[libcalamaresui] Expose slideshow image names for API -1

- Branding shows the slide pathnames or the slide QML, depending
  on selected API (which depends on the config-file).
- Use one slideshow or the other.

src/libcalamaresui/Branding.cpp

@@ -249,6 +249,7 @@ Branding::Branding( const QString& brandingFilePath, QObject* parent )
                 }
 
                 m_slideshowFilenames = slideShowPictures;
+                m_slideshowAPI = -1;
             }
             else if ( doc[ "slideshow" ].IsScalar() )
             {
@@ -259,12 +260,8 @@ Branding::Branding( const QString& brandingFilePath, QObject* parent )
                           QString( "Slideshow file %1 does not exist or is not a valid QML file." )
                               .arg( slideshowFi.absoluteFilePath() ) );
                 m_slideshowPath = slideshowFi.absoluteFilePath();
-            }
-            else
-            {
-                bail( m_descriptorPath, "Syntax error in slideshow sequence." );
-            }
 
+                // API choice is relevant for QML slideshow
                 int api = doc[ "slideshowAPI" ].IsScalar() ? doc[ "slideshowAPI" ].as< int >() : -1;
                 if ( ( api < 1 ) || ( api > 2 ) )
                 {
@@ -273,6 +270,11 @@ Branding::Branding( const QString& brandingFilePath, QObject* parent )
                 }
                 m_slideshowAPI = api;
             }
+            else
+            {
+                bail( m_descriptorPath, "Syntax error in slideshow sequence." );
+            }
+        }
         catch ( YAML::Exception& e )
         {
             CalamaresUtils::explainYamlException( e, ba, file.fileName() );

src/libcalamaresui/Branding.h

@@ -165,8 +165,16 @@ public:
      */
     QString translationsDirectory() const { return m_translationsPathPrefix; }
 
-    /** @brief Path to the slideshow QML file, if any. */
+    /** @brief Path to the slideshow QML file, if any. (API == 1 or 2)*/
     QString slideshowPath() const { return m_slideshowPath; }
+    /// @brief List of pathnames of slideshow images, if any. (API == -1)
+    QStringList slideshowImages() const { return m_slideshowFilenames; }
+    /** @brief Which slideshow API to use for the slideshow?
+     *
+     *  -  2    For QML-based slideshows loaded asynchronously (current)
+     *  -  1    For QML-based slideshows, loaded when shown (legacy)
+     *  - -1    For oldschool image-slideshows.
+     */
     int slideshowAPI() const { return m_slideshowAPI; }
 
     QPixmap image( Branding::ImageEntry imageEntry, const QSize& size ) const;

src/libcalamaresui/viewpages/ExecutionViewStep.cpp

@@ -41,6 +41,24 @@
 #include <QProgressBar>
 #include <QVBoxLayout>
 
+static Calamares::Slideshow*
+makeSlideshow( QWidget* parent )
+{
+    const int api = Calamares::Branding::instance()->slideshowAPI();
+    switch ( api )
+    {
+    case -1:
+        return new Calamares::SlideshowPictures( parent );
+    case 1:
+        FALLTHRU;
+    case 2:
+        return new Calamares::SlideshowQML( parent );
+    default:
+        cWarning() << "Unknown Branding slideshow API" << api;
+        return new Calamares::SlideshowPictures( parent );
+    }
+}
+
 namespace Calamares
 {
 
@@ -49,7 +67,7 @@ ExecutionViewStep::ExecutionViewStep( QObject* parent )
     , m_widget( new QWidget )
     , m_progressBar( new QProgressBar )
     , m_label( new QLabel )
-    , m_slideshow( new SlideshowQML( m_widget ) )
+    , m_slideshow( makeSlideshow( m_widget ) )
 {
     QVBoxLayout* layout = new QVBoxLayout( m_widget );
     QVBoxLayout* innerLayout = new QVBoxLayout;

src/libcalamaresui/viewpages/Slideshow.cpp

@@ -179,7 +179,7 @@ SlideshowPictures::SlideshowPictures( QWidget* parent )
     , m_label( new QLabel( parent ) )
     , m_timer( new QTimer( this ) )
     , m_imageIndex( 0 )
-    , m_images { QStringLiteral( ":/data/images/yes.svgz" ), QStringLiteral( ":/data/images/no.svgz" ) }
+    , m_images( Branding::instance()->slideshowImages() )
 {
     m_timer->setInterval( std::chrono::milliseconds( 2000 ) );
     connect( m_timer, &QTimer::timeout, this, &SlideshowPictures::next );