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Details

Type: Bug
Resolution: Fixed
Priority: P1: Critical
Fix Version/s: 6.2.8, 6.4.3, 6.5.0, 6.6.0
Affects Version/s: 6.2.7, 6.4.2, 6.5.0 Beta1
Component/s: GUI: Painting, SVG Support
Labels:
- Reported_by_support_standard
Environment:
Windows 10 Pro 22H2, MSVC 2019 x64

Commits:
ce7b4c734 (dev), d1a32dfce (tqtc/lts-6.2), 15e007175 (6.4), b11608fa8 (6.5), 8f5075067 (dev)

Description

Code

// data.h
#ifndef DATA_H
#define DATA_H

#include <QByteArray>

// Need to split this into separate file because moc trips over the raw string literal
inline QByteArray getSvgData()
{
    return
            R"svg(<?xml version="1.0" encoding="UTF-8" standalone="no"?>
            <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
            <svg width="400" height="400" version="1.1" xmlns="http://www.w3.org/2000/svg">
                <circle style="fill:none;stroke:#c0c0c0;stroke-width:1" cx="200" cy="200" r="150" />
            </svg>)svg";
}

#endif

// main.cpp
#include "data.h"

#include <QtTest>
#include <QObject>
#include <QSvgRenderer>
#include <QImage>
#include <QPainter>

class tst_MyClass : public QObject
{
    Q_OBJECT

private slots:
    void QSvgRenderer_render()
    {
        QImage img(QSize(5120, 5120), QImage::Format_ARGB32_Premultiplied);
        QPainter p(&img);
        p.fillRect(QRect(0, 0, img.width(), img.height()), Qt::transparent);

        QSvgRenderer renderer(getSvgData());
        renderer.setViewBox(QRectF(45., 185., 30., 30.));
        QBENCHMARK
        {
            renderer.render(&p);
        }
        img.save("output.png");
    }
};

QTEST_MAIN(tst_MyClass)
#include "main.moc"

Benchmark results

********* Start testing of tst_MyClass *********
Config: Using QtTest library 5.15.12, Qt 5.15.12 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2019), windows 10
PASS   : tst_MyClass::initTestCase()
PASS   : tst_MyClass::QSvgRenderer_render()
RESULT : tst_MyClass::QSvgRenderer_render():
     2.2 msecs per iteration (total: 71, iterations: 32)
PASS   : tst_MyClass::cleanupTestCase()
Totals: 3 passed, 0 failed, 0 skipped, 0 blacklisted, 12342ms
********* Finished testing of tst_MyClass *********

********* Start testing of tst_MyClass *********
Config: Using QtTest library 6.2.7, Qt 6.2.7 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2019), windows 10
PASS   : tst_MyClass::initTestCase()
PASS   : tst_MyClass::QSvgRenderer_render()
RESULT : tst_MyClass::QSvgRenderer_render():
     180 msecs per iteration (total: 180, iterations: 1)
PASS   : tst_MyClass::cleanupTestCase()
Totals: 3 passed, 0 failed, 0 skipped, 0 blacklisted, 2623ms
********* Finished testing of tst_MyClass *********

********* Start testing of tst_MyClass *********
Config: Using QtTest library 6.4.2, Qt 6.4.2 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2019), windows 10
PASS   : tst_MyClass::initTestCase()
PASS   : tst_MyClass::QSvgRenderer_render()
RESULT : tst_MyClass::QSvgRenderer_render():
     180 msecs per iteration (total: 180, iterations: 1)
PASS   : tst_MyClass::cleanupTestCase()
Totals: 3 passed, 0 failed, 0 skipped, 0 blacklisted, 2926ms
********* Finished testing of tst_MyClass *********

********* Start testing of tst_MyClass *********
Config: Using QtTest library 6.5.0, Qt 6.5.0 (x86_64-little_endian-llp64 shared (dynamic) release build; by MSVC 2019), windows 10
PASS   : tst_MyClass::initTestCase()
PASS   : tst_MyClass::QSvgRenderer_render()
RESULT : tst_MyClass::QSvgRenderer_render():
     176 msecs per iteration (total: 176, iterations: 1)
PASS   : tst_MyClass::cleanupTestCase()
Totals: 3 passed, 0 failed, 0 skipped, 0 blacklisted, 3023ms
********* Finished testing of tst_MyClass *********

Possible workaround

If you don't need to regularly change the SVG viewport position and size, then you can get much better results by pre-rasterizing the SVG image into a QImage/QPixmap with a transparent background and then repeatedly calling QPainter::drawImage()/QPainter::drawPixmap() instead of repeatedly calling QSvgRenderer::render().

Use-case

The customer is porting an application that needs to to regularily adjust the viewport position or even change the SVG contents to generate an overlay on top of a live (large) image feed. Unfortunately, this means the workaround above cannot be used.