Add FilterComboBox

This helper class is based on QComboBox, which has filtering of items
enabled by default.
It is intended to be used in places where QComboBoxes have a lot of
entries.
For example, the condition, action, or macro selection widgets.

CMakeLists.txt

@@ -257,6 +257,8 @@ target_sources(
           src/utils/log-helper.hpp
           src/utils/file-selection.cpp
           src/utils/file-selection.hpp
+          src/utils/filter-combo-box.cpp
+          src/utils/filter-combo-box.hpp
           src/utils/filter-selection.cpp
           src/utils/filter-selection.hpp
           src/utils/macro-list.cpp

src/utils/filter-combo-box.cpp

@@ -0,0 +1,87 @@
+#include "filter-combo-box.hpp"
+#include "utility.hpp"
+
+#include <QCompleter>
+#include <QLineEdit>
+#include <QFocusEvent>
+
+namespace advss {
+
+FilterComboBox::FilterComboBox(QWidget *parent, const QString &placehodler)
+	: QComboBox(parent)
+{
+	// Allow edit for completer but don't add new entries on pressing enter
+	setEditable(true);
+	setInsertPolicy(InsertPolicy::NoInsert);
+
+	if (!placehodler.isEmpty()) {
+		lineEdit()->setPlaceholderText(placehodler);
+	}
+
+	setMaxVisibleItems(30);
+
+	auto c = completer();
+	c->setCaseSensitivity(Qt::CaseInsensitive);
+	c->setFilterMode(Qt::MatchContains);
+	c->setCompletionMode(QCompleter::PopupCompletion);
+
+	connect(c, QOverload<const QModelIndex &>::of(&QCompleter::highlighted),
+		this, &FilterComboBox::CompleterHighlightChanged);
+	connect(lineEdit(), &QLineEdit::textChanged, this,
+		&FilterComboBox::TextChagned);
+}
+
+void FilterComboBox::focusOutEvent(QFocusEvent *event)
+{
+	// Reset on invalid selection
+	if (findText(currentText()) == -1) {
+		setCurrentIndex(-1);
+		emit currentIndexChanged(-1);
+		emit currentTextChanged("");
+	}
+
+	QComboBox::focusOutEvent(event);
+	_lastCompleterHighlightRow = -1;
+}
+
+static int findXthOccurance(QComboBox *list, int count, const QString &value)
+{
+	if (value.isEmpty() || count < 1) {
+		return -1;
+	}
+
+	const auto size = list->count();
+	int idx = FindIdxInRagne(list, 0, size, value.toStdString(),
+				 Qt::MatchContains | Qt::MatchFixedString);
+	if (count == 1) {
+		return idx;
+	}
+
+	for (int i = 1; i < count; i++) {
+		idx = FindIdxInRagne(list, idx, size, value.toStdString(),
+				     Qt::MatchContains | Qt::MatchFixedString);
+	}
+
+	return idx;
+}
+
+void FilterComboBox::CompleterHighlightChanged(const QModelIndex &index)
+{
+	_lastCompleterHighlightRow = index.row();
+	const auto text = currentText();
+	int idx = findXthOccurance(this, _lastCompleterHighlightRow, text);
+	emit currentIndexChanged(idx);
+	emit currentTextChanged(text);
+}
+
+void FilterComboBox::TextChagned(const QString &text)
+{
+	auto c = completer();
+	const bool completerActive = c->completionCount() > 0;
+	int count = completerActive ? _lastCompleterHighlightRow + 1 : 1;
+	int idx = findXthOccurance(this, count, text);
+	emit currentIndexChanged(idx);
+	emit currentTextChanged(text);
+}
+
+} // namespace advss

src/utils/filter-combo-box.hpp

@@ -0,0 +1,25 @@
+#pragma once
+#include <QComboBox>
+
+namespace advss {
+
+// Helper class which enables user to filter possible selections by typing
+class FilterComboBox : public QComboBox {
+	Q_OBJECT
+
+public:
+	FilterComboBox(QWidget *parent = nullptr,
+		       const QString &placehodler = "");
+
+protected:
+	void focusOutEvent(QFocusEvent *event) override;
+
+private slots:
+	void CompleterHighlightChanged(const QModelIndex &);
+	void TextChagned(const QString &);
+
+private:
+	int _lastCompleterHighlightRow = -1;
+};
+
+} // namespace advss