Child QFileDialog paint problem

kendavistoo

The QFileDialog displays as a transparent frame. I am including a small test program. Thanks!

#-------------------------------------------------
#
# Project created by QtCreator 2018-08-21T10:24:03
#
#-------------------------------------------------


QT       += core gui opengl multimedia multimediawidgets

TARGET = QFileDialogTest
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

CONFIG += c++11

SOURCES += \
        main.cpp \
        mainwindow.cpp \
        globalfunctions.cpp \
        mydialogclass.cpp

HEADERS += \
        globals.h \
        mainwindow.h \
         mydialogclass.h

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

globals.h :

#ifndef GLOBALS_H
#define GLOBALS_H

#include <iostream>
#include <cstdio>
#include <stdlib.h>
#include <string>
#include <stdio.h>

#include <QApplication>
#include <QColor>
#include <QCoreApplication>
#include <QDebug>
#include <QDesktopWidget>
#include <QDialog>
#include <QDir>
#include <QFile>
#include <QFileDialog>
#include <QMainWindow>
#include <QPaintDevice>
#include <QPainter>
#include <QPushButton>
#include <QRadioButton>
#include <QRect>
#include <QScreen>
#include <QString>
#include <QStringList>
#include <QWindow>
#include <QtCore>
#include <QtDebug>
#include <QtGui>

using std::cout;
using std::cin;

//==================== constants ====================

static const QColor G_RED           = QColor(255,0,0,255);
static const QColor G_GREEN         = QColor(0,255,0,255);
static const QColor G_BLUE          = QColor(0,0,255,255);

//==================== functions ====================

void gSizeAndCenterWidget (QWidget* widget, int width, int height);

#endif // GLOBALS_H

globalfunctions.cpp :

#ifndef GLOBALS_H
#include "globals.h"
#endif

//---------- gSizeAndCenterWidget ---------

void gSizeAndCenterWidget (QWidget* widget, int width, int height) {
    int x,y;
    int screenWidth;
    int screenHeight;

    QDesktopWidget* desktop = QApplication::desktop();

    screenWidth = desktop->width();
    screenHeight = desktop->height();

    x = (screenWidth - width)/2;
    y = (screenHeight - height)/2;

    widget->setGeometry (x, y, width, height);
}//gSizeAndCenterWidget

mainwindow.h :

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#ifndef GLOBALS_H
#include "globals.h"
#endif

#ifndef MYDIALOGCLASS_H
#include "mydialogclass.h"
#endif

const static int MW_WIDTH       = 500;
const static int MW_HEIGHT      = 400;

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    QPushButton     *dialogButt;
    MyDialogClass   *rootDialog;

protected:
    void paintEvent(QPaintEvent*);

private slots:
    void SlotDoDialog();
};

#endif // MAINWINDOW_H

mainwindow.cpp :

#include "mainwindow.h"

//---------- MainWindow Constructor ----------

MainWindow :: MainWindow(QWidget *parent) : QMainWindow(parent)
{
    qDebug()<<"CONSTRUCTOR   MainWindow";

    gSizeAndCenterWidget (this, MW_WIDTH, MW_HEIGHT);

    dialogButt  = new QPushButton("Do Dialog", this);
    dialogButt->setGeometry(100, 100, 100, 28);
    connect(dialogButt,&QPushButton::clicked,this, &MainWindow::SlotDoDialog);

    rootDialog = nullptr;
}

//---------- MainWindow Destructor ----------

MainWindow :: ~MainWindow()
{
    qDebug()<<"DESTRUCTOR   MainWindow";
}

//---------- SlotDoDialog ----------

void MainWindow :: SlotDoDialog(){

    if (rootDialog != nullptr) return;

    qDebug()<<"   SlotDoDialog";

    rootDialog = new MyDialogClass(this, Qt::Dialog);
    gSizeAndCenterWidget (rootDialog, (MW_WIDTH - 100), (MW_HEIGHT - 100));
    rootDialog->exec();
}

//---------- paintEvent ----------

void MainWindow :: paintEvent(QPaintEvent* event) {

    QPainter* painter = new QPainter(this);

    int x = (this->width() - 100) + (int)(50 + (rand() % 10));
    int y = (this->height() - 40);
    QRect myRect(x,y,8,8);
    painter->fillRect(myRect, G_RED);

    delete painter;

    update();
}

mydialogclass.h :

#ifndef MYDIALOGCLASS_H
#define MYDIALOGCLASS_H

#ifndef GLOBALS_H
#include "globals.h"
#endif

class MyDialogClass : public QDialog
{
public:
    MyDialogClass(QWidget *parent = nullptr, Qt::WindowFlags f = Qt::Dialog);
    ~MyDialogClass();

private:
    QPushButton     *anotherDialogButt;
    QPushButton     *fileDialogButt;

protected:
    void paintEvent(QPaintEvent*);

private slots:
    void slotDoAnotherDialog();
    void slotDoFileDialog();
};

#endif // MYDIALOGCLASS_H

mydialogclass.cpp :

#include "mydialogclass.h"

//---------- MyDialogClass CONSTRUCTOR ----------

MyDialogClass :: MyDialogClass(QWidget *parent, Qt::WindowFlags f) : QDialog (parent, f)
{
    qDebug()<<"CONSTRUCTOR   MyDialogClass";

    anotherDialogButt  = new QPushButton("Do Child Dialog", this);
    anotherDialogButt->setGeometry(100, 100, 150, 28);
    connect(anotherDialogButt,&QPushButton::clicked,this, &MyDialogClass::slotDoAnotherDialog);

    fileDialogButt  = new QPushButton("Do QFileDialog", this);
    fileDialogButt->setGeometry(100, 140, 150, 28);
    connect(fileDialogButt,&QPushButton::clicked,this, &MyDialogClass::slotDoFileDialog);
}

//---------- MyDialogClass DESTRUCTOR ----------

MyDialogClass :: ~MyDialogClass(){
    qDebug()<<"DESTRUCTOR   MyDialogClass";

}

//---------- paintEvent ----------

void MyDialogClass :: paintEvent(QPaintEvent *e) {

    QPainter* painter = new QPainter(this);

    int x = (this->width() - 100) + (int)(50 + (rand() % 10));
    int y = (this->height() - 40);
    QRect myRect(x,y,8,8);
    painter->fillRect(myRect, G_GREEN);

    delete painter;

    update();
}

//---------- slotDoAnotherDialog ----------

void MyDialogClass :: slotDoAnotherDialog(){

    qDebug()<<"   slotDoAnotherDialog";

    MyDialogClass *anotherDialog = new MyDialogClass(this);

    anotherDialog->exec();
}

//---------- slotDoFileDialog ----------

void MyDialogClass :: slotDoFileDialog(){
    qDebug()<<"   slotDoFileDialog";

    QString fileName = QFileDialog::getOpenFileName(this,
        "Open Image", "~/", "Image Files (*.png *.jpg *.bmp)");

    qDebug()<<"fileName:  "<<fileName;
}

main.cpp :

#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

mranger90

Calling update() in your paint event handler is a bad thing to do.

kendavistoo

I agree that calling update() in paintEvent() is not good, but it usually works.

The problem is solved. I am running Linux Mint, and the native dialog was not painting. Solved by setting the "QFileDialog::DontUseNativeDialog" option.

//---------- slotDoFileDialog ----------

void MyDialogClass :: slotDoFileDialog(){

    qDebug()<<"   slotDoFileDialog";

    QFileDialog myFileDialog(this, Qt::Dialog);
    myFileDialog.setOption(QFileDialog::DontUseNativeDialog, true);
    myFileDialog.setFileMode(QFileDialog::DirectoryOnly);
    myFileDialog.exec();
}