[Bug] Why QDialog display empty rarely.

[brucezcg]

I create a class inherit from QDialog. it run well most of the time, but rarely display empty.
The good one looks like this.

And the abnormal status like this.

[brucezcg]

Any one can help?

[VRonin]

without any code it's like guessing the number of water drops in the Atlantic ocean.

[brucezcg]

@VRonin

#include "dlgbank.h"
#include "ui_dlgbank.h"

DlgBank::DlgBank(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::DlgBank)
{
    ui->setupUi(this);
    setWindowTitle(tr("BANK"));
    setWindowFlags(windowFlags()&~Qt::WindowContextHelpButtonHint);

    //Row Enable
    ZWgtHMITitle* title = new ZWgtHMITitle(this);

    ui->hLayoutEnable->addWidget(title, 10);
    title->setTitles(tr("Enable"));
    for(int col=1; col<9; col++) {
        QHBoxLayout* layout = new QHBoxLayout(this);
        HZSwitch* edt=new HZSwitch(this);
        layout->addWidget(edt);
        layout->setAlignment(edt,Qt::AlignCenter);

        mSWEnables.push_back(edt);
        connect(edt, &HZSwitch::toggled, this, &DlgBank::slt_swToggled);
        ui->hLayoutEnable->addLayout(layout, 5);
    }

    //Row Exposure
    title = new ZWgtHMITitle(this);
    ui->gridLayout->addWidget(title,0,0);
    ui->gridLayout->setColumnStretch(0,10);
    for(int col=1; col<9; col++) {
        ui->gridLayout->setColumnStretch(col, 5);
        {
            ZLineEdit* edt=new ZLineEdit(this);
            edt->setIgnoreNotChange(false);
            vector<HVarUI> vars;
            mEdtExposures.push_back(edt);
            HVarUICommon::addInt(vars, HCMDFULLTAG_END, tr("Exposure(us)"), 1200, 25, 999999);
            HVarUICommon::cfgUiItem(vars.at(0), title, edt);
            connect(edt, &ZLineEdit::sig_edtFinish, this, &DlgBank::slt_edtFinish);
            ui->gridLayout->addWidget(edt,0,col);
            edt->clearFocus();
        }
    }
    //Row Gain
    title = new ZWgtHMITitle(this);
    ui->gridLayout->addWidget(title,1,0);
    for(int col=1; col<9; col++) {
        ZComboBox* cbx=new ZComboBox(this);
        mCbxGains.push_back(cbx);
        vector<HVarUI> vars;
        vector<pair<int, QString>> parms;
        parms.push_back(make_pair(1, tr("1")));
        parms.push_back(make_pair(2, tr("2")));
        parms.push_back(make_pair(3, tr("3")));
        parms.push_back(make_pair(4, tr("4")));
        parms.push_back(make_pair(6, tr("6")));
        parms.push_back(make_pair(8, tr("8")));
        HVarUICommon::addList(vars, HCMDFULLTAG_END, tr("Gain"), parms, 4);
        HVarUICommon::cfgUiItem(vars.at(0), title, cbx);
        connect(cbx, SIGNAL(currentIndexChanged(int)), this, SLOT(slt_currentIndexChanged(int)));
        ui->gridLayout->addWidget(cbx,1,col);
    }

    this->setFixedSize(800,200);
    setTabOrder(mSWEnables.last(),mEdtExposures.first());
}

DlgBank::~DlgBank()
{
    delete ui;
}

void DlgBank::setBanks(const QList<Bank> &banks)
{
    mBanks = banks;
    for(int i=0; i<mBanks.length()&&i<8; i++) {
        const Bank bk = mBanks.at(i);
        mSWEnables[i]->setToggle(bk.mbEnable);
        mEdtExposures[i]->setText(QString::number(bk.mExposure));
        mCbxGains[i]->setCurrentByVal(bk.mGain);
    }
}

void DlgBank::slt_currentIndexChanged(int index)
{
    Q_UNUSED(index)
}

void DlgBank::slt_edtFinish(const QString &txt)
{
    ZLineEdit* edt = static_cast<ZLineEdit*>(sender());
    edt->clearFocus();
    int idx = mEdtExposures.indexOf(edt);
    if(mBanks.length()>idx && idx>=0 && !txt.isEmpty() ) {
        mBanks[idx].mExposure = txt.toUInt();
        QString cmd = HMenuProtocol::pack_BANK(mBanks);
        if(!cmd.isEmpty()) {
            menu_commands(cmd);
        }
    }
}

void DlgBank::slt_swToggled(bool bToggle)
{
    int idx = mSWEnables.indexOf(static_cast<HZSwitch*>(sender()));
    if(mBanks.length()>idx && idx>=0) {
        mBanks[idx].mbEnable = bToggle;
        QString cmd = HMenuProtocol::pack_BANK(mBanks);
        if(!cmd.isEmpty()) {
            menu_commands(cmd);
        }
    }
}

void DlgBank::send_cmd(const CmdFrame &cmd)
{
    emit sig_send_cmd(cmd);
}

[jsulm]

@brucezcg Can you also show how you create the dialog and show it?
If the dialog is empty then most probably your event loop is blocked.

[brucezcg]

@VRonin The phenomena is strange, in the empty status, although I couldn't see the controls(such as the switch button) but if I move mouse to the position of the button(it should be), all the controls will turn to display.

[brucezcg]

Just like the dialog doesn't call paint() automatically.

[brucezcg]

@jsulm Thanks.

I create the dialog in a Wdiget's constructor function like this.
{
……
mDialogBank = new DlgBank(this);
}

//Click button display the dialog.
void Wgt_Tuning::on_btnBank_clicked()
{
//Display the dialog.
if (QDialog::Accepted == mDialogBank->exec()) {
}
}

[jsulm]

@brucezcg On which platform do you have this behaviour?
You also could try to run through debugger and check the stack trace when this happens.

[brucezcg]

@jsulm Qt 5.12.3 mingw7 32bit.
This phenomena is never occur on my PC, It occurred on my college's PC rarely.

[jsulm]

@brucezcg What is the OS on that PC and graphics driver?

[brucezcg]

@jsulm Win10 & Intel HD Graphics 520

[jsulm]

@brucezcg Try to update the graphics driver.

[brucezcg]

@jsulm But this is very rarely. most of the time the dialog display well.

[mrjj]

@brucezcg
Hi
maybe a rare driver bug. :)

In any case, if possible you should test if a new driver helps on your college's PC.

[brucezcg]

@mrjj Thanks for the reply, and I try to use QWidget instead of QDialog.

[Christian Ehrlicher]

Maybe related to https://forum.qt.io/topic/107728/qscrollarea-causes-crash-on-close/4 ? Please try with 5.12.5