QTreeView: column resize from columns and not from headers? - qt

Question

Is there any way to allow the user to interactively resize the columns when headers are hidden?

Answer 1

You can install an event filter on the table's viewport and implement needed behavior manually. Below is a sample implementation.
Header:
#include <QTableView>
class Table_cell_resizer : public QObject {
Q_OBJECT
public:
explicit Table_cell_resizer(QTableView *view = 0);
protected:
bool eventFilter(QObject* object, QEvent* event);
private:
QTableView* m_view;
//max distance between mouse and a cell, small enough to trigger resize
int m_sensibility;
//variables for saving state while dragging
bool m_drag_in_progress;
Qt::Orientation m_drag_orientation;
int m_drag_section;
int m_drag_previous_pos;
// check if mouse_pos is around right or bottom side of a cell
// (depending on orientation)
// and return the index of that cell if found
QModelIndex index_resizable(QPoint mouse_pos, Qt::Orientation orientation);
};
Source:
#include "Table_cell_resizer.h"
#include <QMouseEvent>
#include <QHeaderView>
Table_cell_resizer::Table_cell_resizer(QTableView* view) :
QObject(view), m_view(view)
{
m_view->viewport()->installEventFilter(this);
m_view->viewport()->setMouseTracking(true);
m_sensibility = 5;
m_drag_in_progress = false;
}
bool Table_cell_resizer::eventFilter(QObject* object, QEvent* event) {
if (object == m_view->viewport()) {
QMouseEvent* mouse_event = dynamic_cast<QMouseEvent*>(event);
if (mouse_event) {
if (mouse_event->type() == QEvent::MouseMove) {
if (m_drag_in_progress) { // apply dragging
int delta;
QHeaderView* header_view;
if (m_drag_orientation == Qt::Vertical) {
delta = mouse_event->pos().y() - m_drag_previous_pos;
header_view = m_view->verticalHeader();
m_drag_previous_pos = mouse_event->pos().y();
} else if (m_drag_orientation == Qt::Horizontal) {
delta = mouse_event->pos().x() - m_drag_previous_pos;
header_view = m_view->horizontalHeader();
m_drag_previous_pos = mouse_event->pos().x();
}
//using minimal size = m_sensibility * 2 to prevent collapsing
header_view->resizeSection(m_drag_section,
qMax(m_sensibility * 2, header_view->sectionSize(m_drag_section) + delta));
return true;
} else { // set mouse cursor shape
if (index_resizable(mouse_event->pos(), Qt::Vertical).isValid()) {
m_view->viewport()->setCursor(Qt::SplitVCursor);
} else if (index_resizable(mouse_event->pos(), Qt::Horizontal).isValid()) {
m_view->viewport()->setCursor(Qt::SplitHCursor);
} else {
m_view->viewport()->setCursor(QCursor());
}
}
} else if (mouse_event->type() == QEvent::MouseButtonPress &&
mouse_event->button() == Qt::LeftButton &&
!m_drag_in_progress) { // start dragging
if (index_resizable(mouse_event->pos(), Qt::Vertical).isValid()) {
m_drag_in_progress = true;
m_drag_orientation = Qt::Vertical;
m_drag_previous_pos = mouse_event->y();
m_drag_section = index_resizable(mouse_event->pos(), Qt::Vertical).row();
return true;
} else if (index_resizable(mouse_event->pos(), Qt::Horizontal).isValid()) {
m_drag_in_progress = true;
m_drag_orientation = Qt::Horizontal;
m_drag_previous_pos = mouse_event->x();
m_drag_section = index_resizable(mouse_event->pos(), Qt::Horizontal).column();
return true;
}
} else if (mouse_event->type() == QEvent::MouseButtonRelease &&
mouse_event->button() == Qt::LeftButton &&
m_drag_in_progress) { // stop dragging
m_drag_in_progress = false;
return true;
}
}
}
return false;
}
QModelIndex Table_cell_resizer::index_resizable(QPoint mouse_pos, Qt::Orientation orientation) {
QModelIndex index = m_view->indexAt(mouse_pos - QPoint(m_sensibility + 1, m_sensibility + 1));
if (index.isValid()) {
if (orientation == Qt::Horizontal) {
if (qAbs(m_view->visualRect(index).right() - mouse_pos.x()) < m_sensibility &&
m_view->horizontalHeader()->sectionResizeMode(index.column()) == QHeaderView::Interactive) {
return index;
}
} else {
if (qAbs(m_view->visualRect(index).bottom() - mouse_pos.y()) < m_sensibility &&
m_view->verticalHeader()->sectionResizeMode(index.row()) == QHeaderView::Interactive) {
return index;
}
}
}
return QModelIndex();
}
Usage:
new Table_cell_resizer(ui->table);
User can now resize rows and columns using cell area in addition to header areas. You can hide headers if you wish. This implementation respects header resize modes, so make sure that resize mode is set to QHeaderView::Interactive for headers which you want to be resizable. For example, you can set horizontal header mode to Interactive and vertical header mode to Fixed, resulting in resizable columns and fixed rows.