added eviction, attached it to list changes signal

grum/dictlist/dictlistwidget.py

@@ -14,8 +14,12 @@ class DictListWidget(QListWidget):
         self.setSelectionMode(QListWidget.ExtendedSelection)
         self.items = {}
         self._add_menu()
+
         shortcut(self, "Del", self.delete_selected, context=Qt.WidgetShortcut)
 
+        self.nkeep = None
+        self.model().rowsInserted.connect(self.on_evict)
+
 
     def _add_menu(self):
         self.menu = menu = RClickMenu(self)
@@ -100,6 +104,7 @@ class DictListWidget(QListWidget):
 
 
     def enable_sort_by_timestamp(self):
+        # fall back to name for identical timestamps
         self.set_sort_key(lambda x: (x.timestamps.max(), x.text()))
 
 
@@ -107,4 +112,33 @@ class DictListWidget(QListWidget):
         self.set_sort_key(None)
 
 
+    def set_nkeep(self, n):
+        self.nkeep = n
+        self.on_evict()
+
+
+    def on_evict(self):
+        if self.nkeep:
+            self.evict(self.nkeep)
+
+
+    def evict(self, nkeep):
+        items = self.items.values()
+
+        # map order in dict to indices
+        mapping = enumerate(items)
+        mapping = {item.text(): index for index, item in mapping}
+
+        def sk(x):
+            # fall back to insertion order for identical timestamps
+            return (x.timestamps.max(), mapping[x.text()])
+
+        items = sorted(items, key=sk, reverse=True)
+        items_to_evict = items[nkeep:]
+
+        for i in items_to_evict:
+            self.items.pop(i.key)
+            self.deleteItem(i)
+
+