QskArcRenderer started with some boilerplate code

src/CMakeLists.txt

@@ -101,6 +101,7 @@ list(APPEND SOURCES
 
 list(APPEND HEADERS
     nodes/QskArcNode.h
+    nodes/QskArcRenderer.h
     nodes/QskArcShadowNode.h
     nodes/QskBasicLinesNode.h
     nodes/QskBoxNode.h
@@ -141,6 +142,7 @@ list(APPEND PRIVATE_HEADERS
 
 list(APPEND SOURCES
     nodes/QskArcNode.cpp
+    nodes/QskArcRenderer.cpp
     nodes/QskArcShadowNode.cpp
     nodes/QskBasicLinesNode.cpp
     nodes/QskBoxNode.cpp

src/nodes/QskArcRenderer.cpp

@@ -0,0 +1,164 @@
+/******************************************************************************
+ * QSkinny - Copyright (C) The authors
+ *           SPDX-License-Identifier: BSD-3-Clause
+ *****************************************************************************/
+
+#include "QskArcRenderer.h"
+#include "QskArcMetrics.h"
+#include "QskGradient.h"
+#include "QskVertex.h"
+
+#include <qsggeometry.h>
+
+static inline QskVertex::Line* qskAllocateLines(
+    QSGGeometry& geometry, int lineCount )
+{
+    geometry.allocate( 2 * lineCount ); // 2 points per line
+    return reinterpret_cast< QskVertex::Line* >( geometry.vertexData() );
+}
+
+static inline QskVertex::ColoredLine* qskAllocateColoredLines(
+    QSGGeometry& geometry, int lineCount )
+{
+    geometry.allocate( 2 * lineCount ); // 2 points per line
+    return reinterpret_cast< QskVertex::ColoredLine* >( geometry.vertexData() );
+}
+
+static inline int qskApproximatedCircumference( const QRectF& rect )
+{
+    const qreal a = rect.width();
+    const qreal b = rect.height();
+
+    const auto ratio = a / b;
+    if ( ratio > 0.9 || ratio < 1.1 )
+        return std::max( a, b ) * 2.0 * M_PI; // circle
+
+    // Srinivasa Ramanujan: https://en.wikipedia.org/wiki/Ellipse#Circumference
+
+    const qreal d1 = ( a - b );
+    const qreal d2 = ( a + b );
+    const qreal h = ( d1 * d1 ) / ( d2 * d2 );
+
+    return M_PI * d2 * ( 1.0 + ( 3 * h / ( 10 + sqrt( 4 - 3 * h ) ) ) );
+}
+
+static inline int qskStepCount( const QRectF& rect )
+{
+    const int length = qskApproximatedCircumference( rect );
+    return std::max( 3, qCeil( length / 3.0 ) );
+}
+
+namespace
+{
+    class Stroker
+    {
+      public:
+        Stroker( const QRectF&, const QskArcMetrics& metrics, qreal borderWidth );
+
+        int fillCount() const;
+        int borderCount() const;
+
+        void setBorderLines( QskVertex::Line* ) const;
+
+      private:
+        const QRectF& m_rect;
+        const QskArcMetrics& m_metrics;
+        const qreal m_borderWidth;
+    };
+}
+
+Stroker::Stroker( const QRectF& rect, const QskArcMetrics& metrics, qreal borderWidth )
+    : m_rect( rect )
+    , m_metrics( metrics )
+    , m_borderWidth( borderWidth )
+{
+    Q_ASSERT( metrics.sizeMode() == Qt::AbsoluteSize );
+}
+
+int Stroker::fillCount() const
+{
+    return 0; // TODO
+}
+
+int Stroker::borderCount() const
+{
+    if ( m_metrics.isNull() )
+        return 0;
+
+    int n = qskStepCount( m_rect );
+    if ( !m_metrics.isClosed() )
+    {
+        n = qCeil( n * qAbs( m_metrics.spanAngle() ) / 360.0 );
+        n += 1; // closing line
+    }
+
+    n *= 2; // inner/outer border
+    n += 1; // dummy line connection inner/outer border
+
+    return n;
+}
+
+void Stroker::setBorderLines( QskVertex::Line* lines ) const
+{
+    Q_UNUSED( lines );
+}
+
+void QskArcRenderer::renderBorderGeometry( const QRectF& rect,
+    const QskArcMetrics& metrics, qreal borderWidth, QSGGeometry& geometry )
+{
+    geometry.setDrawingMode( QSGGeometry::DrawTriangleStrip );
+
+    Stroker stroker( rect, metrics, borderWidth );
+
+    const auto lines = qskAllocateLines( geometry, stroker.borderCount() );
+    if ( lines )
+        stroker.setBorderLines( lines );
+}
+
+void QskArcRenderer::renderFillGeometry( const QRectF& rect,
+    const QskArcMetrics& metrics, qreal borderWidth, QSGGeometry& geometry )
+{
+    Q_UNUSED( rect );
+    Q_UNUSED( geometry );
+
+    Stroker stroker( rect, metrics, borderWidth );
+
+    const auto lines = qskAllocateColoredLines( geometry, stroker.fillCount() );
+    if ( lines )
+    {
+        // TODO
+    }
+}
+
+void QskArcRenderer::renderFillGeometry( const QRectF& rect,
+    const QskArcMetrics& metrics, QSGGeometry& geometry )
+{
+    renderFillGeometry( rect, metrics, 0.0, geometry );
+}
+
+bool QskArcRenderer::isGradientSupported(
+    const QskArcMetrics& metrics, const QskGradient& gradient )
+{
+    if ( metrics.isNull() || !gradient.isVisible() || gradient.isMonochrome() )
+        return true;
+
+    return gradient.type() == QskGradient::Stops;
+}
+
+void QskArcRenderer::renderArc( const QRectF& rect,
+    const QskArcMetrics& metrics, qreal borderWidth, const QColor& borderColor,
+    const QskGradient& gradient, QSGGeometry& geometry )
+{
+    Q_UNUSED( rect );
+    Q_UNUSED( metrics );
+    Q_UNUSED( borderWidth );
+    Q_UNUSED( borderColor );
+    Q_UNUSED( gradient );
+    Q_UNUSED( geometry );
+}
+
+void QskArcRenderer::renderArc( const QRectF& rect, const QskArcMetrics& metrics,
+    const QskGradient& gradient, QSGGeometry& geometry )
+{
+    renderArc( rect, metrics, 0, QColor(), gradient, geometry );
+}

src/nodes/QskArcRenderer.h

@@ -0,0 +1,51 @@
+/******************************************************************************
+ * QSkinny - Copyright (C) The authors
+ *           SPDX-License-Identifier: BSD-3-Clause
+ *****************************************************************************/
+
+#ifndef QSK_ARC_RENDERER_H
+#define QSK_ARC_RENDERER_H
+
+#include "QskGlobal.h"
+
+class QskArcMetrics;
+class QskGradient;
+
+class QSGGeometry;
+class QRectF;
+class QColor;
+
+namespace QskArcRenderer
+{
+    /*
+        Filling the geometry without any color information:
+            see QSGGeometry::defaultAttributes_Point2D()
+
+        - clip nodes
+        - using shaders setting the color information
+     */
+
+    QSK_EXPORT void renderBorderGeometry( const QRectF&,
+        const QskArcMetrics&, qreal borderWidth, QSGGeometry& );
+
+    QSK_EXPORT void renderFillGeometry( const QRectF&,
+        const QskArcMetrics&, qreal borderWidth, QSGGeometry& );
+
+    QSK_EXPORT void renderFillGeometry( const QRectF&,
+        const QskArcMetrics&, QSGGeometry& );
+
+    /*
+        Filling the geometry usually with color information:
+            see QSGGeometry::defaultAttributes_ColoredPoint2D()
+     */
+    QSK_EXPORT bool isGradientSupported( const QskArcMetrics&, const QskGradient& );
+
+    QSK_EXPORT void renderArc( const QRectF&,
+        const QskArcMetrics&, qreal borderWidth, const QColor& borderColor,
+        const QskGradient&, QSGGeometry& );
+
+    QSK_EXPORT void renderArc( const QRectF&, const QskArcMetrics&,
+        const QskGradient&, QSGGeometry& );
+}
+
+#endif