From a48943e68fd423b566637c9350544cb12cc88e0c Mon Sep 17 00:00:00 2001
From: Uwe Rathmann <Uwe.Rathmann@tigertal.de>
Date: Fri, 9 Dec 2022 12:07:46 +0100
Subject: [PATCH] initial implementation for the playground/gradients added.
 This demo is intended to compare how gradients are rendered with the
 different QSkinny backends to the raster paint engine

---
 playground/gradients/gradients.pro |  16 +++
 playground/gradients/main.cpp      | 150 +++++++++++++++++++++++++++++
 playground/playground.pro          |   3 +-
 3 files changed, 168 insertions(+), 1 deletion(-)
 create mode 100644 playground/gradients/gradients.pro
 create mode 100644 playground/gradients/main.cpp

diff --git a/playground/gradients/gradients.pro b/playground/gradients/gradients.pro
new file mode 100644
index 00000000..3cd3c87b
--- /dev/null
+++ b/playground/gradients/gradients.pro
@@ -0,0 +1,16 @@
+CONFIG += qskexample
+
+QT += widgets quickwidgets
+
+HEADERS += 
+
+SOURCES += \
+    main.cpp
+
+linux {
+
+    pedantic {
+        QMAKE_CXXFLAGS += -isystem $$[QT_INSTALL_HEADERS]/QtQuickWidgets
+        QMAKE_CXXFLAGS += -isystem $$[QT_INSTALL_HEADERS]/QtWidgets
+    }
+}
diff --git a/playground/gradients/main.cpp b/playground/gradients/main.cpp
new file mode 100644
index 00000000..e3aa704c
--- /dev/null
+++ b/playground/gradients/main.cpp
@@ -0,0 +1,150 @@
+/******************************************************************************
+ * QSkinny - Copyright (C) 2016 Uwe Rathmann
+ * This file may be used under the terms of the 3-clause BSD License
+ *****************************************************************************/
+
+#include <SkinnyNamespace.h>
+#include <QskControl.h>
+#include <QskGradient.h>
+
+#include <QWidget>
+#include <QApplication>
+#include <QQuickWidget>
+#include <QHBoxLayout>
+#include <QPainter>
+
+class BoxQsk: public QQuickWidget
+{
+  public:
+    BoxQsk( QWidget* parent = nullptr )
+        : QQuickWidget( parent )
+    {
+        setSizePolicy( QSizePolicy::Ignored, QSizePolicy::Ignored );
+
+        setContentsMargins( QMargins() );
+        setResizeMode( QQuickWidget::SizeRootObjectToView );
+
+        m_control = new QskControl();
+        setContent( QUrl(), nullptr, m_control );
+    }
+
+    void showGradient( const QGradient& gradient )
+    {
+        QskGradient qskGradient( gradient );
+
+        /*
+            Eliminate the useless offsets that have been added to work around
+            QGradients limitation to have stops at the same position
+         */
+
+        auto stops = qskGradient.stops();
+        for ( int i = 1; i < stops.count(); i++ )
+        {
+            if ( stops[i].position() - stops[i-1].position() < 1e-5 )
+                stops[i].setPosition( stops[i-1].position() );
+        }
+
+        qskGradient.setStops( stops );
+
+        m_control->setBackground( qskGradient );
+    }
+
+  private:
+    QskControl* m_control;
+};
+
+class BoxQt: public QWidget
+{ 
+  public:
+    BoxQt( QWidget* parent = nullptr )
+        : QWidget( parent )
+    {
+        setContentsMargins( QMargins() );
+        setSizePolicy( QSizePolicy::Ignored, QSizePolicy::Ignored );
+    }
+
+    void showGradient( const QGradient& gradient )
+    {
+        m_gradient = gradient;
+        m_gradient.setCoordinateMode( QGradient::ObjectMode );
+
+        update();
+    }
+
+  protected:
+    void paintEvent( QPaintEvent* ) override
+    {
+        QPainter painter( this );
+        painter.fillRect( contentsRect(), m_gradient );
+    }
+
+  private:
+    QGradient m_gradient;
+};
+
+class GradientBox: public QWidget
+{
+    Q_OBJECT
+
+  public:
+    GradientBox( QWidget* parent = nullptr )
+        : QWidget( parent )
+    {
+        m_qtBox = new BoxQt();
+        m_qskBox = new BoxQsk();
+
+        auto layout = new QHBoxLayout( this );
+        layout->addWidget( m_qskBox );
+        layout->addWidget( m_qtBox );
+
+        showGradient( { Qt::green, Qt::red, Qt::yellow, Qt::cyan, Qt::darkCyan } );
+    }
+
+    void showGradient( const QVector< QColor >& colors )
+    {
+        const auto step = 1.0 / colors.size();
+
+        QGradientStops stops;
+
+        for ( int i = 0; i < colors.size(); i++ )
+        {
+            auto pos = i * step;
+            if ( i > 0 )
+                pos += 1e-6; // QGradient does not support stops at the same position
+
+            stops += { pos, colors[i] };
+            stops += { ( i + 1 ) * step, colors[i] };
+        }
+
+        QLinearGradient gradient( 0.0, 0.0, 0.0, 1.0 );
+        gradient.setStops( stops );
+
+        showGradient( gradient );
+    }
+
+  public Q_SLOTS:
+    void showGradient( const QGradient& gradient )
+    {
+        m_qtBox->showGradient( gradient );
+        m_qskBox->showGradient( gradient );
+    }
+
+  private:
+    BoxQt* m_qtBox;
+    BoxQsk* m_qskBox;
+};
+
+int main( int argc, char** argv )
+{
+    QApplication app( argc, argv );
+    Skinny::init(); // we need a skin
+
+    GradientBox box;
+
+    box.resize( 600, 600 );
+    box.show();
+
+    return app.exec();
+}
+
+#include "main.moc"
diff --git a/playground/playground.pro b/playground/playground.pro
index 1cdf0540..509d40a3 100644
--- a/playground/playground.pro
+++ b/playground/playground.pro
@@ -19,5 +19,6 @@ qtHaveModule(webengine) {
 qtHaveModule(quickwidgets) {
 
     SUBDIRS += \
-        grids
+        grids \
+        gradients
 }