filter: add a filter constraint widget

This add a widget that represents a single filter constraint. Since
filter constraints are very general, the widget has to consider a
number of cases:
- numerical ranges
- star-widget ranges
- string lists
- multiple choice lists
Moreover, it supports units, which must be updated when the preferences
change.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

desktop-widgets/filterconstraintwidget.h

@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef FILTERCONSTRAINTWIDGET_H
+#define FILTERCONSTRAINTWIDGET_H
+
+#include "core/filterconstraint.h"
+#include <QWidget>
+#include <memory>
+
+class FilterConstraintModel;
+class QComboBox;
+class QDateEdit;
+class QDoubleSpinBox;
+class QGridLayout;
+class QHBoxLayout;
+class QLabel;
+class QLineEdit;
+class QListWidget;
+class QPushButton;
+class QTimeEdit;
+class StarWidget;
+
+// Technically, this is not a single widget, but numerous widgets,
+// which are added to the row of a QGridLayout
+class FilterConstraintWidget : public QObject {
+	Q_OBJECT
+public:
+	FilterConstraintWidget(FilterConstraintModel *model, const QModelIndex &index, QGridLayout *layout);
+	~FilterConstraintWidget();
+	void moveToRow(int row); // call if the row of the widget has changed.
+				 // this will update the index used to access the model as well as the position in the layout
+	void update();
+private
+slots:
+	void trash();
+	void stringEdited(const QString &s);
+	void multipleChoiceEdited();
+	void negateEdited(int index);
+	void rangeModeEdited(int index);
+	void stringModeEdited(int index);
+	void fromEditedInt(int i);
+	void toEditedInt(int i);
+	void fromEditedFloat(double f);
+	void toEditedFloat(double f);
+	void fromEditedTimestamp(const QDateTime &datetime);
+	void toEditedTimestamp(const QDateTime &datetime);
+private:
+	QGridLayout *layout;
+	FilterConstraintModel *model;
+	int row;
+	const filter_constraint_type type; // we don't support changing the type
+	void addToLayout();
+	void removeFromLayout();
+
+	std::unique_ptr<QHBoxLayout> rangeLayout;
+	std::unique_ptr<QPushButton> trashButton;
+	std::unique_ptr<QLabel> typeLabel;
+	std::unique_ptr<QComboBox> negate;
+	std::unique_ptr<QComboBox> stringMode;
+	std::unique_ptr<QComboBox> rangeMode;
+	std::unique_ptr<QListWidget> multipleChoice;
+	std::unique_ptr<QLineEdit> string;
+	std::unique_ptr<StarWidget> starFrom, starTo;
+	std::unique_ptr<QDoubleSpinBox> spinBoxFrom, spinBoxTo;
+	std::unique_ptr<QDateEdit> dateFrom, dateTo;
+	std::unique_ptr<QTimeEdit> timeFrom, timeTo;
+	std::unique_ptr<QLabel> unitFrom, unitTo;
+	std::unique_ptr<QLabel> toLabel;
+};
+
+#endif