cmds: clear diffs when the selection becomes empty

Detect the empty state and refresh the diff text and selection.
We originally used a separate event to track clicks, which made
the code harder to follow.

We now check for the empty state in when refreshing and empty
out the diff text when no selection or no changes exist.

Closes #194

Reported-by: Avinash-Bhat <nashpapa@gmail.com>
Signed-off-by: David Aguilar <davvid@gmail.com>

cola/main/model.py

@@ -13,6 +13,7 @@
 from cola.compat import set
 from cola.observable import Observable
 from cola.decorators import memoize
+from cola.models.selection import selection_model
 
 
 # Static GitConfig instance
@@ -190,6 +191,12 @@ def _update_files(self, update_index=False):
         self.untracked = state.get('untracked', [])
         self.submodules = state.get('submodules', set())
         self.upstream_changed = state.get('upstream_changed', [])
+        if self.is_empty() or selection_model().is_empty():
+            self.set_diff_text('')
+
+    def is_empty(self):
+        return not(bool(self.staged or self.modified or
+                        self.unmerged or self.untracked))
 
     def _update_refs(self):
         self.remotes = self.git.remote().splitlines()

cola/models/selection.py

@@ -50,6 +50,10 @@ def __init__(self):
         self.modified = []
         self.untracked = []
 
+    def is_empty(self):
+        return not(bool(self.staged or self.unmerged or
+                        self.modified or self.untracked))
+
     def set_selection(self, s):
         """Set the new selection."""
         self.staged = s.staged

cola/widgets/diff.py

@@ -60,11 +60,16 @@ def __init__(self, parent):
 
         model.add_observer(model.message_mode_about_to_change,
                            self._mode_about_to_change)
-        model.add_observer(model.message_diff_text_changed, self.setPlainText)
+        model.add_observer(model.message_diff_text_changed, self._emit_text)
 
         self.connect(self, SIGNAL('copyAvailable(bool)'),
                      self.enable_selection_actions)
 
+        self.connect(self, SIGNAL('set_text'), self.setPlainText)
+
+    def _emit_text(self, text):
+        self.emit(SIGNAL('set_text'), text)
+
     # Qt overrides
     def contextMenuEvent(self, event):
         """Create the context menu for the diff display."""

cola/widgets/status.py

@@ -79,6 +79,7 @@ def __init__(self, parent):
         self.old_selection = None
         self.old_contents = None
         self.old_current_item = None
+        self.busy = False
 
         self.expanded_items = set()
 
@@ -134,16 +135,13 @@ def __init__(self, parent):
         self.connect(self, SIGNAL('itemSelectionChanged()'),
                      self.show_selection)
 
-        self.connect(self,
-                     SIGNAL('itemDoubleClicked(QTreeWidgetItem*,int)'),
+        self.connect(self, SIGNAL('itemDoubleClicked(QTreeWidgetItem*,int)'),
                      self.double_clicked)
 
-        self.connect(self,
-                     SIGNAL('itemCollapsed(QTreeWidgetItem*)'),
+        self.connect(self, SIGNAL('itemCollapsed(QTreeWidgetItem*)'),
                      lambda x: self.update_column_widths())
 
-        self.connect(self,
-                     SIGNAL('itemExpanded(QTreeWidgetItem*)'),
+        self.connect(self, SIGNAL('itemExpanded(QTreeWidgetItem*)'),
                      lambda x: self.update_column_widths())
 
     def add_item(self, txt, hide=False):
@@ -160,9 +158,13 @@ def add_item(self, txt, hide=False):
             self.setItemHidden(item, True)
 
     def restore_selection(self):
+        # clear() generates more callbacks, which we can safely ignore
+        if self.busy:
+            return
         if not self.old_selection or not self.old_contents:
             return
 
+        empty = True
         old_c = self.old_contents
         old_s = self.old_selection
         new_c = self.contents()
@@ -200,8 +202,9 @@ def select(item, current=False):
             category, idx = self.old_current_item
             if category == self.idx_header:
                 item = self.invisibleRootItem().child(idx)
-                self.setCurrentItem(item)
-                self.setItemSelected(item, True)
+                if item is not None:
+                    self.setCurrentItem(item)
+                    self.setItemSelected(item, True)
                 return
             # Reselect the current item
             selection_info = saved_selection[category]
@@ -214,6 +217,7 @@ def select(item, current=False):
                 return
             if item in new:
                 reselect(item, current=True)
+                empty = False
 
         # Restore selection
         # When reselecting we only care that the items are selected;
@@ -224,6 +228,7 @@ def select(item, current=False):
             for item in selection:
                 if item in new:
                     reselect(item, current=False)
+                    empty = False
         self.blockSignals(False)
 
         for (new, old, selection, reselect) in saved_selection:
@@ -245,6 +250,10 @@ def select(item, current=False):
                     if j in new:
                         reselect(j, current=True)
                         return
+        if empty:
+            self.busy = True
+            self.clear()
+            self.busy = False
 
     def restore_scrollbar(self):
         vscroll = self.verticalScrollBar()
@@ -302,6 +311,9 @@ def save_scrollbar(self):
             self.old_scroll = None
 
     def current_item(self):
+        s = self.selected_indexes()
+        if not s:
+            return None
         current = self.currentItem()
         if not current:
             return None
@@ -354,6 +366,7 @@ def _set_subtree(self, items, idx,
                      untracked=False,
                      check=True):
         """Add a list of items to a treewidget item."""
+        self.blockSignals(True)
         parent = self.topLevelItem(idx)
         if items:
             self.setItemHidden(parent, False)
@@ -374,6 +387,7 @@ def _set_subtree(self, items, idx,
                                                untracked=untracked)
             parent.addChild(treeitem)
         self.expand_items(idx, items)
+        self.blockSignals(False)
 
     def update_column_widths(self):
         self.resizeColumnToContents(0)
@@ -777,34 +791,6 @@ def _subtree_selection(self, idx, items):
         item = self.topLevelItem(idx)
         return qtutils.tree_selection(item, items)
 
-    def mouseReleaseEvent(self, event):
-        result = QtGui.QTreeWidget.mouseReleaseEvent(self, event)
-        self.clicked()
-        return result
-
-    def clicked(self, item=None, idx=None):
-        """Called when a repo status tree item is clicked.
-
-        This handles the behavior where clicking on the icon invokes
-        the a context-specific action.
-
-        """
-        # Sync the selection model
-        s = self.selection()
-        cola.selection_model().set_selection(s)
-
-        # Clear the selection if an empty area was clicked
-        selection = self.selected_indexes()
-        if not selection:
-            if self.m.amending():
-                cmds.do(cmds.SetDiffText, '')
-            else:
-                cmds.do(cmds.ResetMode)
-            self.blockSignals(True)
-            self.clearSelection()
-            self.blockSignals(False)
-            return
-
     def double_clicked(self, item, idx):
         """Called when an item is double-clicked in the repo status tree."""
         self._process_selection()
@@ -832,13 +818,21 @@ def _open_parent_dir(self):
         selection = self.selected_group()
         cmds.do(cmds.OpenParentDir, selection)
 
+    def clear(self):
+        if self.m.amending():
+            cmds.do(cmds.SetDiffText, '')
+        else:
+            cmds.do(cmds.ResetMode)
+
     def show_selection(self):
         """Show the selected item."""
         # Sync the selection model
-        cola.selection_model().set_selection(self.selection())
+        s = self.selection()
+        cola.selection_model().set_selection(s)
 
         selection = self.selected_indexes()
         if not selection:
+            self.clear()
             return
         category, idx = selection[0]
         # A header item e.g. 'Staged', 'Modified', etc.