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General message class in trouble with const function

Ingo Förster
Last Modified: 2020-01-26
In my QT app I have a global class to show error messages.  This is working well in common functions.

int32 MdiChildHex::startHex(QString strBurnDrive)
    int32 ret = ::SetBurnDevice(strBurnDrive.at(0).toLatin1());
    if(showDiskbutlerMessage(ret, this)==false) {
        thisSuccessfullCreated = false;

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But if the function will hold a "const" in it, the function is not recognized-

int32 MdiChildHex::ReadSector(int32 sectorIndex) const
    char *buf = new char[2352];
    QByteArray mdata;

    int32 ret = ::ReadSectors(BS_CURRENT_DEVICE, sectorIndex, 1, BS_IMG_ISO, buf, bufferSize);
    showDiskbutlerMessage(ret, this);

    QByteArray byteArray = QByteArray::fromRawData(buf, bufferSize);


    hexView->setData(new QHexView::DataStorageArray(byteArray));

    return ret;

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The message I see in QTCreator is:
mdichild_hex.cpp:116:5: error: no matching function for call to 'showDiskbutlerMessage'
messanger.h:7:6: note: candidate function not viable: no known conversion from 'const MdiChildHex *' to 'QWidget *' for 2nd argument


#include <QtWidgets>
#include "FoxSDKExport.h"

bool showDiskbutlerMessage(int32 nError, QWidget* parent);

#endif // MESSANGER_H

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#include "messanger.h"
#include "utils_common.h"
#include <QMessageBox>

bool showDiskbutlerMessage(int32 nError, QWidget* parent){

    if (nError != BS_SDK_ERROR_NO){

        TCHAR chError[2048];
        int32 nLength = 2048;

        ::GetText(nError,chError, &nLength);

        QString errDesc;
#if defined (WIN32)
        errDesc= QString::fromUtf16(chError);
        errDesc= QString::fromUtf8(chError);

        QMessageBox::information(getMainWindow(),  QWidget::tr("Diskbutler Error"),
        return false;

    return true;

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What is the secret here with const?
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