deselectabletreeview.h

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// SPDX-FileCopyrightText: 2016 Anne Jan Brouwer
// SPDX-License-Identifier: GPL-3.0-or-later
#ifndef SRC_DESELECTABLETREEVIEW_H_
#define SRC_DESELECTABLETREEVIEW_H_
 
#include <QGuiApplication>
#include <QMouseEvent>
#include <QStyleHints>
#include <QTimer>
#include <QTreeView>

class DeselectableTreeView : public QTreeView {
  Q_OBJECT
 
public:
  explicit DeselectableTreeView(QWidget *parent) : QTreeView(parent) {
    deselectTimer.setSingleShot(true);
    connect(&deselectTimer, &QTimer::timeout, this,
            &DeselectableTreeView::deselect);
  }

  ~DeselectableTreeView() override = default;
 
signals:
  void emptyClicked();
 
private:
  bool doubleClickHappened = false;
  bool clickSelected = false;
  QTimer deselectTimer;

  void mousePressEvent(QMouseEvent *event) override {
    // A new press belongs to a new click: whatever the previous release left
    // pending must not clear the selection this press is about to make.
    deselectTimer.stop();
    clickSelected =
        selectionModel()->isSelected(indexAt(event->position().toPoint()));
    QTreeView::mousePressEvent(event);
  }

  void mouseReleaseEvent(QMouseEvent *event) override {
    const QModelIndex item = indexAt(event->position().toPoint());
    const bool pressWasOnSelection = clickSelected;
    clickSelected = false;
 
    // Handle the release immediately: waiting here would delay selection —
    // and therefore every decrypt — by the double-click interval.
    QTreeView::mouseReleaseEvent(event);
 
    const bool emptyOrSelected =
        !item.isValid() || selectionModel()->isSelected(item);
    if (!pressWasOnSelection || !emptyOrSelected)
      return;
 
    // Deselecting is the one decision that must wait: a double-click starts
    // with a release, and opening the editor must win over clearing the
    // selection. Ask the platform how long a double-click may take instead
    // of assuming 200 ms.
    doubleClickHappened = false;
    deselectTimer.start(
        QGuiApplication::styleHints()->mouseDoubleClickInterval());
  }

  void deselect() {
    if (doubleClickHappened)
      return;
    clearSelection();
    selectionModel()->setCurrentIndex(QModelIndex(),
                                      QItemSelectionModel::Select);
    emit emptyClicked();
  }

  void mouseDoubleClickEvent(QMouseEvent *event) override {
    doubleClickHappened = true;
    deselectTimer.stop();
    QTreeView::mouseDoubleClickEvent(event);
  }
};
 
#endif // SRC_DESELECTABLETREEVIEW_H_