QPainter example, better performance in compare to canvas

QPainerExample/QPainerExample.pro

@@ -0,0 +1,27 @@
+QT += quick
+
+CONFIG += c++11
+
+# You can make your code fail to compile if it uses deprecated APIs.
+# In order to do so, uncomment the following line.
+#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
+
+SOURCES += \
+        main.cpp \
+        qquickcustomitem.cpp
+
+RESOURCES += qml.qrc
+
+# Additional import path used to resolve QML modules in Qt Creator's code model
+QML_IMPORT_PATH =
+
+# Additional import path used to resolve QML modules just for Qt Quick Designer
+QML_DESIGNER_IMPORT_PATH =
+
+# Default rules for deployment.
+qnx: target.path = /tmp/$${TARGET}/bin
+else: unix:!android: target.path = /opt/$${TARGET}/bin
+!isEmpty(target.path): INSTALLS += target
+
+HEADERS += \
+    qquickcustomitem.h

QPainerExample/main.cpp

@@ -0,0 +1,27 @@
+#include <QGuiApplication>
+#include <QQmlApplicationEngine>
+#include "qquickcustomitem.h"
+
+int main(int argc, char *argv[])
+{
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+#endif
+
+    QGuiApplication app(argc, argv);
+
+    QQmlApplicationEngine engine;
+
+    qmlRegisterType<QQuickCustomItem>("stackoverflow.qml", 1, 0, "Triangle");
+
+
+    const QUrl url(QStringLiteral("qrc:/main.qml"));
+    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
+                     &app, [url](QObject *obj, const QUrl &objUrl) {
+        if (!obj && url == objUrl)
+            QCoreApplication::exit(-1);
+    }, Qt::QueuedConnection);
+    engine.load(url);
+
+    return app.exec();
+}

QPainerExample/main.qml

@@ -0,0 +1,38 @@
+import QtQuick 2.15
+import QtQuick.Window 2.15
+import stackoverflow.qml 1.0
+
+Window {
+    width: 640
+    height: 480
+    visible: true
+    title: qsTr("Hello World")
+
+    Rectangle {
+        width: 200
+        height: 200
+        anchors.centerIn: parent
+        color: "lightgrey"
+
+        Triangle {
+            id: rect
+            width: 200
+            height: 202
+//            transformOrigin: Item.Top
+            color: "green"
+            onColorChanged: console.log("color was changed");
+//            PropertyAnimation on rotation {
+//                from: 0
+//                to: 360
+//                duration: 5000
+//                loops: Animation.Infinite
+//            }
+        }
+    }
+    Timer {
+        interval: 1000
+        repeat: true
+        running: true
+        onTriggered: rect.color = Qt.rgba(Math.random(),Math.random(),Math.random(),1);
+    }
+}

QPainerExample/qml.qrc

@@ -0,0 +1,5 @@
+<RCC>
+    <qresource prefix="/">
+        <file>main.qml</file>
+    </qresource>
+</RCC>

QPainerExample/qquickcustomitem.cpp

@@ -0,0 +1,49 @@
+#include "qquickcustomitem.h"
+
+QQuickCustomItem::QQuickCustomItem(QQuickPaintedItem *parent) :
+    QQuickPaintedItem(parent),
+    m_color(Qt::red),
+    m_needUpdate(true)
+{
+    setFlag(QQuickItem::ItemHasContents);
+}
+
+void QQuickCustomItem::paint(QPainter *painter)
+{
+
+    const int scale = 1;
+
+    QPen pen;
+    pen.setWidth(3);
+    pen.setDashPattern({ 0.0, 1.0 * scale, 1.0 * scale, 1.0 * scale });
+    pen.setColor(m_color);
+
+    QPainterPath path;
+//    path.moveTo(width() / 2, 0);
+//    path.lineTo(width(), height());
+//    path.lineTo(0, height());
+//    path.lineTo(width() / 2, 0);
+
+    qWarning()<<painter->window().width()<<" "<<painter->window().height();
+    path.moveTo(QPoint(100, 0));
+    path.arcTo(QRectF(0, 0, painter->window().width(), painter->window().height()), 90, 270);
+
+
+    painter->setPen(pen);
+    painter->drawPath(path);
+}
+
+QColor QQuickCustomItem::color() const
+{
+    return m_color;
+}
+
+void QQuickCustomItem::setColor(const QColor &color)
+{
+    if(m_color != color) {
+        m_color = color;
+        m_needUpdate = true;
+        update();
+        emit colorChanged();
+    }
+}

QPainerExample/qquickcustomitem.h

@@ -0,0 +1,29 @@
+#ifndef QQUICKCUSTOMITEM_H
+#define QQUICKCUSTOMITEM_H
+
+#include <QQuickPaintedItem>
+#include <QPainter>
+#include <QPainterPath>
+
+class QQuickCustomItem : public QQuickPaintedItem
+{
+    Q_OBJECT
+    Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged)
+public:
+    QQuickCustomItem(QQuickPaintedItem *parent = Q_NULLPTR);
+
+protected:
+    void paint(QPainter *painter);
+
+    QColor color() const;
+    void setColor(const QColor &color);
+
+private:
+    QColor m_color;
+    bool m_needUpdate;
+
+signals:
+    void colorChanged();
+};
+
+#endif // QQUICKCUSTOMITEM_H