Issue printing in QtQuick app

[Cyrille de Brebisson]

Hello,

I am trying to print in a QtQuick app.
in my main.cpp, I have changed the QGuiApplication into a QApplication and I have added printsupport in my .pro file.

I have a button in qml that calls:

void CBSModel::print()
{
    qDebug() << 1;
    QPrinter printer(QPrinter::HighResolution);
    QPrintDialog dialog(&printer, nullptr);
    dialog.setWindowTitle(tr("Print couder mask"));
    if (dialog.exec() != QDialog::Accepted) return;
}

But calling this function causes a crash once the function returns...
Is there anything that I am missing that is causing such a crash?
I have no problem calling other pieces of code from QML.
removing the call to dialog.exec() makes the crash go away.

Cyrille

[SGaist]

Hi,

What version of Qt are you using ?
On what OS ?
Can you post the stack trace ?

[Cyrille de Brebisson]

Hello,

QT 5.11.2
I get a "SIGSEV"

Here is the raw data...

onecoreuap\shell\windows.storage\viewsettings.cpp(3603)\windows.storage.dll!76081EBE: (caller: 76081F4F) ReturnHr(1) tid(180) 80004005 Unspecified error

1 QQuickPointerMouseEvent::isDoubleClickEvent qquickevents.cpp 1514 0x217ecd8b
2 QQuickWindowPrivate::deliverMatchingPointsToItem qquickwindow.cpp 2540 0x2181ff02
3 QQuickWindowPrivate::deliverPressOrReleaseEvent qquickwindow.cpp 2524 0x2182121b
4 QQuickWindowPrivate::deliverMouseEvent qquickwindow.cpp 1761 0x21821556
5 QQuickWindowPrivate::deliverPointerEvent qquickwindow.cpp 2317 0x21821f9f
6 QQuickWindowPrivate::handleMouseEvent qquickwindow.cpp 2152 0x21822bba
7 QQuickWindow::mousePressEvent qquickwindow.cpp 2119 0x21822fe4
8 QWindow::event qwindow.cpp 2242 0xcb54880
9 QQuickWindow::event qquickwindow.cpp 1634 0x218247ab
10 QApplicationPrivate::notify_helper qapplication.cpp 3727 0x2c5e85ca
11 QApplication::notify qapplication.cpp 3099 0x2c5efb83
12 QCoreApplication::notifyInternal2 qcoreapplication.cpp 1048 0x1a514e01
13 QCoreApplication::sendSpontaneousEvent qcoreapplication.h 237 0xcb4acae
14 QGuiApplicationPrivate::processMouseEvent qguiapplication.cpp 2081 0xcb4acae
15 QGuiApplicationPrivate::processWindowSystemEvent qguiapplication.cpp 1816 0xcb4c589
16 QWindowSystemInterface::sendWindowSystemEvents qwindowsysteminterface.cpp 1032 0xcb2df99
17 QWindowsGuiEventDispatcher::sendPostedEvents qwindowsguieventdispatcher.cpp 82 0x3e2adcb4
18 qt_internal_proc(HWND__ *, unsigned int, unsigned int, long) *16 qeventdispatcher_win.cpp 237 0x1a5650d1
19 USER32!AddClipboardFormatListener 0x7546be6b
20 USER32!DispatchMessageW 0x7546833a
21 USER32!DispatchMessageW 0x75467bee
22 USER32!DispatchMessageW 0x754679d0
23 QEventDispatcherWin32::processEvents qeventdispatcher_win.cpp 629 0x1a56482c
24 QWindowsGuiEventDispatcher::processEvents qwindowsguieventdispatcher.cpp 74 0x3e2adc87
25 QEventLoop::processEvents qeventloop.cpp 136 0x1a5134b0
26 QEventLoop::exec qeventloop.cpp 214 0x1a513908
27 QCoreApplication::exec qcoreapplication.cpp 1336 0x1a51bff6
28 QGuiApplication::exec qguiapplication.cpp 1761 0xcb415c6
29 QApplication::exec qapplication.cpp 2901 0x2c5e84a9
30 qMain main.cpp 40 0x4018d4
31 WinMain *16 qtmain_win.cpp 104 0x40ce65
32 main 0x431a3d

[SGaist]

Can you provide a minimal compilable example that triggers this ?

[Cyrille de Brebisson]

Hello,

After a lot of work, I found the following:

if you use the first version of the "print" code, things work
if you use the 2nd version (with the listView), it crashes!!!!
To reproduce the bug, compile/start the app. Press on the "print" button, click on cancel on the print dialog box, wait 1~2 seconds... it crashes...

main.qml // This version works...

import QtQuick 2.9
import QtQuick.Controls 2.4
import "qrc:/qml/" //import the qml folder
import CBSModel 1.0

ApplicationWindow { visible: true; width: 600; height: 600;
//        SwipeView { anchors.fill: parent;
                Button   { text: qsTr("Print"); onPressed: CBSModel.printCouder() }
//        }
}

main.qml // This version crashes!

import QtQuick 2.9
import QtQuick.Controls 2.4
import "qrc:/qml/" //import the qml folder
import CBSModel 1.0

ApplicationWindow { visible: true; width: 600; height: 600;
        SwipeView { anchors.fill: parent;
                Button   { text: qsTr("Print"); onPressed: CBSModel.printCouder() }
        }
}

main.cpp

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQuickStyle>
#include <QIcon>
#include "model.h"

CBSModel *CBSModel::singleton= nullptr;

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    QIcon iconApplication;
#ifdef WINDOWS
    iconApplication = readIcoFile("qrc:/Resources/cbscope.ico");
#else
    iconApplication.addFile("qrc:/Resources/cbscope.icns");
#endif
    qmlRegisterSingletonType<CBSModel>("CBSModel", 1, 0, "CBSModel", CBSModel::SingletonProvider);
    QApplication app(argc, argv);
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/qml/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;
        int ret= app.exec();
    return ret;
}

model.h

#ifndef CBSMODEL_H
#define CBSMODEL_H
#include <QObject>
#include <QQmlEngine>
#include <QPrinter>
#include <QPainter>
#include <QPrintDialog>

class CBSModel : public QObject {
    Q_OBJECT
public:
    CBSModel(QObject *parent=nullptr): QObject(parent) { }
      static CBSModel *singleton;
    static QObject *SingletonProvider(QQmlEngine *engine, QJSEngine *scriptEngine)
    {   (void)engine; (void)scriptEngine;
        if (singleton==nullptr) singleton= new CBSModel();    return singleton;
    }
    Q_INVOKABLE void printCouder()
    {
        QPrinter printer(QPrinter::HighResolution);
        QPrintDialog dialog(&printer, nullptr);
        dialog.setWindowTitle(tr("Print couder mask"));
        if (dialog.exec() != QDialog::Accepted) return;
        printer.setOutputFileName("couder.ps");
        QRect area(printer.pageRect());
        int dpi= printer.resolution();
        QPoint c= area.center();
        QPainter painter;
        painter.begin(&printer);
        painter.end();
    }
};

#endif

Cyrille

[Cyrille de Brebisson]

This post is deleted!

[Cyrille de Brebisson]

hello

Is there any way to turn on in QtCreator buffer overruns detection similar to the ones build in Visual Studio?

Cyrille

[SGaist]

I am not aware of such a feature (it doesn't mean that it doesn't exists though), but you can also use VS to build your application and use the tools you need.