Prepare for the ressurection of filtering

7 files changed, 191 insertions, 116 deletions

diff --git a/doc/bindings b/doc/bindings
index f586f0b3..db132cc7 100644
--- a/doc/bindings
+++ b/doc/bindings
@@ -381,6 +381,9 @@
 #def_key "ctrl-r"
 #  reverse_playlist
 #
+#def_key "ctrl-f"
+#  apply_filter
+#
 #def_key "ctrl-_"
 #  select_found_items
 #
diff --git a/src/actions.cpp b/src/actions.cpp
index b9045557..aa0a96d6 100644
--- a/src/actions.cpp
+++ b/src/actions.cpp
@@ -1934,6 +1934,14 @@ void ReversePlaylist::run()
 	Statusbar::print("Range reversed");
 }
 
+bool ApplyFilter::canBeRun()
+{
+	return false;
+}
+
+void ApplyFilter::run()
+{ }
+
 bool Find::canBeRun()
 {
 	return myScreen == myHelp
@@ -2724,6 +2732,7 @@ void populateActions()
 	insert_action(new Actions::ClearPlaylist());
 	insert_action(new Actions::SortPlaylist());
 	insert_action(new Actions::ReversePlaylist());
+	insert_action(new Actions::ApplyFilter());
 	insert_action(new Actions::Find());
 	insert_action(new Actions::FindItemForward());
 	insert_action(new Actions::FindItemBackward());
diff --git a/src/actions.h b/src/actions.h
index 1a6ee60b..34c504bf 100644
--- a/src/actions.h
+++ b/src/actions.h
@@ -122,6 +122,7 @@ enum class Type
 	ClearPlaylist,
 	SortPlaylist,
 	ReversePlaylist,
+	ApplyFilter,
 	Find,
 	FindItemForward,
 	FindItemBackward,
@@ -1036,6 +1037,15 @@ private:
 	NC::Menu<MPD::Song>::ConstIterator m_end;
 };
 
+struct ApplyFilter: public BaseAction
+{
+	ApplyFilter(): BaseAction(Type::ApplyFilter, "apply_filter") { }
+
+private:
+	virtual bool canBeRun() OVERRIDE;
+	virtual void run() OVERRIDE;
+};
+
 struct Find: BaseAction
 {
 	Find(): BaseAction(Type::Find, "find") { }
diff --git a/src/bindings.cpp b/src/bindings.cpp
index c2c0643f..1ce02f29 100644
--- a/src/bindings.cpp
+++ b/src/bindings.cpp
@@ -625,6 +625,8 @@ void BindingsConfiguration::generateDefaults()
 	}
 	if (notBound(k = stringToKey("ctrl-r")))
 		bind(k, Actions::Type::ReversePlaylist);
+	if (notBound(k = stringToKey("ctrl-f")))
+		bind(k, Actions::Type::ApplyFilter);
 	if (notBound(k = stringToKey("ctrl-_")))
 		bind(k, Actions::Type::SelectFoundItems);
 	if (notBound(k = stringToKey("/")))
diff --git a/src/help.cpp b/src/help.cpp
index 15fc1031..cb1305a9 100644
--- a/src/help.cpp
+++ b/src/help.cpp
@@ -210,6 +210,7 @@ void write_bindings(NC::Scrollpad &w)
 	key(w, Type::UpdateDatabase, "Start music database update");
 	w << '\n';
 	key(w, Type::ExecuteCommand, "Execute command");
+	key(w, Type::ApplyFilter, "Apply filter");
 	key(w, Type::FindItemForward, "Find item forward");
 	key(w, Type::FindItemBackward, "Find item backward");
 	key(w, Type::PreviousFoundItem, "Jump to previous found item");
diff --git a/src/menu.h b/src/menu.h
index d2783423..5711fd7e 100644
--- a/src/menu.h
+++ b/src/menu.h
@@ -96,6 +96,9 @@ struct List
 		bool isInactive() const { return m_properties & Inactive; }
 		bool isSeparator() const { return m_properties & Separator; }
 
+	protected:
+		unsigned properties() const { return m_properties; }
+
 	private:
 		unsigned m_properties;
 	};
@@ -174,17 +177,26 @@ template <typename ItemT> struct Menu : Window, List
 		
 		friend struct Menu<ItemT>;
 		
-		Item() { }
-		Item(ItemT value_, Properties::Type properties)
+		Item()
+			: m_value(std::make_shared<ItemT>(ItemT()))
+		{ }
+
+		template <typename ValueT>
+		Item(ValueT &&value_, Properties::Type properties)
 		: Properties(properties)
-		, m_value(value_)
+		, m_value(std::make_shared<ItemT>(std::forward<ValueT>(value_)))
 		{ }
 		
-		ItemT &value() { return m_value; }
-		const ItemT &value() const { return m_value; }
+		ItemT &value() { return *m_value; }
+		const ItemT &value() const { return *m_value; }
 		
-		ItemT &operator*() { return m_value; }
-		const ItemT &operator*() const { return m_value; }
+		ItemT &operator*() { return *m_value; }
+		const ItemT &operator*() const { return *m_value; }
+
+		// Make a deep copy of Item.
+		Item copy() const {
+			return Item(*m_value, static_cast<Properties::Type>(properties()));
+		}
 
 	private:
 		static Item mkSeparator()
@@ -195,9 +207,9 @@ template <typename ItemT> struct Menu : Window, List
 			return item;
 		}
 		
-		ItemT m_value;
+		std::shared_ptr<ItemT> m_value;
 	};
-	
+
 	typedef typename std::vector<Item>::iterator Iterator;
 	typedef typename std::vector<Item>::const_iterator ConstIterator;
 	typedef std::reverse_iterator<Iterator> ReverseIterator;
@@ -230,7 +242,7 @@ template <typename ItemT> struct Menu : Window, List
 	/// @see setItemDisplayer()
 	typedef std::function<void(Menu<ItemT> &)> ItemDisplayer;
 	
-	Menu() { }
+	Menu();
 	
 	Menu(size_t startx, size_t starty, size_t width, size_t height,
 			const std::string &title, Color color, Border border);
@@ -260,10 +272,6 @@ template <typename ItemT> struct Menu : Window, List
 	/// @param pos initial position of inserted separator
 	void insertSeparator(size_t pos);
 	
-	/// Deletes item from given position
-	/// @param pos given position of item to be deleted
-	void deleteItem(size_t pos);
-	
 	/// Moves the highlighted position to the given line of window
 	/// @param y Y position of menu window to be highlighted
 	/// @return true if the position is reachable, false otherwise
@@ -271,10 +279,10 @@ template <typename ItemT> struct Menu : Window, List
 	
 	/// Checks if list is empty
 	/// @return true if list is empty, false otherwise
-	virtual bool empty() const OVERRIDE { return m_items.empty(); }
+	virtual bool empty() const OVERRIDE { return m_items->empty(); }
 
 	/// @return size of the list
-	virtual size_t size() const OVERRIDE { return m_items.size(); }
+	virtual size_t size() const OVERRIDE { return m_items->size(); }
 
 	/// @return currently highlighted position
 	virtual size_t choice() const OVERRIDE;
@@ -298,7 +306,24 @@ template <typename ItemT> struct Menu : Window, List
 	
 	/// Sets highlighted position to 0
 	void reset();
-	
+
+	/// Apply filter predicate to items in the menu and show the ones for which it
+	/// returned true.
+	template <typename FilterPredicate>
+	bool applyFilter(FilterPredicate &&p);
+
+	/// Clear results of applyFilter and show all items.
+	void clearFilter();
+
+	/// @return true if menu is filtered.
+	bool isFiltered() const { return m_items == &m_filtered_items; }
+
+	/// Show all items.
+	void showAllItems() { m_items = &m_all_items; }
+
+	/// Show filtered items.
+	void showFilteredItems() { m_items = &m_filtered_items; }
+
 	/// Sets prefix, that is put before each selected item to indicate its selection
 	/// Note that the passed variable is not deleted along with menu object.
 	/// @param b pointer to buffer that contains the prefix
@@ -336,23 +361,23 @@ template <typename ItemT> struct Menu : Window, List
 	/// @param pos requested position
 	/// @return reference to item at given position
 	/// @throw std::out_of_range if given position is out of range
-	Menu<ItemT>::Item &at(size_t pos) { return m_items.at(pos); }
+	Menu<ItemT>::Item &at(size_t pos) { return m_items->at(pos); }
 	
 	/// @param pos requested position
 	/// @return const reference to item at given position
 	/// @throw std::out_of_range if given position is out of range
-	const Menu<ItemT>::Item &at(size_t pos) const { return m_items.at(pos); }
+	const Menu<ItemT>::Item &at(size_t pos) const { return m_items->at(pos); }
 	
 	/// @param pos requested position
 	/// @return const reference to item at given position
-	const Menu<ItemT>::Item &operator[](size_t pos) const { return m_items[pos]; }
+	const Menu<ItemT>::Item &operator[](size_t pos) const { return (*m_items)[pos]; }
 	
 	/// @param pos requested position
 	/// @return const reference to item at given position
-	Menu<ItemT>::Item &operator[](size_t pos) { return m_items[pos]; }
+	Menu<ItemT>::Item &operator[](size_t pos) { return (*m_items)[pos]; }
 	
-	Iterator current() { return Iterator(m_items.begin() + m_highlight); }
-	ConstIterator current() const { return ConstIterator(m_items.begin() + m_highlight); }
+	Iterator current() { return Iterator(m_items->begin() + m_highlight); }
+	ConstIterator current() const { return ConstIterator(m_items->begin() + m_highlight); }
 	ReverseIterator rcurrent() {
 		if (empty())
 			return rend();
@@ -366,8 +391,8 @@ template <typename ItemT> struct Menu : Window, List
 			return ConstReverseIterator(++current());
 	}
 
-	ValueIterator currentV() { return ValueIterator(m_items.begin() + m_highlight); }
-	ConstValueIterator currentV() const { return ConstValueIterator(m_items.begin() + m_highlight); }
+	ValueIterator currentV() { return ValueIterator(m_items->begin() + m_highlight); }
+	ConstValueIterator currentV() const { return ConstValueIterator(m_items->begin() + m_highlight); }
 	ReverseValueIterator rcurrentV() {
 		if (empty())
 			return rendV();
@@ -381,10 +406,10 @@ template <typename ItemT> struct Menu : Window, List
 			return ConstReverseValueIterator(++currentV());
 	}
 	
-	Iterator begin() { return Iterator(m_items.begin()); }
-	ConstIterator begin() const { return ConstIterator(m_items.begin()); }
-	Iterator end() { return Iterator(m_items.end()); }
-	ConstIterator end() const { return ConstIterator(m_items.end()); }
+	Iterator begin() { return Iterator(m_items->begin()); }
+	ConstIterator begin() const { return ConstIterator(m_items->begin()); }
+	Iterator end() { return Iterator(m_items->end()); }
+	ConstIterator end() const { return ConstIterator(m_items->end()); }
 	
 	ReverseIterator rbegin() { return ReverseIterator(end()); }
 	ConstReverseIterator rbegin() const { return ConstReverseIterator(end()); }
@@ -402,34 +427,36 @@ template <typename ItemT> struct Menu : Window, List
 	ConstReverseValueIterator rendV() const { return ConstReverseValueIterator(beginV()); }
 	
 	virtual List::Iterator currentP() OVERRIDE {
-		return List::Iterator(PropertiesIterator(m_items.begin() + m_highlight));
+		return List::Iterator(PropertiesIterator(m_items->begin() + m_highlight));
 	}
 	virtual List::ConstIterator currentP() const OVERRIDE {
-		return List::ConstIterator(ConstPropertiesIterator(m_items.begin() + m_highlight));
+		return List::ConstIterator(ConstPropertiesIterator(m_items->begin() + m_highlight));
 	}
 	virtual List::Iterator beginP() OVERRIDE {
-		return List::Iterator(PropertiesIterator(m_items.begin()));
+		return List::Iterator(PropertiesIterator(m_items->begin()));
 	}
 	virtual List::ConstIterator beginP() const OVERRIDE {
-		return List::ConstIterator(ConstPropertiesIterator(m_items.begin()));
+		return List::ConstIterator(ConstPropertiesIterator(m_items->begin()));
 	}
 	virtual List::Iterator endP() OVERRIDE {
-		return List::Iterator(PropertiesIterator(m_items.end()));
+		return List::Iterator(PropertiesIterator(m_items->end()));
 	}
 	virtual List::ConstIterator endP() const OVERRIDE {
-		return List::ConstIterator(ConstPropertiesIterator(m_items.end()));
+		return List::ConstIterator(ConstPropertiesIterator(m_items->end()));
 	}
 
 private:
 	bool isHighlightable(size_t pos)
 	{
-		return !m_items[pos].isSeparator()
-		    && !m_items[pos].isInactive();
+		return !(*m_items)[pos].isSeparator()
+			&& !(*m_items)[pos].isInactive();
 	}
 	
 	ItemDisplayer m_item_displayer;
 	
-	std::vector<Item> m_items;
+	std::vector<Item> *m_items;
+	std::vector<Item> m_all_items;
+	std::vector<Item> m_filtered_items;
 	
 	size_t m_beginning;
 	size_t m_highlight;
diff --git a/src/menu_impl.h b/src/menu_impl.h
index f3eefa6d..33b8a24f 100644
--- a/src/menu_impl.h
+++ b/src/menu_impl.h
@@ -26,59 +26,72 @@
 namespace NC {
 
 template <typename ItemT>
+Menu<ItemT>::Menu()
+{
+	m_items = &m_all_items;
+}
+
+template <typename ItemT>
 Menu<ItemT>::Menu(size_t startx,
-	size_t starty,
-	size_t width,
-	size_t height,
-	const std::string &title,
-	Color color,
-	Border border)
-	: Window(startx, starty, width, height, title, std::move(color), border),
-	m_item_displayer(0),
-	m_beginning(0),
-	m_highlight(0),
-	m_highlight_color(m_base_color),
-	m_highlight_enabled(true),
-	m_cyclic_scroll_enabled(false),
-	m_autocenter_cursor(false)
+                  size_t starty,
+                  size_t width,
+                  size_t height,
+                  const std::string &title,
+                  Color color,
+                  Border border)
+	: Window(startx, starty, width, height, title, std::move(color), border)
+	, m_item_displayer(0)
+	, m_beginning(0)
+	, m_highlight(0)
+	, m_highlight_color(m_base_color)
+	, m_highlight_enabled(true)
+	, m_cyclic_scroll_enabled(false)
+	, m_autocenter_cursor(false)
 {
+	m_items = &m_all_items;
 }
 
 template <typename ItemT>
 Menu<ItemT>::Menu(const Menu &rhs)
-: Window(rhs)
-, m_item_displayer(rhs.m_item_displayer)
-, m_beginning(rhs.m_beginning)
-, m_highlight(rhs.m_highlight)
-, m_highlight_color(rhs.m_highlight_color)
-, m_highlight_enabled(rhs.m_highlight_enabled)
-, m_cyclic_scroll_enabled(rhs.m_cyclic_scroll_enabled)
-, m_autocenter_cursor(rhs.m_autocenter_cursor)
-, m_drawn_position(rhs.m_drawn_position)
-, m_selected_prefix(rhs.m_selected_prefix)
-, m_selected_suffix(rhs.m_selected_suffix)
+	: Window(rhs)
+	, m_item_displayer(rhs.m_item_displayer)
+	, m_beginning(rhs.m_beginning)
+	, m_highlight(rhs.m_highlight)
+	, m_highlight_color(rhs.m_highlight_color)
+	, m_highlight_enabled(rhs.m_highlight_enabled)
+	, m_cyclic_scroll_enabled(rhs.m_cyclic_scroll_enabled)
+	, m_autocenter_cursor(rhs.m_autocenter_cursor)
+	, m_drawn_position(rhs.m_drawn_position)
+	, m_selected_prefix(rhs.m_selected_prefix)
+	, m_selected_suffix(rhs.m_selected_suffix)
 {
-	// there is no way to properly fill m_filtered_options
-	// (if rhs is filtered), so we just don't do it.
-	m_items.reserve(rhs.m_items.size());
-	std::copy(rhs.begin(), rhs.end(), std::back_inserter(m_items));
+	// TODO: move filtered items
+	m_all_items.reserve(rhs.m_all_items.size());
+	for (const auto &item : rhs.m_all_items)
+		m_all_items.push_back(item.copy());
+	m_items = &m_all_items;
 }
 
 template <typename ItemT>
 Menu<ItemT>::Menu(Menu &&rhs)
-: Window(rhs)
-, m_item_displayer(rhs.m_item_displayer)
-, m_items(std::move(rhs.m_items))
-, m_beginning(rhs.m_beginning)
-, m_highlight(rhs.m_highlight)
-, m_highlight_color(rhs.m_highlight_color)
-, m_highlight_enabled(rhs.m_highlight_enabled)
-, m_cyclic_scroll_enabled(rhs.m_cyclic_scroll_enabled)
-, m_autocenter_cursor(rhs.m_autocenter_cursor)
-, m_drawn_position(rhs.m_drawn_position)
-, m_selected_prefix(std::move(rhs.m_selected_prefix))
-, m_selected_suffix(std::move(rhs.m_selected_suffix))
+	: Window(rhs)
+	, m_item_displayer(rhs.m_item_displayer)
+	, m_all_items(std::move(rhs.m_all_items))
+	, m_filtered_items(std::move(rhs.m_filtered_items))
+	, m_beginning(rhs.m_beginning)
+	, m_highlight(rhs.m_highlight)
+	, m_highlight_color(rhs.m_highlight_color)
+	, m_highlight_enabled(rhs.m_highlight_enabled)
+	, m_cyclic_scroll_enabled(rhs.m_cyclic_scroll_enabled)
+	, m_autocenter_cursor(rhs.m_autocenter_cursor)
+	, m_drawn_position(rhs.m_drawn_position)
+	, m_selected_prefix(std::move(rhs.m_selected_prefix))
+	, m_selected_suffix(std::move(rhs.m_selected_suffix))
 {
+	if (rhs.m_items == &rhs.m_all_items)
+		m_items = &m_all_items;
+	else
+		m_items = &m_filtered_items;
 }
 
 template <typename ItemT>
@@ -86,7 +99,8 @@ Menu<ItemT> &Menu<ItemT>::operator=(Menu rhs)
 {
 	std::swap(static_cast<Window &>(*this), static_cast<Window &>(rhs));
 	std::swap(m_item_displayer, rhs.m_item_displayer);
-	std::swap(m_items, rhs.m_items);
+	std::swap(m_all_items, rhs.m_all_items);
+	std::swap(m_filtered_items, rhs.m_filtered_items);
 	std::swap(m_beginning, rhs.m_beginning);
 	std::swap(m_highlight, rhs.m_highlight);
 	std::swap(m_highlight_color, rhs.m_highlight_color);
@@ -96,52 +110,41 @@ Menu<ItemT> &Menu<ItemT>::operator=(Menu rhs)
 	std::swap(m_drawn_position, rhs.m_drawn_position);
 	std::swap(m_selected_prefix, rhs.m_selected_prefix);
 	std::swap(m_selected_suffix, rhs.m_selected_suffix);
+	if (rhs.m_items == &rhs.m_all_items)
+		m_items = &m_all_items;
+	else
+		m_items = &m_filtered_items;
 	return *this;
 }
 
 template <typename ItemT>
 void Menu<ItemT>::resizeList(size_t new_size)
 {
-	if (new_size > m_items.size())
-	{
-		size_t old_size = m_items.size();
-		m_items.resize(new_size);
-		for (size_t i = old_size; i < new_size; ++i)
-			m_items[i] = Item();
-	}
-	else
-		m_items.resize(new_size);
+	m_all_items.resize(new_size);
 }
 
 template <typename ItemT>
 void Menu<ItemT>::addItem(ItemT item, Properties::Type properties)
 {
-	m_items.push_back(Item(std::move(item), properties));
+	m_all_items.push_back(Item(std::move(item), properties));
 }
 
 template <typename ItemT>
 void Menu<ItemT>::addSeparator()
 {
-	m_items.push_back(Item::mkSeparator());
+	m_all_items.push_back(Item::mkSeparator());
 }
 
 template <typename ItemT>
 void Menu<ItemT>::insertItem(size_t pos, ItemT item, Properties::Type properties)
 {
-	m_items.insert(m_items.begin()+pos, Item(std::move(item), properties));
+	m_all_items.insert(m_all_items.begin()+pos, Item(std::move(item), properties));
 }
 
 template <typename ItemT>
 void Menu<ItemT>::insertSeparator(size_t pos)
 {
-	m_items.insert(m_items.begin()+pos, Item::mkSeparator());
-}
-
-template <typename ItemT>
-void Menu<ItemT>::deleteItem(size_t pos)
-{
-	assert(pos < m_items.size());
-	m_items.erase(m_items.begin()+pos);
+	m_all_items.insert(m_all_items.begin()+pos, Item::mkSeparator());
 }
 
 template <typename ItemT>
@@ -156,7 +159,7 @@ bool Menu<ItemT>::Goto(size_t y)
 template <typename ItemT>
 void Menu<ItemT>::refresh()
 {
-	if (m_items.empty())
+	if (m_items->empty())
 	{
 		Window::clear();
 		Window::refresh();
@@ -164,14 +167,14 @@ void Menu<ItemT>::refresh()
 	}
 
 	size_t max_beginning = 0;
-	if (m_items.size() > m_height)
-		max_beginning = m_items.size() - m_height;
+	if (m_items->size() > m_height)
+		max_beginning = m_items->size() - m_height;
 	m_beginning = std::min(m_beginning, max_beginning);
 
 	// if highlighted position is off the screen, make it visible
 	m_highlight = std::min(m_highlight, m_beginning+m_height-1);
 	// if highlighted position is invalid, correct it
-	m_highlight = std::min(m_highlight, m_items.size()-1);
+	m_highlight = std::min(m_highlight, m_items->size()-1);
 
 	if (!isHighlightable(m_highlight))
 	{
@@ -186,18 +189,18 @@ void Menu<ItemT>::refresh()
 	for (; m_drawn_position < end_; ++m_drawn_position, ++line)
 	{
 		goToXY(0, line);
-		if (m_drawn_position >= m_items.size())
+		if (m_drawn_position >= m_items->size())
 		{
 			for (; line < m_height; ++line)
 				mvwhline(m_window, line, 0, NC::Key::Space, m_width);
 			break;
 		}
-		if (m_items[m_drawn_position].isSeparator())
+		if ((*m_items)[m_drawn_position].isSeparator())
 		{
 			mvwhline(m_window, line, 0, 0, m_width);
 			continue;
 		}
-		if (m_items[m_drawn_position].isBold())
+		if ((*m_items)[m_drawn_position].isBold())
 			*this << Format::Bold;
 		if (m_highlight_enabled && m_drawn_position == m_highlight)
 		{
@@ -205,18 +208,18 @@ void Menu<ItemT>::refresh()
 			*this << m_highlight_color;
 		}
 		mvwhline(m_window, line, 0, NC::Key::Space, m_width);
-		if (m_items[m_drawn_position].isSelected())
+		if ((*m_items)[m_drawn_position].isSelected())
 			*this << m_selected_prefix;
 		if (m_item_displayer)
 			m_item_displayer(*this);
-		if (m_items[m_drawn_position].isSelected())
+		if ((*m_items)[m_drawn_position].isSelected())
 			*this << m_selected_suffix;
 		if (m_highlight_enabled && m_drawn_position == m_highlight)
 		{
 			*this << Color::End;
 			*this << Format::NoReverse;
 		}
-		if (m_items[m_drawn_position].isBold())
+		if ((*m_items)[m_drawn_position].isBold())
 			*this << Format::NoBold;
 	}
 	Window::refresh();
@@ -225,10 +228,10 @@ void Menu<ItemT>::refresh()
 template <typename ItemT>
 void Menu<ItemT>::scroll(Scroll where)
 {
-	if (m_items.empty())
+	if (m_items->empty())
 		return;
-	size_t max_highlight = m_items.size()-1;
-	size_t max_beginning = m_items.size() < m_height ? 0 : m_items.size()-m_height;
+	size_t max_highlight = m_items->size()-1;
+	size_t max_beginning = m_items->size() < m_height ? 0 : m_items->size()-m_height;
 	size_t max_visible_highlight = m_beginning+m_height-1;
 	switch (where)
 	{
@@ -323,13 +326,15 @@ void Menu<ItemT>::reset()
 template <typename ItemT>
 void Menu<ItemT>::clear()
 {
-	m_items.clear();
+	m_all_items.clear();
+	m_filtered_items.clear();
+	m_items = &m_all_items;
 }
 
 template <typename ItemT>
 void Menu<ItemT>::highlight(size_t pos)
 {
-	assert(pos < m_items.size());
+	assert(pos < m_items->size());
 	m_highlight = pos;
 	size_t half_height = m_height/2;
 	if (pos < half_height)
@@ -345,6 +350,24 @@ size_t Menu<ItemT>::choice() const
 	return m_highlight;
 }
 
+template <typename ItemT> template <typename FilterPredicate>
+bool Menu<ItemT>::applyFilter(FilterPredicate &&p)
+{
+	m_filtered_items.clear();
+	for (const auto &item : m_all_items)
+		if (p(item))
+			m_filtered_items.push_back(item);
+	m_items = &m_filtered_items;
+	return !m_filtered_items.empty();
+}
+
+template <typename ItemT>
+void Menu<ItemT>::clearFilter()
+{
+	m_filtered_items.clear();
+	m_items = &m_all_items;
+}
+
 }
 
-#endif // NCMPCPP_MENU_IMPL_H
\ No newline at end of file
+#endif // NCMPCPP_MENU_IMPL_H