter = _XkbNextFreeFilter(xkbi);