Implement Auto-Type {PICKCHARS}

* Closes #725

Support Auto-Type {PICKCHARS} placeholder. Open a dialog that lets you pick characters of an entry's password by their position. Supports typing {TAB} in between characters to move between fields (if necessary). Also supports using arrow keys to quickly navigate around the choice grid.

src/autotype/PickcharsDialog.h

@@ -0,0 +1,52 @@
+/*
+ *  Copyright (C) 2021 Team KeePassXC <team@keepassxc.org>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 2 or (at your option)
+ *  version 3 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef KEEPASSXC_PICKCHARSDIALOG_H
+#define KEEPASSXC_PICKCHARSDIALOG_H
+
+#include <QDialog>
+#include <QPointer>
+#include <QString>
+
+namespace Ui
+{
+    class PickcharsDialog;
+}
+
+class PickcharsDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    explicit PickcharsDialog(const QString& string, QWidget* parent = nullptr);
+    QString selectedChars();
+    bool pressTab();
+
+protected:
+    void showEvent(QShowEvent*) override;
+
+private slots:
+    void charSelected();
+    void upPressed();
+    void downPressed();
+
+private:
+    QSharedPointer<Ui::PickcharsDialog> m_ui;
+    int m_lastSelected;
+};
+
+#endif // KEEPASSXC_PICKCHARSDIALOG_H