QskStackBox::transientindex introduced

src/layouts/QskStackBox.cpp

@@ -168,6 +168,17 @@ void QskStackBox::setCurrentIndex( int index )
     Q_EMIT currentIndexChanged( m_data->currentIndex );
 }
 
+qreal QskStackBox::transientIndex() const
+{
+    if ( auto animator = m_data->animator )
+    {
+        if ( animator->isRunning() )
+            return animator->transientIndex();
+    }
+
+    return currentIndex();
+}
+
 void QskStackBox::setCurrentItem( const QQuickItem* item )
 {
     setCurrentIndex( indexOf( item ) );

src/layouts/QskStackBox.h

@@ -17,6 +17,9 @@ class QSK_EXPORT QskStackBox : public QskIndexedLayoutBox
     Q_PROPERTY( int currentIndex READ currentIndex
         WRITE setCurrentIndex NOTIFY currentIndexChanged )
 
+    Q_PROPERTY( qreal transientIndex READ transientIndex
+        NOTIFY transientIndexChanged )
+
     Q_PROPERTY( QQuickItem* currentItem READ currentItem
         WRITE setCurrentItem NOTIFY currentItemChanged )
 
@@ -46,6 +49,8 @@ class QSK_EXPORT QskStackBox : public QskIndexedLayoutBox
     QQuickItem* currentItem() const;
     int currentIndex() const;
 
+    qreal transientIndex() const;
+
     void setDefaultAlignment( Qt::Alignment );
     Qt::Alignment defaultAlignment() const;
 
@@ -67,6 +72,7 @@ class QSK_EXPORT QskStackBox : public QskIndexedLayoutBox
 
   Q_SIGNALS:
     void currentIndexChanged( int index );
+    void transientIndexChanged( qreal index );
     void currentItemChanged( QQuickItem* );
 
   protected:

src/layouts/QskStackBoxAnimator.cpp

@@ -7,6 +7,7 @@
 #include "QskStackBox.h"
 #include "QskEvent.h"
 #include "QskQuick.h"
+#include "QskFunctions.h"
 
 static Qsk::Direction qskDirection(
     Qt::Orientation orientation, int from, int to, int itemCount )
@@ -68,7 +69,7 @@ QskStackBoxAnimator::~QskStackBoxAnimator()
 
 void QskStackBoxAnimator::setStartIndex( int index )
 {
-    m_startIndex = index;
+    m_transientIndex = m_startIndex = index;
 }
 
 void QskStackBoxAnimator::setEndIndex( int index )
@@ -97,6 +98,53 @@ QQuickItem* QskStackBoxAnimator::itemAt( int index ) const
         ( index == 0 ) ? m_startIndex : m_endIndex );
 }
 
+qreal QskStackBoxAnimator::transientIndex() const
+{
+    return m_transientIndex;
+}
+
+void QskStackBoxAnimator::advance( qreal progress )
+{
+    qreal transientIndex;
+
+    if ( qFuzzyIsNull( progress ) )
+    {
+        transientIndex = m_startIndex;
+    }
+    else if ( qFuzzyCompare( progress, 1.0 ) )
+    {
+        transientIndex = m_endIndex;
+    }
+    else
+    {
+        const auto box = stackBox();
+
+        auto startIndex = m_startIndex;
+        auto endIndex = m_endIndex;
+
+        if ( startIndex == 0 )
+        {
+            if ( endIndex == box->itemCount() - 1 )
+                startIndex += box->itemCount();
+        }
+        else if ( startIndex == box->itemCount() - 1 )
+        {
+            if ( endIndex == 0 )
+                endIndex += box->itemCount();
+        }
+
+        transientIndex = startIndex + ( endIndex - startIndex ) * progress;
+    }
+
+    if ( !qskFuzzyCompare( m_transientIndex, transientIndex ) )
+    {
+        m_transientIndex = transientIndex;
+        advanceIndex( progress );
+
+        Q_EMIT stackBox()->transientIndexChanged( m_transientIndex );
+    }
+}
+
 QskStackBoxAnimator1::QskStackBoxAnimator1( QskStackBox* parent )
     : QskStackBoxAnimator( parent )
     , m_orientation( Qt::Horizontal )
@@ -141,7 +189,7 @@ void QskStackBoxAnimator1::setup()
     m_isDirty = true;
 }
 
-void QskStackBoxAnimator1::advance( qreal value )
+void QskStackBoxAnimator1::advanceIndex( qreal value )
 {
     auto stackBox = this->stackBox();
     const bool isHorizontal = m_orientation == Qt::Horizontal;
@@ -243,7 +291,7 @@ void QskStackBoxAnimator3::setup()
     }
 }
 
-void QskStackBoxAnimator3::advance( qreal value )
+void QskStackBoxAnimator3::advanceIndex( qreal value )
 {
     if ( auto item1 = itemAt( 0 ) )
         item1->setOpacity( 1.0 - value );

src/layouts/QskStackBoxAnimator.h

@@ -28,13 +28,20 @@ class QSK_EXPORT QskStackBoxAnimator : public QObject, public QskAnimator
     int startIndex() const;
     int endIndex() const;
 
+    qreal transientIndex() const;
+
   protected:
     QskStackBox* stackBox() const;
     QQuickItem* itemAt( int index ) const;
 
   private:
+    void advance( qreal value ) override final;
+    virtual void advanceIndex( qreal value ) = 0;
+
     int m_startIndex;
     int m_endIndex;
+
+    qreal m_transientIndex;
 };
 
 class QSK_EXPORT QskStackBoxAnimator1 : public QskStackBoxAnimator
@@ -52,7 +59,7 @@ class QSK_EXPORT QskStackBoxAnimator1 : public QskStackBoxAnimator
     bool eventFilter( QObject*, QEvent* ) override;
 
     void setup() override;
-    void advance( qreal value ) override;
+    void advanceIndex( qreal value ) override;
     void done() override;
 
   private:
@@ -74,7 +81,7 @@ class QSK_EXPORT QskStackBoxAnimator3 : public QskStackBoxAnimator
 
   protected:
     void setup() override;
-    void advance( qreal value ) override;
+    void advanceIndex( qreal value ) override;
     void done() override;
 };