Store pattern in completion view, not model.

The pattern property is used for highlighting. It is purely
display-related, so it should be in the view rather than the model.

qutebrowser/completion/completiondelegate.py

@@ -196,7 +196,8 @@ class CompletionItemDelegate(QStyledItemDelegate):
         self._doc.setDocumentMargin(2)
 
         if index.parent().isValid():
-            pattern = index.model().pattern
+            view = self.parent()
+            pattern = view.pattern
             columns_to_filter = index.model().columns_to_filter(index)
             if index.column() in columns_to_filter and pattern:
                 repl = r'<span class="highlight">\g<0></span>'

qutebrowser/completion/completionwidget.py

@@ -40,6 +40,7 @@ class CompletionView(QTreeView):
     headers, and children show as flat list.
 
     Attributes:
+        pattern: Current filter pattern, used for highlighting.
         _win_id: The ID of the window this CompletionView is associated with.
         _height: The height to use for the CompletionView.
         _height_perc: Either None or a percentage if height should be relative.
@@ -106,6 +107,7 @@ class CompletionView(QTreeView):
 
     def __init__(self, win_id, parent=None):
         super().__init__(parent)
+        self.pattern = ''
         self._win_id = win_id
         # FIXME handle new aliases.
         # objreg.get('config').changed.connect(self.init_command_completion)
@@ -288,6 +290,7 @@ class CompletionView(QTreeView):
             self.expand(model.index(i, 0))
 
     def set_pattern(self, pattern):
+        self.pattern = pattern
         with debug.log_time(log.completion, 'Set pattern {}'.format(pattern)):
             self.model().set_pattern(pattern)
             self._resize_columns()

qutebrowser/completion/models/completionmodel.py

@@ -35,7 +35,6 @@ class CompletionModel(QAbstractItemModel):
     Attributes:
         column_widths: The width percentages of the columns used in the
                        completion view.
-        pattern: Current filter pattern, used for highlighting.
         _categories: The sub-categories.
     """
 
@@ -43,7 +42,6 @@ class CompletionModel(QAbstractItemModel):
         super().__init__(parent)
         self.column_widths = column_widths
         self._categories = []
-        self.pattern = ''
 
     def _cat_from_idx(self, index):
         """Return the category pointed to by the given index.
@@ -180,8 +178,6 @@ class CompletionModel(QAbstractItemModel):
             pattern: The filter pattern to set.
         """
         log.completion.debug("Setting completion pattern '{}'".format(pattern))
-        # TODO: should pattern be saved in the view layer instead?
-        self.pattern = pattern
         for cat in self._categories:
             cat.set_pattern(pattern)