engine: fix wrong channel offset on autodetection

debian/changelog

@@ -2,6 +2,7 @@ qlcplus (4.12.1) stable; urgency=low
 
   * engine/RGBMatrix: fix crash when a fixture group has out of bounds heads
   * engine/EFX: fix crash when previewing a cloned EFX
+  * Simple Desk: fix wrong channel offset
   * Virtual Console/Slider: fix Click & Go not applied to channels
   * Virtual Console/Frame: fix geometry after move in collapsed state
   * New fixture: American DJ FREQ Matrix Quad (thanks to Rasmus Ahlberg)

engine/src/fadechannel.cpp

@@ -102,14 +102,18 @@ void FadeChannel::unsetTypeFlag(int flag)
 
 void FadeChannel::autoDetect(const Doc *doc)
 {
+    bool fixtureWasInvalid = false;
     // reset before autodetecting
     setType(0);
 
     /* on invalid fixture, channel number is most likely
      * absolute (SimpleDesk/CueStack do it this way), so attempt
      * a reverse lookup to try and find the Fixture ID */
     if (m_fixture == Fixture::invalidId())
+    {
+        fixtureWasInvalid = true;
         m_fixture = doc->fixtureForAddress(channel());
+    }
 
     Fixture *fixture = doc->fixture(m_fixture);
     if (fixture == NULL)
@@ -123,7 +127,9 @@ void FadeChannel::autoDetect(const Doc *doc)
         m_universe = fixture->universe();
         m_address = fixture->address();
 
-        if (m_channel >= fixture->channels())
+        // if the fixture was invalid at the beginning of this method
+        // it means channel was an absolute address, so, fix it
+        if (fixtureWasInvalid)
             m_channel -= fixture->address();
 
         const QLCChannel *channel = fixture->channel(m_channel);