[tklock] Do not allow tkunlock while display is blanked. Fixes MER#1831

If lockscreen blanking timeout happens while user has finished unlock
gesture but has not yet lifted the finger off screen, the gesture gets
finalized due to due to display getting powered off and lockscreen is
left in deactivated state - or in case the lpm feature is enabled, the
display can even bounce back on.

As the intent is that deactivating lockscreen should happen only as a
response to explicit user actions, there should be no need to allow such
actions to be requested when display is off and such interaction with the
user is not really possible.

Enforce this intent and do not allow tkunlock requests made while display
is not in fully powered up state.

Note that this is only protection against accidental unlocking. Applications
can still request display to be powered on. And if that is allowed, they
can also request lockscreen deactivation (which can still be denied due to
other reasons such as device lock being active).

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>

tklock.c

@@ -5863,6 +5863,57 @@ static gboolean tklock_dbus_mode_get_req_cb(DBusMessage *const msg)
     return status;
 }
 
+/** Apply allow/deny policy for TKLock requests received over D-Bus
+ *
+ * Basically locking is always allowed, but unlocking only when
+ * display already is / is making transition to powered up state.
+ *
+ * @param state requested state
+ *
+ * @returns allowed state
+ */
+static lock_state_t
+tklock_dbus_sanitize_requested_mode(lock_state_t state)
+{
+    /* Translate toggle requests to something we can evaluate */
+    if( state == LOCK_TOGGLE )
+        state = tklock_ui_enabled ? LOCK_OFF : LOCK_ON;
+
+    switch( state ) {
+    default:
+    case LOCK_UNDEF:
+    case LOCK_TOGGLE:
+        break;
+
+    case LOCK_OFF:
+    case LOCK_OFF_DELAYED:
+    case LOCK_OFF_PROXIMITY:
+        state = LOCK_OFF;
+        switch( display_state_next ) {
+        case MCE_DISPLAY_ON:
+        case MCE_DISPLAY_DIM:
+            break;
+        default:
+            if( tklock_ui_enabled ) {
+                mce_log(LL_WARN, "tkunlock denied due to display=%s",
+                        display_state_repr(display_state_next));
+                state = LOCK_ON;
+            }
+            break;
+        }
+        goto EXIT;
+
+    case LOCK_ON:
+    case LOCK_ON_DIMMED:
+    case LOCK_ON_PROXIMITY:
+    case LOCK_ON_DELAYED:
+        state = LOCK_ON;
+        break;
+    }
+EXIT:
+    return state;
+}
+
 /**
  * D-Bus callback for the tklock mode change method call
  *
@@ -5905,6 +5956,7 @@ static gboolean tklock_dbus_mode_change_req_cb(DBusMessage *const msg)
 
     if( state != LOCK_UNDEF ) {
         tklock_ui_notified = -1;
+        state = tklock_dbus_sanitize_requested_mode(state);
         tklock_datapipe_tk_lock_cb(GINT_TO_POINTER(state));
     }
 
@@ -5978,10 +6030,12 @@ static gboolean tklock_dbus_systemui_callback_cb(DBusMessage *const msg)
     mce_log(LL_DEVEL, "tklock callback value: %d, from %s", result,
             mce_dbus_get_message_sender_ident(msg));
 
+    lock_state_t state = LOCK_OFF;
     switch( result ) {
     case TKLOCK_UNLOCK:
         tklock_ui_notified = -1;
-        tklock_ui_set(false);
+        state = tklock_dbus_sanitize_requested_mode(state);
+        tklock_datapipe_tk_lock_cb(GINT_TO_POINTER(state));
         break;
 
     default: