QFileSystemModel/QSortFilterProxyModel crash issue

filesystemusbmodeldialog.h
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#include "ui_filesystemusbmodelwidget.h"

#include <QWidget>
#include <QFileSystemModel>
#include <QItemDelegate>

class USBDriveFilterProxyModel;

class IconItemUsbDelegate : public QItemDelegate
{
public:
    IconItemUsbDelegate();
    QSize sizeHint ( const QStyleOptionViewItem & option, const QModelIndex & index ) const;
};

class IconFileSystemUsbModel : public QFileSystemModel
{
    Q_OBJECT
public:
    virtual QVariant data ( const QModelIndex & index, int role = Qt::DisplayRole ) const;

};

class FileSystemUsbModelDialog : public QWidget
{
    Q_OBJECT

public:
    explicit FileSystemUsbModelDialog(QWidget *parent);
    ~FileSystemUsbModelDialog();

private:
    Ui::FileSystemUsbModelWidget *ui;
    IconFileSystemUsbModel *dir;
    USBDriveFilterProxyModel *usbModel;

Q_SIGNALS:
    void signalFileSelected(QString);
};

#endif // FILESYSTEMUSBMODELDIALOG_H
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filesystemusbmodeldialog.cpp:
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#include "filesystemusbmodeldialog.h"
#include "usbdrivefilter.h"

IconItemUsbDelegate::IconItemUsbDelegate(){}

QSize IconItemUsbDelegate::sizeHint ( const QStyleOptionViewItem & /*option*/, const QModelIndex & index ) const
{
    // original method
    const QFileSystemModel *model = reinterpret_cast<const QFileSystemModel *>(index.model());
    QFileInfo info = model->fileInfo(index);
    if(info.isDir())
    {
        return QSize(40,40);
    }
    else
    {
        return QSize(64,64);
    }

//    // casting to proxy model then getting source model cast to QFileSystemModel
//    const USBDriveFilterProxyModel *proxymodel = reinterpret_cast<const USBDriveFilterProxyModel *>(index.model());
//    const QFileSystemModel *fsmodel = reinterpret_cast<const QFileSystemModel *>(proxymodel->sourceModel());
//    QFileInfo fsinfo = fsmodel->fileInfo(index);
//    if(fsinfo.isDir())
//    {
//        return QSize(40,40);
//    }
//    else
//    {
//        return QSize(64,64);
//    }

//    // no body, but just returning the same QSize every time.
//    return QSize(40,40);
}

QVariant IconFileSystemUsbModel::data ( const QModelIndex & index, int role ) const
{
    // will do more, but for now, just paints to view
    return QFileSystemModel::data(index, role);
}

FileSystemUsbModelDialog::FileSystemUsbModelDialog(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::FileSystemUsbModelWidget)
{
    ui->setupUi(this);

    dir = new IconFileSystemUsbModel();
    dir->setRootPath("\\");
    dir->setFilter(QDir::AllDirs | QDir::NoDotAndDotDot);

    usbModel = new USBDriveFilterProxyModel(this);
    usbModel->setSourceModel(dir);
    usbModel->setDynamicSortFilter(false);

    IconItemUsbDelegate *iconItemDelegate = new IconItemUsbDelegate();

    ui->treeView->setRootIsDecorated(false); // added
    ui->treeView->setModel(usbModel);
    ui->treeView->setSortingEnabled(true); // added
    //ui->treeView->setModel(dir); // changing to passing just the IconFileSystemUsbModel object works fine!!
    // hide unneeded hierachy info columns
    ui->treeView->hideColumn(1);
    ui->treeView->hideColumn(2);
    ui->treeView->hideColumn(3);
    ui->treeView->setItemDelegate(iconItemDelegate);
}

FileSystemUsbModelDialog::~FileSystemUsbModelDialog()
{
    delete dir;
}
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usbdrivefilter.h
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#ifndef USBDRIVEFILTER_H
#define USBDRIVEFILTER_H

#include <QSortFilterProxyModel>
#include <QModelIndex>
#include <QString>

class USBDriveFilterProxyModel : public QSortFilterProxyModel
{
    Q_OBJECT
public:
    explicit USBDriveFilterProxyModel(QObject *parent = 0);

protected:
    virtual bool filterAcceptsRow(
        int source_row, const QModelIndex &source_parent) const;

private:
    void getMountedRemovables();

private:
    QList<QString> removables;

};

#endif // USBDRIVEFILTER_H
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usbdrivefilter.cpp
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#include "usbdrivefilter.h"

#include <windows.h>

USBDriveFilterProxyModel::USBDriveFilterProxyModel(QObject *parent) :
    QSortFilterProxyModel(parent)
{
    getMountedRemovables();
    // will eventually also register for changes to mounted removables
    // but need to get passed my current issue of not displaying only USBs.
}

bool USBDriveFilterProxyModel::filterAcceptsRow(int sourceRow,
    const QModelIndex &sourceParent) const
{
    QModelIndex index0 = sourceModel()->index(sourceRow, 0, sourceParent);

    // Since drive string can have more than just "<DriveLetter>:", need
    // to check each entry in the usb list for whether it is contained in
    // the current drive string.

    QString source = sourceModel()->data(index0).toString();
    for (int i = 0; i < removables.size(); i++)
    {
        if (source.contains(removables[i]))
        {
            return true;
        }
    }
    return false;
}

void USBDriveFilterProxyModel::getMountedRemovables()
{
    DWORD test = GetLogicalDrives();

    DWORD mask = 1;
    UINT type = 0;
    WCHAR wdrive[] = L"C:\\"; // use as a drive letter template
    for (int i = 0; i < 32; i++)
    {
        if (test & mask)
        {
            wdrive[0] = (char)('A' + i); // change letter in template
            type = GetDriveType(wdrive);
            switch (type) {
            case DRIVE_REMOVABLE:
            {
                QString qdrive = QString((char)('A' + i)) + ":";
                removables.append(qdrive);
                break;
            }
            default: break;
            }
        }
        mask = mask << 1;
    }
}
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mainwindow.h
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#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class FileSystemUsbModelDialog;
class QFileSystemModel;

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;
    FileSystemUsbModelDialog *treeView;
    QFileSystemModel *fileSystemModel;
};

#endif // MAINWINDOW_H
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mainwindow.cpp
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#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "filesystemusbmodeldialog.h"

#include <QFileSystemModel>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    treeView = new FileSystemUsbModelDialog(this);
    setCentralWidget(treeView);
    fileSystemModel = new QFileSystemModel;
}

MainWindow::~MainWindow()
{
    delete ui;
}
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ui_filesystemusbmodelwidget.h
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/********************************************************************************
** Form generated from reading UI file 'filesystemmodelwidget.ui'
**
** Created by: Qt User Interface Compiler version 5.1.1
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/

#ifndef UI_FILESYSTEMUSBMODELWIDGET_H
#define UI_FILESYSTEMUSBMODELWIDGET_H

#include <QtWidgets/QApplication>
#include <QtWidgets/QHeaderView>
#include <QtWidgets/QTreeView>

QT_BEGIN_NAMESPACE

class Ui_FileSystemUsbModelWidget
{
public:
    QTreeView *treeView;

    void setupUi(QWidget *FileSystemUsbModelWidget)
    {
        if (FileSystemUsbModelWidget->objectName().isEmpty())
            FileSystemUsbModelWidget->setObjectName(QStringLiteral("FileSystemUsbModelWidget"));
        FileSystemUsbModelWidget->resize(670, 755);
        treeView = new QTreeView(FileSystemUsbModelWidget);
        treeView->setGeometry(QRect(0, 0, 670, 531));
        treeView->setObjectName(QStringLiteral("treeView"));
        treeView->setAutoFillBackground(true);
        treeView->setStyleSheet(QLatin1String(" QScrollBar:vertical {\n"
"      width: 61px;\n"
"       background-color: rgb(227, 227, 227);\n"
"  }\n"
"  QScrollBar::handle:vertical {\n"
"      min-height: 50px;\n"
"  }\n"
"\n"
"QTreeView, QListView {\n"
"       alternate-background-color: rgb(226, 226, 226);\n"
"       font-size: 16px;\n"
"     show-decoration-selected: 1;\n"
" }\n"
"\n"
" QTreeView::item, QListView::item {\n"
" height: 22px;\n"
"      border: 1px solid transparent;\n"
"     border-top-color: transparent;\n"
"     border-bottom-color: transparent;\n"
" }\n"
"\n"
" QTreeView::item:selected, QListView::item::selected {\n"
"     border: 1px solid #567dbc;\n"
"       background-color: rgb(85, 170, 255);\n"
" }\n"
"\n"
"\n"
" QTreeView::branch:has-siblings:!adjoins-item {\n"
"     border-image: url(:/new/prefix1/images/vline.png) 0;\n"
" }\n"
"\n"
" QTreeView::branch:has-siblings:adjoins-item {\n"
"     border-image: url(:/new/prefix1/images/branch-more.png) 0;\n"
" }\n"
"\n"
" QTreeView::branch:!has-children:!has-siblings:adjoins-item {\n"
"     border-image: url"
                        "(:/new/prefix1/images/branch-end.png) 0;\n"
" }\n"
"\n"
" QTreeView::branch:has-children:!has-siblings:closed,\n"
" QTreeView::branch:closed:has-children:has-siblings {\n"
"         border-image: none;\n"
"         image: url(:/new/prefix1/images/branch-closed.png);\n"
" }\n"
"\n"
" QTreeView::branch:open:has-children:!has-siblings,\n"
" QTreeView::branch:open:has-children:has-siblings  {\n"
"         border-image: none;\n"
"         image: url(:/new/prefix1/images/branch-open.png);\n"
" }\n"
""));
        treeView->setFrameShape(QFrame::Box);
        treeView->setFrameShadow(QFrame::Plain);
        treeView->setHorizontalScrollMode(QAbstractItemView::ScrollPerItem);
        treeView->setExpandsOnDoubleClick(true);
        treeView->header()->setVisible(false);
        treeView->header()->setStretchLastSection(true);

        retranslateUi(FileSystemUsbModelWidget);

        QMetaObject::connectSlotsByName(FileSystemUsbModelWidget);
    } // setupUi

    void retranslateUi(QWidget *FileSystemUsbModelWidget)
    {
        FileSystemUsbModelWidget->setWindowTitle(QApplication::translate("FileSystemUsbModelWidget", "Form", 0));
    } // retranslateUi

};

namespace Ui {
    class FileSystemUsbModelWidget: public Ui_FileSystemUsbModelWidget {};
} // namespace Ui

QT_END_NAMESPACE

#endif // UI_FILESYSTEMMODELWIDGET_H
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