I was facing the exact same issue, though with a custom delegate inside a QTableView which has a QPlainTextEdit as editor. Initailly, the editor would not grow beyond the size of its table cell.
What did not work for me:
updateEditorGeometry(): was only called on initial show()- custom
sizeHint(): wasn't called ever, neither in subclass or baseclass, regardless any update(), updateGeometry() calls or signals
After seemingly endless hours of collecting small chunks of info about some undocumented QPlainTextEdit/QTextDocument 'features' and Qt quirks I got what I want by connecting to QPlainTextEdit->document()->documentLayout()'s documentSizeChanged(QSizeF) signal.
Below are the essentials to expand the editor as desired while limiting it to the parent QTableView's viewport (m_pTableView).
Hope this makes sense to anyone. Example code is not compilable as is but should give enough hints to get started.
h editor + delegate
#include <QPlainTextEdit>
// A custom QStyledItemDelegate
#include "library/tableitemdelegate.h"
/// A QPlainTextEdit to show all content lines in a scrollable view.
/// * finish editing with Return (like QLineEdit used for other metadata)
/// * add new line with Shift+Return.
/// Horizontal scrollbar is hidden as long as content is just one line.
/// Note: QTextEdit is no option here since it seems to transform content with
/// line breaks to html doc when committing data.
class MultiLineEditor : public QPlainTextEdit {
Q_OBJECT
public:
MultiLineEditor(QWidget* pParent);
bool eventFilter(QObject* obj, QEvent* event) override;
signals:
void editingFinished();
};
class MultiLineEditDelegate : public TableItemDelegate {
Q_OBJECT
public:
explicit MultiLineEditDelegate(QTableView* pTrackTable);
~MultiLineEditDelegate() override = default;
// called when the user starts editing an item
QWidget* createEditor(QWidget* parent,
const QStyleOptionViewItem& option,
const QModelIndex& index) const override;
private slots:
void commitAndCloseEditor();
private:
void adjustEditor(MultiLineEditor* pEditor, const QSizeF size) const;
mutable QRect m_editRect;
mutable int m_lineCount;
};
cpp editor + delegate
#include "library/multilineeditdelegate.h"
#include <QAbstractTextDocumentLayout>
#include <cmath>
#include "moc_multilineeditdelegate.cpp"
MultiLineEditor::MultiLineEditor(QWidget* pParent)
: QPlainTextEdit(pParent) {
setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::MinimumExpanding);
// Disable line wrap for a predictable view (like QLineEdit).
// Horizontal scrollbars show up automatically.
setLineWrapMode(QPlainTextEdit::NoWrap);
// Remove ugly content offset, most notable with one-liners
setContentsMargins(0, 0, 0, 0);
document()->setDocumentMargin(0);
// Add event filter to catch right-clicks and key presses
installEventFilter(this);
};
bool MultiLineEditor::eventFilter(QObject* obj, QEvent* event) {
if (event->type() == QEvent::MouseButtonPress) {
// Work around a strange quirk: right-clicks outside the rectangle of
// the underlying table index are not triggering the context menu.
// Simply returning true fixes it.
QMouseEvent* me = static_cast<QMouseEvent*>(event);
if (me->button() == Qt::RightButton &&
rect().contains(me->pos(), false)) {
return true;
}
} else if (event->type() == QEvent::KeyPress) {
// Finish editing with Return key like in QLineEdit
QKeyEvent* ke = static_cast<QKeyEvent*>(event);
if ((ke->key() == Qt::Key_Return || ke->key() == Qt::Key_Enter) &&
ke->modifiers().testFlag(Qt::NoModifier)) {
emit editingFinished();
return false;
}
}
return QPlainTextEdit::eventFilter(obj, event);
}
MultiLineEditDelegate::MultiLineEditDelegate(QTableView* pTableView)
: TableItemDelegate(pTableView),
m_lineCount(0) {
}
QWidget* MultiLineEditDelegate::createEditor(QWidget* pParent,
const QStyleOptionViewItem& option,
const QModelIndex& index) const {
Q_UNUSED(index);
auto* pEditor = new MultiLineEditor(pParent);
auto* pDocLayout = pEditor->document()->documentLayout();
// Adjust height to fit content and maybe shift vertically to fit into the
// library view. documentSizeChanged() is emitted when text changed, incl.
// initial fill.
// We could also connect to QPlainTextEdit::blockCountChanged(), though
// for some reason, that only works for documents with 2+ lines
// appending line breaks to single-line docs won't fire that signal :|
connect(pDocLayout,
&QAbstractTextDocumentLayout::documentSizeChanged,
this,
[this, pEditor](const QSizeF size) {
adjustEditor(pEditor, size);
});
// emitted when pressing Return key to act like QLineEdit
connect(pEditor,
&MultiLineEditor::editingFinished,
this,
&MultiLineEditDelegate::commitAndCloseEditor);
// Store the initial rectangle so we can read the x/y origin and in adjustEditor()
m_editRect = option.rect;
return pEditor;
}
void MultiLineEditDelegate::adjustEditor(MultiLineEditor* pEditor, const QSizeF size) const {
// Compared to QTextEdit, size.height() is the line count (Qt speak: blocks)
int newLineCount = static_cast<int>(round(size.height()));
// Only act if line count changed
if (newLineCount == m_lineCount) {
return;
} else {
m_lineCount = newLineCount;
}
// Remove the scrollbars if content is just one line to emulate QLineEdit
// appearace, else enable auto mode.
Qt::ScrollBarPolicy pol(m_lineCount > 1 ? Qt::ScrollBarAsNeeded : Qt::ScrollBarAlwaysOff);
pEditor->setVerticalScrollBarPolicy(pol);
pEditor->setHorizontalScrollBarPolicy(pol);
// Calculate the content height
int lines = m_lineCount;
// Add extra margin so the horizontal scrollbar doesn't obstruct the last
// line (which also avoids the vertical scrollbar as long as possible)
lines += lines > 1 ? 1 : 0;
QFontMetrics fm(pEditor->document()->defaultFont());
int newH = fm.lineSpacing() * lines;
// Limit editor to visible table height
int tableH = m_pTableView->viewport()->rect().height();
newH = std::min(newH, tableH);
// If the editor overflows the table view, move it up so it's not clipped.
// No need to care about y < 0 or y > (table height - line height) since the
// table already ensures visibility when the index is selected.
int newY = m_editRect.y();
if ((newY + newH) > tableH) {
newY = tableH - newH;
}
// Also limit width so scrollbars are visible and table is not scrolled if
// cursor is moved horizontally.
int newW = std::min(pEditor->width(), m_pTableView->viewport()->rect().width());
pEditor->setGeometry(QRect(m_editRect.x(), newY, newW, newH));
}
void MultiLineEditDelegate::commitAndCloseEditor() {
MultiLineEditor* pEditor = qobject_cast<MultiLineEditor*>(sender());
emit commitData(pEditor);
emit closeEditor(pEditor);
}
