qt-creator/tests/manual/qml/testprojects/pixelmetrics/PixelMeter.qml

// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0

import QtQuick 2.10

Canvas {
    width: 100
    height: 100

    function drawCornerMarkers(ctx)
    {
        var cornerMarkerSize = 10;

        ctx.beginPath();

        // top left
        ctx.moveTo(0, 0.5);
        ctx.lineTo(cornerMarkerSize, 0.5);
        ctx.moveTo(0.5, 0);
        ctx.lineTo(0.5, cornerMarkerSize);

        // top right
        ctx.moveTo(width - cornerMarkerSize, 0.5);
        ctx.lineTo(width, 0.5);
        ctx.moveTo(width - 0.5, 0);
        ctx.lineTo(width - 0.5, cornerMarkerSize);

        // bottom left
        ctx.moveTo(0, height - 0.5);
        ctx.lineTo(cornerMarkerSize, height - 0.5);
        ctx.moveTo(0.5, height - cornerMarkerSize);
        ctx.lineTo(0.5, height);

        // bottom right
        ctx.moveTo(width - cornerMarkerSize, height - 0.5);
        ctx.lineTo(width, height - 0.5);
        ctx.moveTo(width - 0.5, height - cornerMarkerSize);
        ctx.lineTo(width - 0.5, height);

        ctx.stroke();
    }

    function drawMetrics(ctx)
    {
        ctx.font = '9px sans-serif';

        // top left
        ctx.textAlign = "left";
        ctx.textBaseline = "top";
        ctx.fillStyle = Qt.rgba(0, 0, 1, 1);
        ctx.fillText(x + '|' + y, 1, 1);

        // size
        ctx.textAlign = "center";
        ctx.textBaseline = "middle";
        ctx.fillText(width + 'x' + height, width / 2, height / 2);

        // bottom right
        ctx.textAlign = "right";
        ctx.textBaseline = "bottom";
        ctx.fillText((x + width) + '|' + (y + height), width - 1, height - 1);
    }

    onPaint: {
        var ctx = getContext("2d");

        ctx.fillStyle = Qt.rgba(1, 0, 0, 0.2);
        ctx.fillRect(0, 0, width, height);

        drawCornerMarkers(ctx);
        drawMetrics(ctx);
    }
}