widget-canvas-ex-1.cpp

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// Copyright (C) 2025 The Qt Company Ltd.

// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

#include <QtCanvasPainter/qcanvaspainterwidget.h>

#include <QtCanvasPainter/qcanvaspainter.h>

#include <QtCanvasPainter/qcanvasimage.h>

//![0]

class MyWidget : public QCanvasPainterWidget

public:

    QCanvasOffscreenCanvas canvas;

    QCanvasImage canvasImage;

    void graphicsResourcesInvalidated() override

        canvas = {}; // so that the next prePaint() will recreate and redraw the canvas

    void prePaint(QCanvasPainter *p) override

        if (canvas.isNull()) {

            canvas = p->createCanvas(QSize(320, 240));

            beginCanvasPainting(canvas);

            p->beginPath();

            p->circle(160, 120, 20);

            p->setFillStyle(Qt::red);

            p->fill();

            endCanvasPainting();

            canvasImage = p->addImage(canvas, QCanvasPainter::ImageFlag::Repeat);

    void paint(QCanvasPainter *p) override

        // use canvasImage as a brush or with drawImage()

};

//![0]