ClipboardHistory: Cap the history at 20 entries for now

Now that we can copy bitmaps, we need some kind of cap here or memory
usage quickly skyrockets.

This could probably be improved or made adaptive somehow, this is just
a simple hard cap for now.

MenuApplets/ClipboardHistory/ClipboardHistoryModel.cpp

@@ -71,6 +71,8 @@ void ClipboardHistoryModel::update()
 
 void ClipboardHistoryModel::add_item(const GUI::Clipboard::DataAndType& item)
 {
+ if (m_history_items.size() == m_history_limit)
+ m_history_items.take_last();
  m_history_items.prepend(item);
  update();
 }

MenuApplets/ClipboardHistory/ClipboardHistoryModel.h

@@ -53,4 +53,5 @@ class ClipboardHistoryModel final : public GUI::Model {
  virtual void update() override;
 
  Vector<GUI::Clipboard::DataAndType> m_history_items;
+ size_t m_history_limit { 20 };
 };