[libcalamaresui] activate -> change state

- since we also need to *disable* the shortcuts, and should tell a
   V1 slideshow that it no longer is running,
 - use existing function to set the property to true / false depending.
 - instead of changeState( true ) or changeStage( false ), use
   meaningful enum names so that the code at the call site
   becomes readable; make the boolean part internal to the
   state-changing method.

src/libcalamaresui/ExecutionViewStep.cpp

@@ -179,28 +179,53 @@ ExecutionViewStep::loadQmlV2()
     }
 }
 
-static void
+/// @brief State-change of the slideshow, for changeSlideShowState()
-activateSlideShow( QQuickItem* slideshow, QQuickWidget* widget)
+enum class Slideshow
 {
+    Start,
+    Stop
+};
+
+/** @brief Tells the slideshow we activated or left the show.
+ *
+ * If @p state is @c Slideshow::Start, calls suitable activation procedures.
+ * If @p state is @c Slideshow::Stop, calls deactivation procedures.
+ *
+ * Applies V1 and V2 QML activation / deactivation:
+ *  - V1 loads the QML in @p widget on activation. Sets root object property
+ *    *activatedInCalamares* as appropriate.
+ *  - V2 calls onActivate() or onLeave() in the QML as appropriate. Also
+ *    sets the *activatedInCalamares* property.
+ */
+static void
+changeSlideShowState( Slideshow state, QQuickItem* slideshow, QQuickWidget* widget )
+{
+    bool activate = state == Slideshow::Start;
+
     if ( Branding::instance()->slideshowAPI() == 2 )
     {
         // The QML was already loaded in the constructor, need to start it
-        callQMLFunction( slideshow, "onActivate" );
+        callQMLFunction( slideshow, activate ? "onActivate" : "onLeave" );
     }
     else if ( !Calamares::Branding::instance()->slideshowPath().isEmpty() )
     {
         // API version 1 assumes onCompleted is the trigger
+        if ( activate )
+        {
             widget->setSource( QUrl::fromLocalFile( Calamares::Branding::instance()->slideshowPath() ) );
+        }
+        // needs the root object for property setting, below
         slideshow = widget->rootObject();
     }
 
+    // V1 API has picked up the root object for use, V2 passed it in.
     if ( slideshow )
     {
         static const char propertyName[] = "activatedInCalamares";
-        auto active = slideshow->property( propertyName );
+        auto property = slideshow->property( propertyName );
-        if ( active.isValid() && ( active.type() == QVariant::Bool ) && !active.toBool() )
+        if ( property.isValid() && ( property.type() == QVariant::Bool ) && ( property.toBool() != activate ) )
         {
-            slideshow->setProperty( propertyName, true );
+            slideshow->setProperty( propertyName, activate );
         }
     }
 }
@@ -234,7 +259,7 @@ ExecutionViewStep::loadQmlV2Complete()
             {
                 // We're alreay visible! Must have been slow QML loading, and we
                 // passed onActivate already.
-                activateSlideShow( m_qmlObject, m_qmlShow );
+                changeSlideShowState( Slideshow::Start, m_qmlObject, m_qmlShow );
             }
         }
     }
@@ -243,7 +268,7 @@ ExecutionViewStep::loadQmlV2Complete()
 void
 ExecutionViewStep::onActivate()
 {
-    activateSlideShow( m_qmlObject, m_qmlShow );
+    changeSlideShowState( Slideshow::Start, m_qmlObject, m_qmlShow );
 
     JobQueue* queue = JobQueue::instance();
     foreach ( const QString& instanceKey, m_jobInstanceKeys )
@@ -291,10 +316,10 @@ ExecutionViewStep::updateFromJobQueue( qreal percent, const QString& message )
 void
 ExecutionViewStep::onLeave()
 {
+    changeSlideShowState( Slideshow::Stop, m_qmlObject, m_qmlShow );
     // API version 2 is explicitly stopped; version 1 keeps running
     if ( Branding::instance()->slideshowAPI() == 2 )
     {
-        callQMLFunction( m_qmlObject, "onLeave" );
         delete m_qmlObject;
         m_qmlObject = nullptr;
     }