From 929b7a43fd3649a4806f52483cf0e08214cb93e3 Mon Sep 17 00:00:00 2001
From: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date: Wed, 5 Jun 2024 10:34:19 +0200
Subject: [PATCH] gradient rendering fixed

---
 playground/shadows/ArcPage.cpp     | 48 +++++++++++++++++++++++-------
 playground/shadows/ShadowedArc.cpp | 20 ++++---------
 playground/shadows/ShadowedArc.h   |  5 ++--
 src/nodes/QskArcRenderer.cpp       | 15 ++++++----
 4 files changed, 55 insertions(+), 33 deletions(-)

diff --git a/playground/shadows/ArcPage.cpp b/playground/shadows/ArcPage.cpp
index e8618e04..25498877 100644
--- a/playground/shadows/ArcPage.cpp
+++ b/playground/shadows/ArcPage.cpp
@@ -48,24 +48,50 @@ namespace
             }
         }
     };
+
+    class Arc : public ShadowedArc
+    {
+      public:
+        Arc()
+        {
+            setStartAngle( 45.0 );
+            setSpanAngle( 270.0 );
+            setThickness( 10.0 );
+
+            setBorderWidth( 2.0 );
+            setBorderColor( Qt::black );
+
+#if 0
+            const QskGradientStops stops =
+            {
+                { 0.1, Qt::darkRed  },
+                { 0.1, Qt::darkYellow },
+                { 0.5, Qt::darkYellow },
+                { 0.5, Qt::darkBlue },
+                { 0.75, Qt::darkBlue },
+                { 0.75, Qt::darkRed }
+            };
+#else
+            const QskGradientStops stops =
+            {
+                { 0.1, Qt::darkRed  },
+                { 0.5, Qt::darkYellow },
+                { 0.75, Qt::darkBlue },
+                { 1.0, Qt::darkRed }
+            };
+#endif
+
+            setFillGradient( stops );
+        }
+    };
 }
 
 ArcPage::ArcPage( QQuickItem* parent )
     : QskLinearBox( Qt::Vertical, parent )
 {
-    auto arc = new ShadowedArc();
+    auto arc = new Arc();
     arc->setMargins( 40 ); // some extra space for testing the offsets
 
-    {
-        // initial settings
-        arc->setStartAngle( 45.0 );
-        arc->setSpanAngle( 270.0 );
-        arc->setThickness( 10.0 );
-
-        arc->setBorderWidth( 2.0 );
-        arc->setBorderColor( Qt::darkBlue );
-    }
-
     auto panel = new ControlPanel( arc );
     panel->setSizePolicy( Qt::Vertical, QskSizePolicy::Fixed );
 
diff --git a/playground/shadows/ShadowedArc.cpp b/playground/shadows/ShadowedArc.cpp
index 6337bf9a..8bf9ab47 100644
--- a/playground/shadows/ShadowedArc.cpp
+++ b/playground/shadows/ShadowedArc.cpp
@@ -101,17 +101,7 @@ ShadowedArc::ShadowedArc( QQuickItem* parent )
 
     setArcMetrics( { 0.0, 360.0, 1.0, Qt::RelativeSize } );
 
-    //setFillColor( Qt::darkRed );
-
-    const QskGradientStops stops =
-    {
-        { 0.1, Qt::darkRed  },
-        { 0.5, Qt::darkYellow },
-        { 0.75, Qt::darkBlue },
-        { 1.0, Qt::darkRed }
-    };
-
-    setGradientHint( Arc, stops );
+    setFillGradient( Qt::white );
 
     setBorderWidth( 0 );
     setBorderColor( Qt::gray );
@@ -226,14 +216,14 @@ qreal ShadowedArc::blurRadius() const
     return shadowMetrics().blurRadius();
 }
 
-void ShadowedArc::setFillColor( const QColor& color )
+void ShadowedArc::setFillGradient( const QskGradient& gradient )
 {
-    setColor( Arc, color );
+    setGradientHint( Arc, gradient );
 }
 
-QColor ShadowedArc::fillColor() const
+QskGradient ShadowedArc::fillGradient() const
 {
-    return color( Arc );
+    return gradientHint( Arc );
 }
 
 void ShadowedArc::setShadowColor( const QColor& color )
diff --git a/playground/shadows/ShadowedArc.h b/playground/shadows/ShadowedArc.h
index c8f486d3..2f683e26 100644
--- a/playground/shadows/ShadowedArc.h
+++ b/playground/shadows/ShadowedArc.h
@@ -9,6 +9,7 @@
 
 class QskShadowMetrics;
 class QskArcMetrics;
+class QskGradient;
 
 class ShadowedArc : public QskControl
 {
@@ -35,7 +36,7 @@ class ShadowedArc : public QskControl
     qreal blurRadius() const;
 
     QColor borderColor() const;
-    QColor fillColor() const;
+    QskGradient fillGradient() const;
     QColor shadowColor() const;
 
   public Q_SLOTS:
@@ -52,7 +53,7 @@ class ShadowedArc : public QskControl
     void setBlurRadius( qreal );
 
     void setBorderColor( const QColor& );
-    void setFillColor( const QColor& );
+    void setFillGradient( const QskGradient& );
     void setShadowColor( const QColor& );
 
   private:
diff --git a/src/nodes/QskArcRenderer.cpp b/src/nodes/QskArcRenderer.cpp
index 211ff994..8022f98a 100644
--- a/src/nodes/QskArcRenderer.cpp
+++ b/src/nodes/QskArcRenderer.cpp
@@ -166,15 +166,20 @@ namespace
             it.advance(); // the first stop is always covered by the contour
         }
 
-        const auto stepCount = arcLineCount();
-        const auto stepSize = ( m_radians2 - m_radians1 ) / ( stepCount - 1 );
+        const auto count = arcLineCount();
 
-        for ( int i = 0; i < stepCount; i++ )
+        const qreal stepMax = count - 1;
+        const auto stepSize = ( m_radians2 - m_radians1 ) / stepMax;
+
+        for ( int i = 0; i < count; i++ )
         {
-            const auto progress = qreal( i ) / stepCount;
+            const auto progress = i / stepMax;
 
-            for ( ; it.position() < progress; it.advance() )
+            while( !it.isDone() && ( it.position() < progress ) )
+            {
                 setFillLine( radiansAt( it.position() ), it.color(), *l++ );
+                it.advance();
+            }
 
             const auto color = it.colorAt( progress );
             setFillLine( m_radians1 + i * stepSize, color, *l++ );