sqlitebrowser/src/ExtendedTableWidget.cpp

#include "ExtendedTableWidget.h"
#include "sqlitetablemodel.h"
#include "FilterTableHeader.h"
#include "sqlitetypes.h"
#include "Settings.h"

#include <QApplication>
#include <QClipboard>
#include <QMimeData>
#include <QKeySequence>
#include <QKeyEvent>
#include <QScrollBar>
#include <QHeaderView>
#include <QMessageBox>
#include <QBuffer>
#include <QMenu>
#include <QDateTime>
#include <QLineEdit>
#include <limits>

#if QT_VERSION < QT_VERSION_CHECK(5, 4, 0)
    typedef QList<QByteArray> QByteArrayList;
#endif

QList<QByteArrayList> ExtendedTableWidget::m_buffer;
QString ExtendedTableWidget::m_generatorStamp;

namespace
{

QList<QByteArrayList> parseClipboard(QString clipboard)
{
    // Remove trailing line break from the clipboard text. This is necessary because some applications append an extra
    // line break to the clipboard contents which we would then interpret as regular data, setting the first field of the
    // first row after the paste area to NULL. One problem here is that this breaks for those cases where an empty line at
    // the end of the selection is explicitly copied and the originating application doesn't add an extra line break. However,
    // there are two reasons for favoring this way: 1) Spreadsheet applications seem to add an extra line break and they are
    // probably the main source for pasted data, 2) Having to manually delete on extra field seems to be less problematic than
    // having one extra field deleted without any warning.
    if(clipboard.endsWith("\n"))
        clipboard.chop(1);
    if(clipboard.endsWith("\r"))
        clipboard.chop(1);

    // Make sure there is some data in the clipboard
    QList<QByteArrayList> result;
    if(clipboard.isEmpty())
        return result;

    result.push_back(QByteArrayList());

    QRegExp re("(\"(?:[^\t\"]+|\"\"[^\"]*\"\")*)\"|(\t|\r?\n)");
    int offset = 0;
    int whitespace_offset = 0;

    while (offset >= 0) {
        QString text;
        int pos = re.indexIn(clipboard, offset);
        if (pos < 0) {
            // insert everything that left
            text = clipboard.mid(whitespace_offset);
            if(QRegExp("\".*\"").exactMatch(text))
                text = text.mid(1, text.length() - 2);
            text.replace("\"\"", "\"");
            result.last().push_back(text.toUtf8());
            break;
        }

        if (re.pos(2) < 0) {
            offset = pos + re.cap(1).length() + 1;
            continue;
        }

        QString ws = re.cap(2);
        // if two whitespaces in row - that's an empty cell
        if (!(pos - whitespace_offset)) {
            result.last().push_back(QByteArray());
        } else {
            text = clipboard.mid(whitespace_offset, pos - whitespace_offset);
            if(QRegExp("\".*\"").exactMatch(text))
                text = text.mid(1, text.length() - 2);
            text.replace("\"\"", "\"");
            result.last().push_back(text.toUtf8());
        }

        if (ws.endsWith("\n"))
            // create new row
            result.push_back(QByteArrayList());

        whitespace_offset = offset = pos + ws.length();
    }

    return result;
}

}


ExtendedTableWidgetEditorDelegate::ExtendedTableWidgetEditorDelegate(QObject* parent)
    : QStyledItemDelegate(parent)
{
}

QWidget* ExtendedTableWidgetEditorDelegate::createEditor(QWidget* parent, const QStyleOptionViewItem& /*option*/, const QModelIndex& /*index*/) const
{
    // Just create a normal line editor but set the maximum length to the highest possible value instead of the default 32768.
    QLineEdit* editor = new QLineEdit(parent);
    editor->setMaxLength(std::numeric_limits<int>::max());
    return editor;
}

void ExtendedTableWidgetEditorDelegate::setEditorData(QWidget* editor, const QModelIndex& index) const
{
    QLineEdit* lineedit = static_cast<QLineEdit*>(editor);

    // Set the data for the line editor
    QString data = index.data(Qt::EditRole).toString();
    lineedit->setText(data);

    // Put the editor in read only mode if the actual data is larger than the maximum length to avoid accidental truncation of the data
    lineedit->setReadOnly(data.size() > lineedit->maxLength());
}

void ExtendedTableWidgetEditorDelegate::setModelData(QWidget* editor, QAbstractItemModel* model, const QModelIndex& index) const
{
    // Only apply the data back to the model if the editor is not in read only mode to avoid accidental truncation of the data
    QLineEdit* lineedit = static_cast<QLineEdit*>(editor);
    if(!lineedit->isReadOnly())
        model->setData(index, lineedit->text());
}

void ExtendedTableWidgetEditorDelegate::updateEditorGeometry(QWidget* editor, const QStyleOptionViewItem& option, const QModelIndex& /*index*/) const
{
    editor->setGeometry(option.rect);
}


ExtendedTableWidget::ExtendedTableWidget(QWidget* parent) :
    QTableView(parent)
{
    setHorizontalScrollMode(ExtendedTableWidget::ScrollPerPixel);
    // Force ScrollPerItem, so scrolling shows all table rows
    setVerticalScrollMode(ExtendedTableWidget::ScrollPerItem);

    connect(verticalScrollBar(), SIGNAL(valueChanged(int)), this, SLOT(vscrollbarChanged(int)));
    connect(this, SIGNAL(clicked(QModelIndex)), this, SLOT(cellClicked(QModelIndex)));

    // Set up filter row
    m_tableHeader = new FilterTableHeader(this);
    setHorizontalHeader(m_tableHeader);

    // Set up vertical header context menu
    verticalHeader()->setContextMenuPolicy(Qt::CustomContextMenu);

    // Set up table view context menu
    m_contextMenu = new QMenu(this);

    QAction* filterAction = new QAction(tr("Use as Exact Filter"), m_contextMenu);
    QAction* containingAction = new QAction(tr("Containing"), m_contextMenu);
    QAction* notEqualToAction = new QAction(tr("Not equal to"), m_contextMenu);
    QAction* greaterThanAction = new QAction(tr("Greater than"), m_contextMenu);
    QAction* lessThanAction = new QAction(tr("Less than"), m_contextMenu);
    QAction* greaterEqualAction = new QAction(tr("Greater or equal"), m_contextMenu);
    QAction* lessEqualAction = new QAction(tr("Less or equal"), m_contextMenu);
    QAction* inRangeAction = new QAction(tr("Between this and..."), m_contextMenu);

    QAction* nullAction = new QAction(tr("Set to NULL"), m_contextMenu);
    QAction* copyAction = new QAction(QIcon(":/icons/copy"), tr("Copy"), m_contextMenu);
    QAction* copyWithHeadersAction = new QAction(QIcon(":/icons/special_copy"), tr("Copy with Headers"), m_contextMenu);
    QAction* copyAsSQLAction = new QAction(QIcon(":/icons/sql_copy"), tr("Copy as SQL"), m_contextMenu);
    QAction* pasteAction = new QAction(QIcon(":/icons/paste"), tr("Paste"), m_contextMenu);

    m_contextMenu->addAction(filterAction);
    QMenu* filterMenu = m_contextMenu->addMenu(tr("Use in Filter Expression"));
    filterMenu->addAction(containingAction);
    filterMenu->addAction(notEqualToAction);
    filterMenu->addAction(greaterThanAction);
    filterMenu->addAction(lessThanAction);
    filterMenu->addAction(greaterEqualAction);
    filterMenu->addAction(lessEqualAction);
    filterMenu->addAction(inRangeAction);

    m_contextMenu->addSeparator();
    m_contextMenu->addAction(nullAction);
    m_contextMenu->addSeparator();
    m_contextMenu->addAction(copyAction);
    m_contextMenu->addAction(copyWithHeadersAction);
    m_contextMenu->addAction(copyAsSQLAction);
    m_contextMenu->addAction(pasteAction);
    setContextMenuPolicy(Qt::CustomContextMenu);

    // Create and set up delegate
    m_editorDelegate = new ExtendedTableWidgetEditorDelegate(this);
    setItemDelegate(m_editorDelegate);

    // This is only for displaying the shortcut in the context menu.
    // An entry in keyPressEvent is still needed.
    nullAction->setShortcut(QKeySequence(tr("Alt+Del")));
    copyAction->setShortcut(QKeySequence::Copy);
    copyWithHeadersAction->setShortcut(QKeySequence(tr("Ctrl+Shift+C")));
    copyAsSQLAction->setShortcut(QKeySequence(tr("Ctrl+Alt+C")));
    pasteAction->setShortcut(QKeySequence::Paste);

    // Set up context menu actions
    connect(this, &QTableView::customContextMenuRequested,
            [=](const QPoint& pos)
    {
        // Deactivate context menu options if there is no model set
        bool enabled = model();
        filterAction->setEnabled(enabled);
        filterMenu->setEnabled(enabled);
        copyAction->setEnabled(enabled);
        copyWithHeadersAction->setEnabled(enabled);
        copyAsSQLAction->setEnabled(enabled);

        // Hide filter actions when there isn't any filters
        bool hasFilters = m_tableHeader->hasFilters();
        filterAction->setVisible(hasFilters);
        filterMenu->menuAction()->setVisible(hasFilters);

        // Try to find out whether the current view is editable and (de)activate menu options according to that
        bool editable = editTriggers() != QAbstractItemView::NoEditTriggers;
        nullAction->setEnabled(enabled && editable);
        pasteAction->setEnabled(enabled && editable);

        // Show menu
        m_contextMenu->popup(viewport()->mapToGlobal(pos));
    });
    connect(filterAction, &QAction::triggered, [&]() {
        useAsFilter(QString ("="));
    });
    connect(containingAction, &QAction::triggered, [&]() {
            useAsFilter(QString (""));
        });
    connect(notEqualToAction, &QAction::triggered, [&]() {
            useAsFilter(QString ("<>"));
        });
    connect(greaterThanAction, &QAction::triggered, [&]() {
            useAsFilter(QString (">"));
        });
    connect(lessThanAction, &QAction::triggered, [&]() {
            useAsFilter(QString ("<"));
        });
    connect(greaterEqualAction, &QAction::triggered, [&]() {
            useAsFilter(QString (">="));
        });
    connect(lessEqualAction, &QAction::triggered, [&]() {
            useAsFilter(QString ("<="));
        });
    connect(inRangeAction, &QAction::triggered, [&]() {
            useAsFilter(QString ("~"), /* binary */ true);
        });

    connect(nullAction, &QAction::triggered, [&]() {
        for(const QModelIndex& index : selectedIndexes())
            model()->setData(index, QVariant());
    });
    connect(copyAction, &QAction::triggered, [&]() {
       copy(false, false);
    });
    connect(copyWithHeadersAction, &QAction::triggered, [&]() {
       copy(true, false);
    });
    connect(copyAsSQLAction, &QAction::triggered, [&]() {
       copy(false, true);
    });
    connect(pasteAction, &QAction::triggered, [&]() {
       paste();
    });
}

void ExtendedTableWidget::reloadSettings()
{
    // Set the new font and font size
    QFont dataBrowserFont(Settings::getValue("databrowser", "font").toString());
    dataBrowserFont.setPointSize(Settings::getValue("databrowser", "fontsize").toInt());
    setFont(dataBrowserFont);

    // Set new default row height depending on the font size
    verticalHeader()->setDefaultSectionSize(verticalHeader()->fontMetrics().height()+10);
}

void ExtendedTableWidget::copy(const bool withHeaders, const bool inSQL )
{
    QModelIndexList indices = selectionModel()->selectedIndexes();

    // Remove all indices from hidden columns, because if we don't we might copy data from hidden columns as well which is very
    // unintuitive; especially copying the rowid column when selecting all columns of a table is a problem because pasting the data
    // won't work as expected.
    QMutableListIterator<QModelIndex> i(indices);
    while (i.hasNext()) {
        if (isColumnHidden(i.next().column()))
            i.remove();
    }

    // Abort if there's nothing to copy
    if (indices.isEmpty())
        return;

    SqliteTableModel* m = qobject_cast<SqliteTableModel*>(model());

    // Clear internal copy-paste buffer
    m_buffer.clear();

    // If a single cell is selected, copy it to clipboard
    if (!inSQL && !withHeaders && indices.size() == 1) {
        QImage img;
        QVariant data = m->data(indices.first(), Qt::EditRole);

        if (img.loadFromData(data.toByteArray()))
        {
            // If it's an image, copy the image data to the clipboard
            qApp->clipboard()->setImage(img);
            return;
        } else {
            // It it's not an image, check if it's an empty field
            if (data.toByteArray().isEmpty())
            {
                // The field is either NULL or empty. Those are are handled via the internal copy-paste buffer
                qApp->clipboard()->setText(QString());      // Calling clear() alone doesn't seem to work on all systems
                qApp->clipboard()->clear();
                m_buffer.push_back(QByteArrayList{data.toByteArray()});
                return;
            }

            // The field isn't empty. Copy the text to the clipboard without quoting (for general plain text clipboard)
            qApp->clipboard()->setText(data.toByteArray());
            return;
        }
    }

    // If we got here, there are multiple selected cells, or copy with headers was requested.
    // In this case, we copy selected data into internal copy-paste buffer and then
    // we write a table both in HTML and text formats to the system clipboard.

    // Copy selected data into internal copy-paste buffer
    int last_row = indices.first().row();
    QByteArrayList lst;
    for(int i=0;i<indices.size();i++)
    {
        if(indices.at(i).row() != last_row)
        {
            m_buffer.push_back(lst);
            lst.clear();
        }
        lst << indices.at(i).data(Qt::EditRole).toByteArray();
        last_row = indices.at(i).row();
    }
    m_buffer.push_back(lst);

    QString sqlResult;
    QString result;
    QString htmlResult = "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">";
    htmlResult.append("<html><head><meta http-equiv=\"content-type\" content=\"text/html; charset=utf-8\">");
    htmlResult.append("<title></title>");

    // The generator-stamp is later used to know whether the data in the system clipboard is still ours.
    // In that case we will give precedence to our internal copy buffer.
    QString now = QDateTime::currentDateTime().toString("YYYY-MM-DDTHH:mm:ss.zzz");
    m_generatorStamp = QString("<meta name=\"generator\" content=\"%1\"><meta name=\"date\" content=\"%2\">").arg(QApplication::applicationName().toHtmlEscaped(), now);
    htmlResult.append(m_generatorStamp);
    // TODO: is this really needed by Excel, since we use <pre> for multi-line cells?
    htmlResult.append("<style type=\"text/css\">br{mso-data-placement:same-cell;}</style></head><body><table>");

    int currentRow = indices.first().row();

    const QString fieldSepHtml = "</td><td>";
    const QString rowSepHtml = "</td></tr><tr><td>";
    const QString fieldSepText = "\t";
#ifdef Q_OS_WIN
    const QString rowSepText = "\r\n";
#else
    const QString rowSepText = "\n";
#endif

    QString sqlInsertStatement = QString("INSERT INTO %1 (").arg(m->currentTableName().toString());
    // Table headers
    if (withHeaders || inSQL) {
        htmlResult.append("<tr><th>");
        int firstColumn = indices.front().column();
        for(int i = firstColumn; i <= indices.back().column(); i++) {
            QByteArray headerText = model()->headerData(i, Qt::Horizontal, Qt::DisplayRole).toByteArray();
            if (i != firstColumn) {
                result.append(fieldSepText);
                htmlResult.append("</th><th>");
                sqlInsertStatement.append(", ");
            }

            result.append(escapeCopiedData(headerText));
            htmlResult.append(headerText);
            sqlInsertStatement.append(sqlb::escapeIdentifier(headerText));
        }
        result.append(rowSepText);
        htmlResult.append("</th></tr>");
        sqlInsertStatement.append(") VALUES (");
    }

    // Table data rows
    for(const QModelIndex& index : indices) {
        // Separators. For first cell, only opening table row tags must be added for the HTML and nothing for the text version.
        if (indices.first() == index) {
            htmlResult.append("<tr><td>");
            sqlResult.append(sqlInsertStatement);
        } else if (index.row() != currentRow) {
            result.append(rowSepText);
            htmlResult.append(rowSepHtml);
            sqlResult.append(");" + rowSepText + sqlInsertStatement);
        } else {
            result.append(fieldSepText);
            htmlResult.append(fieldSepHtml);
            sqlResult.append(", ");
        }
        currentRow = index.row();

        QImage img;
        QVariant data = index.data(Qt::EditRole);

        // Table cell data: image? Store it as an embedded image in HTML
        if (!inSQL && img.loadFromData(data.toByteArray()))
        {
            QByteArray ba;
            QBuffer buffer(&ba);
            buffer.open(QIODevice::WriteOnly);
            img.save(&buffer, "PNG");
            buffer.close();

            QString imageBase64 = ba.toBase64();
            htmlResult.append("<img src=\"data:image/png;base64,");
            htmlResult.append(imageBase64);
            result.append(QString());
            htmlResult.append("\" alt=\"Image\">");
        } else {
            QByteArray text;
            if (!m->isBinary(index)) {
                text = data.toByteArray();

                // Table cell data: text
                if (text.contains('\n') || text.contains('\t'))
                    htmlResult.append("<pre>" + QString(text).toHtmlEscaped() + "</pre>");
                else
                    htmlResult.append(QString(text).toHtmlEscaped());

                result.append(escapeCopiedData(text));
                sqlResult.append("'" + text.replace("'", "''") + "'");
            } else
                // Table cell data: binary. Save as BLOB literal in SQL
                sqlResult.append( "X'" + data.toByteArray().toHex() + "'" );

        }
    }
    sqlResult.append(");");

    QMimeData *mimeData = new QMimeData;
    if ( inSQL )
    {
        mimeData->setText(sqlResult);
    } else {
        mimeData->setHtml(htmlResult + "</td></tr></table></body></html>");
        mimeData->setText(result);
    }
    qApp->clipboard()->setMimeData(mimeData);
}

QString ExtendedTableWidget::escapeCopiedData(const QByteArray& data) const
{
    // Empty string is enquoted in plain text format, whilst NULL isn't
    // We also quote the data when there are line breaks in the text, again for spreadsheet compatability.
    // We also need to quote when there are tabs in the string (another option would be to replace the tabs by spaces, that's what
    // LibreOffice seems to be doing here).

    if(data.isNull())
        return data;

    QString text = data;
    if(text.isEmpty() || text.contains('\n') || text.contains('\t') || text.contains('"'))
    {
        text.replace("\"", "\"\"");
        return QString("\"%1\"").arg(text);
    } else {
        return text;
    }
}

void ExtendedTableWidget::paste()
{
    // Get list of selected items
    QItemSelectionModel* selection = selectionModel();
    QModelIndexList indices = selection->selectedIndexes();

    // Abort if there's nowhere to paste
    if(indices.isEmpty())
        return;

    SqliteTableModel* m = qobject_cast<SqliteTableModel*>(model());

    // We're also checking for system clipboard data first. Only if the data in the system clipboard is not ours, we use the system
    // clipboard, otherwise we prefer the internal buffer.  That's because the data in the internal buffer is easier to parse and more
    // accurate, too. However, if we always preferred the internal copy-paste buffer there would be no way to copy data from other
    // applications in here once the internal buffer has been filled.

    // If clipboard contains an image and no text, just insert the image
    const QMimeData* mimeClipboard = qApp->clipboard()->mimeData();
    if (mimeClipboard->hasImage() && !mimeClipboard->hasText()) {
        QImage img = qApp->clipboard()->image();
        QByteArray ba;
        QBuffer buffer(&ba);
        buffer.open(QIODevice::WriteOnly);
        img.save(&buffer, "PNG");       // We're always converting the image format to PNG here. TODO: Is that correct?
        buffer.close();

        m->setData(indices.first(), ba);
        return;
    }

    // Get the clipboard text
    QString clipboard = qApp->clipboard()->text();


    // If data in system clipboard is ours and the internal copy-paste buffer is filled, use the internal buffer; otherwise parse the
    // system clipboard contents (case for data copied by other application).

    QList<QByteArrayList> clipboardTable;
    QList<QByteArrayList>* source;

    if(mimeClipboard->hasHtml() && mimeClipboard->html().contains(m_generatorStamp) && !m_buffer.isEmpty())
    {
        source = &m_buffer;
    } else {
        clipboardTable = parseClipboard(clipboard);
        source = &clipboardTable;
    }

    // Stop here if there's nothing to paste
    if(!source->size())
        return;

    // Starting from assumption that selection is rectangular, and then first index is upper-left corner and last is lower-right.
    int rows = source->size();
    int columns = source->first().size();

    int firstRow = indices.front().row();
    int firstColumn = indices.front().column();
    int selectedRows = indices.back().row() - firstRow + 1;
    int selectedColumns = indices.back().column() - firstColumn + 1;

    // If last row and column are after table size, clamp it
    int lastRow = qMin(firstRow + rows - 1, m->rowCount() - 1);
    int lastColumn = qMin(firstColumn + columns - 1, m->columnCount() - 1);

    // Special case: if there is only one cell of data to be pasted, paste it into all selected fields
    if(rows == 1 && columns == 1)
    {
        QByteArray data = source->first().first();
        for(int row=firstRow;row<firstRow+selectedRows;row++)
        {
            for(int column=firstColumn;column<firstColumn+selectedColumns;column++)
                m->setData(m->index(row, column), data);
        }
        return;
    }

    // If more than one cell was selected, check if the selection matches the cliboard dimensions
    if(selectedRows != rows || selectedColumns != columns)
    {
        // Ask user if they are sure about this
        if(QMessageBox::question(this, QApplication::applicationName(),
                                 tr("The content of the clipboard is bigger than the range selected.\nDo you want to insert it anyway?"),
                                 QMessageBox::Yes | QMessageBox::No) != QMessageBox::Yes)
        {
            // If the user doesn't want to paste the clipboard data anymore, stop now
            return;
        }
    }

    // If we get here, we can definitely start pasting: either the ranges match in their size or the user agreed to paste anyway

    // Copy the data cell by cell and as-is from the source buffer to the table
    int row = firstRow;
    for(const QByteArrayList& source_row : *source)
    {
        int column = firstColumn;
        for(const QByteArray& source_cell : source_row)
        {
            m->setData(m->index(row, column), source_cell);

            column++;
            if (column > lastColumn)
                break;
        }

        row++;
        if (row > lastRow)
            break;
    }
}

void ExtendedTableWidget::useAsFilter(const QString& filterOperator, bool binary)
{
    QModelIndex index = selectionModel()->currentIndex();
    SqliteTableModel* m = qobject_cast<SqliteTableModel*>(model());

    // Abort if there's nothing to filter
    if (!index.isValid() || !selectionModel()->hasSelection() || m->isBinary(index))
        return;

    QVariant data = model()->data(index, Qt::EditRole);
    QString value;
    if (data.isNull())
        value = "NULL";
    else if (data.toString().isEmpty())
        value = "''";
    else
        value = data.toString();

    // When Containing filter is requested (empty operator) and the value starts with
    // an operator character, the character is escaped.
    if (filterOperator.isEmpty())
        value.replace(QRegExp("^(<|>|=)"), Settings::getValue("databrowser", "filter_escape").toString() + QString("\\1"));

    // If binary operator, the cell data is used as first value and
    // the second value must be added by the user.
    if (binary)
        m_tableHeader->setFilter(index.column(), value + filterOperator);
    else
        m_tableHeader->setFilter(index.column(), filterOperator + value);
}

void ExtendedTableWidget::keyPressEvent(QKeyEvent* event)
{
    // Call a custom copy method when Ctrl-C is pressed
    if(event->matches(QKeySequence::Copy))
    {
        copy(false, false);
        return;
    } else if(event->matches(QKeySequence::Paste)) {
        // Call a custom paste method when Ctrl-V is pressed
        paste();
    } else if(event->modifiers().testFlag(Qt::ControlModifier) && event->modifiers().testFlag(Qt::ShiftModifier) && (event->key() == Qt::Key_C)) {
        // Call copy with headers when Ctrl-Shift-C is pressed
        copy(true, false);
    } else if(event->modifiers().testFlag(Qt::ControlModifier) && event->modifiers().testFlag(Qt::AltModifier) && (event->key() == Qt::Key_C)) {
        // Call copy in SQL format when Ctrl-Alt-C is pressed
        copy(false, true);
    } else if(event->key() == Qt::Key_Tab && hasFocus() &&
              selectedIndexes().count() == 1 &&
              selectedIndexes().at(0).row() == model()->rowCount()-1 && selectedIndexes().at(0).column() == model()->columnCount()-1) {
        // If the Tab key was pressed while the focus was on the last cell of the last row insert a new row automatically
        model()->insertRow(model()->rowCount());
    } else if ((event->key() == Qt::Key_Delete) || (event->key() == Qt::Key_Backspace)) {
        // Check if entire rows are selected. We call the selectedRows() method here not only for simplicity reasons but also because it distinguishes between
        // "an entire row is selected" and "all cells of a row are selected", the former is e.g. the case when the row number is clicked, the latter when all cells
        // are selected manually. This is an important distinction (especially when a table has only one column!) to match the users' expectations. Also never
        // delete records when the backspace key was pressed.
        if(event->key() == Qt::Key_Delete && selectionModel()->selectedRows().size())
        {
            // At least on entire row is selected. Because we don't allow completely arbitrary selections (at least at the moment) but only block selections,
            // this means that only entire entire rows are selected. If an entire row is (or multiple entire rows are) selected, we delete that record instead
            // of deleting only the cell contents.

            emit selectedRowsToBeDeleted();
        } else {
            // No entire row is selected. So just set the selected cells to null or empty string depending on the modifier keys

            if(event->modifiers().testFlag(Qt::AltModifier))
            {
                // When pressing Alt+Delete set the value to NULL
                for(const QModelIndex& index : selectedIndexes())
                    model()->setData(index, QVariant());
            } else {
                // When pressing Delete only set the value to empty string
                for(const QModelIndex& index : selectedIndexes())
                    model()->setData(index, "");
            }
        }
    } else if(event->modifiers().testFlag(Qt::ControlModifier) && (event->key() == Qt::Key_PageUp || event->key() == Qt::Key_PageDown)) {
        // When pressing Ctrl + Page up/down send a signal indicating the user wants to change the current table
        emit switchTable(event->key() == Qt::Key_PageDown);
        return;
    }

    // This prevents the current selection from being changed when pressing tab to move to the next filter. Note that this is in an 'if' condition,
    // not in an 'else if' because this way, when the tab key was pressed and the focus was on the last cell, a new row is inserted and then the tab
    // key press is processed a second time to move the cursor as well
    if((event->key() != Qt::Key_Tab && event->key() != Qt::Key_Backtab) || hasFocus())
        QTableView::keyPressEvent(event);
}

void ExtendedTableWidget::updateGeometries()
{
    // Call the parent implementation first - it does most of the actual logic
    QTableView::updateGeometries();

    // Check if a model has already been set yet
    if(model())
    {
        // If so and if it is a SqliteTableModel and if the parent implementation of this method decided that a scrollbar is needed, update its maximum value
        SqliteTableModel* m = qobject_cast<SqliteTableModel*>(model());
        if(m && verticalScrollBar()->maximum())
            verticalScrollBar()->setMaximum(m->rowCount() - numVisibleRows() + 1);
    }
}

void ExtendedTableWidget::vscrollbarChanged(int value)
{
    // Cancel if there is no model set yet - this shouldn't happen (because without a model there should be no scrollbar) but just to be sure...
    if(!model())
        return;

    // Fetch more data from the DB if necessary
    const auto nrows = model()->rowCount();
    if(nrows == 0)
        return;

    if(auto * m = dynamic_cast<SqliteTableModel*>(model()))
    {
        int row_begin = std::min(value, nrows - 1);
        int row_end = std::min(value + numVisibleRows(), nrows);
        m->triggerCacheLoad(row_begin, row_end);
    }
}

int ExtendedTableWidget::numVisibleRows()
{
    // Get the row numbers of the rows currently visible at the top and the bottom of the widget
    int row_top = rowAt(0) == -1 ? 0 : rowAt(0);
    int row_bottom = rowAt(height()) == -1 ? model()->rowCount() : rowAt(height());

    // Calculate the number of visible rows
    return row_bottom - row_top;
}

QSet<int> ExtendedTableWidget::selectedCols()
{
    QSet<int> selectedCols;
    for(const QModelIndex & idx : selectedIndexes())
        selectedCols.insert(idx.column());
    return selectedCols;
}

void ExtendedTableWidget::cellClicked(const QModelIndex& index)
{
    // If Ctrl-Shift is pressed try to jump to the row referenced by the foreign key of the clicked cell
    if(qApp->keyboardModifiers().testFlag(Qt::ControlModifier) && qApp->keyboardModifiers().testFlag(Qt::ShiftModifier) && model())
    {
        SqliteTableModel* m = qobject_cast<SqliteTableModel*>(model());
        sqlb::ForeignKeyClause fk = m->getForeignKeyClause(index.column()-1);

        if(fk.isSet())
            emit foreignKeyClicked(sqlb::ObjectIdentifier(m->currentTableName().schema(), fk.table()),
                                   fk.columns().size() ? fk.columns().at(0) : "",
                                   m->data(index, Qt::EditRole).toByteArray());
    }
}

void ExtendedTableWidget::dragEnterEvent(QDragEnterEvent* event)
{
    event->accept();
}

void ExtendedTableWidget::dragMoveEvent(QDragMoveEvent* event)
{
    event->accept();
}

void ExtendedTableWidget::dropEvent(QDropEvent* event)
{
    QModelIndex index = indexAt(event->pos());

    if (!index.isValid())
    {
        if (event->mimeData()->hasUrls() && event->mimeData()->urls().first().isLocalFile())
            emit openFileFromDropEvent(event->mimeData()->urls().first().toLocalFile());
        return;
    }

    model()->dropMimeData(event->mimeData(), Qt::CopyAction, index.row(), index.column(), QModelIndex());
    event->acceptProposedAction();
}

void ExtendedTableWidget::selectTableLine(int lineToSelect)
{
    SqliteTableModel* m = qobject_cast<SqliteTableModel*>(model());

    // Are there even that many lines?
    if(lineToSelect >= m->rowCount())
        return;

    QApplication::setOverrideCursor( Qt::WaitCursor );
    m->triggerCacheLoad(lineToSelect);

    // Select it
    clearSelection();
    selectRow(lineToSelect);
    scrollTo(currentIndex(), QAbstractItemView::PositionAtTop);
    QApplication::restoreOverrideCursor();
}

void ExtendedTableWidget::selectTableLines(int firstLine, int count)
{
    SqliteTableModel* m = qobject_cast<SqliteTableModel*>(model());

    int lastLine = firstLine+count-1;
    // Are there even that many lines?
    if(lastLine >= m->rowCount())
        return;

    selectTableLine(firstLine);

    QModelIndex topLeft = m->index(firstLine, 0);
    QModelIndex bottomRight = m->index(lastLine, m->columnCount()-1);

    selectionModel()->select(QItemSelection(topLeft, bottomRight), QItemSelectionModel::Select | QItemSelectionModel::Rows);
}