Make drag & drop work again in the tag browser. Fix problem w/Qt near the end of the list.

src/calibre/gui2/tag_browser/model.py

@@ -335,7 +335,6 @@ class TagsModel(QAbstractItemModel): # {{{
                         node.is_gst = is_gst
                         if not is_gst:
                             node.tag.is_hierarchical = '5state'
-                        if not is_gst:
                             tree_root[p] = {}
                             tree_root = tree_root[p]
                     else:
@@ -519,7 +518,7 @@ class TagsModel(QAbstractItemModel): # {{{
                 # category display order is important here. The following works
                 # only if all the non-user categories are displayed before the
                 # user categories
-                if category_is_hierarchical:
+                if category_is_hierarchical or tag.is_hierarchical:
                     components = get_name_components(tag.original_name)
                 else:
                     components = [tag.original_name]
@@ -581,6 +580,14 @@ class TagsModel(QAbstractItemModel): # {{{
                 return [(t.tag.id, t.tag.original_name, t.tag.count)
                         for t in cat.child_tags() if t.tag.count > 0]
 
+    def is_in_user_category(self, index):
+        if not index.isValid():
+            return False
+        p = self.get_node(index)
+        while p.type != TagTreeItem.CATEGORY:
+            p = p.parent
+        return p.tag.category.startswith('@')
+
     # Drag'n Drop {{{
     def mimeTypes(self):
         return ["application/calibre+from_library",
@@ -646,13 +653,13 @@ class TagsModel(QAbstractItemModel): # {{{
         action is Qt.CopyAction or Qt.MoveAction
         '''
         def process_source_node(user_cats, src_parent, src_parent_is_gst,
-                                is_uc, dest_key, node):
+                                is_uc, dest_key, idx):
             '''
             Copy/move an item and all its children to the destination
             '''
             copied = False
-            src_name = node.tag.original_name
-            src_cat = node.tag.category
+            src_name = idx.tag.original_name
+            src_cat = idx.tag.category
             # delete the item if the source is a user category and action is move
             if is_uc and not src_parent_is_gst and src_parent in user_cats and \
                                     action == Qt.MoveAction:
@@ -675,7 +682,7 @@ class TagsModel(QAbstractItemModel): # {{{
             if add_it:
                 user_cats[dest_key].append([src_name, src_cat, 0])
 
-            for c in node.children:
+            for c in idx.children:
                 copied = process_source_node(user_cats, src_parent, src_parent_is_gst,
                                              is_uc, dest_key, c)
             return copied
@@ -696,11 +703,11 @@ class TagsModel(QAbstractItemModel): # {{{
             if dest_key not in user_cats:
                 continue
 
-            node = self.index_for_path(path)
-            if node:
+            idx = self.index_for_path(path)
+            if idx.isValid():
                 process_source_node(user_cats, src_parent, src_parent_is_gst,
                                              is_uc, dest_key,
-                                             self.get_node(node))
+                                             self.get_node(idx))
 
         self.db.prefs.set('user_categories', user_cats)
         self.refresh_required.emit()
@@ -1139,6 +1146,8 @@ class TagsModel(QAbstractItemModel): # {{{
             return QModelIndex()
 
         ans = self.createIndex(parent_item.row(), 0, parent_item)
+        if not ans.isValid():
+            return QModelIndex()
         return ans
 
     def rowCount(self, parent):

src/calibre/gui2/tag_browser/view.py

@@ -12,7 +12,8 @@ from functools import partial
 from itertools import izip
 
 from PyQt4.Qt import (QStyledItemDelegate, Qt, QTreeView, pyqtSignal, QSize,
-        QIcon, QApplication, QMenu, QPoint, QModelIndex, QToolTip, QCursor)
+        QIcon, QApplication, QMenu, QPoint, QModelIndex, QToolTip, QCursor,
+        QDrag)
 
 from calibre.gui2.tag_browser.model import (TagTreeItem, TAG_SEARCH_STATES,
         TagsModel)
@@ -101,6 +102,7 @@ class TagsView(QTreeView): # {{{
         self.setDragEnabled(True)
         self.setDragDropMode(self.DragDrop)
         self.setDropIndicatorShown(True)
+        self.in_drag_drop = False
         self.setAutoExpandDelay(500)
         self.pane_is_visible = False
         self.search_icon = QIcon(I('search.png'))
@@ -232,10 +234,35 @@ class TagsView(QTreeView): # {{{
         s = s if s else None
         self._model.set_search_restriction(s)
 
+    def mouseMoveEvent(self, event):
+        dex = self.indexAt(event.pos())
+        if self.in_drag_drop or not dex.isValid():
+            QTreeView.mouseMoveEvent(self, event)
+            return
+        # Must deal with odd case where the node being dragged is 'virtual',
+        # created to form a hierarchy. We can't really drag this node, but in
+        # addition we can't allow drag recognition to notice going over some
+        # other node and grabbing that one. So we set in_drag_drop to prevent
+        # this from happening, turning it off when the user lifts the button.
+        self.in_drag_drop = True
+        if not self._model.flags(dex) & Qt.ItemIsDragEnabled:
+            QTreeView.mouseMoveEvent(self, event)
+            return
+        md = self._model.mimeData([dex])
+        pixmap = dex.data(Qt.DecorationRole).toPyObject().pixmap(25, 25)
+        drag = QDrag(self)
+        drag.setPixmap(pixmap)
+        drag.setMimeData(md)
+        if self._model.is_in_user_category(dex):
+            drag.exec_(Qt.CopyAction|Qt.MoveAction, Qt.CopyAction)
+        else:
+            drag.exec_(Qt.CopyAction)
+
     def mouseReleaseEvent(self, event):
         # Swallow everything except leftButton so context menus work correctly
-        if event.button() == Qt.LeftButton:
+        if event.button() == Qt.LeftButton or self.in_drag_drop:
             QTreeView.mouseReleaseEvent(self, event)
+            self.in_drag_drop = False
 
     def mouseDoubleClickEvent(self, event):
         # swallow these to avoid toggling and editing at the same time
@@ -639,12 +666,19 @@ class TagsView(QTreeView): # {{{
             self.show_item_at_index(self._model.index_for_path(path), box=box,
                                     position=position)
 
+    def expand_parent(self, idx, depth=0):
+        p = self._model.parent(idx)
+        d = 0
+        if p.isValid():
+            d = self.expand_parent(p, depth+1)
+        if d == 0:
+            self.expand(idx)
+        return d+1
+
     def show_item_at_index(self, idx, box=False,
                            position=QTreeView.PositionAtCenter):
         if idx.isValid() and idx.data(Qt.UserRole).toPyObject() is not self._model.root_item:
-            self.expand(self._model.parent(idx)) # Needed otherwise Qt sometimes segfaults if the
-                                                 # node is buried in a collapsed, off
-                                                 # screen hierarchy
+            self.expand_parent(idx)
             self.setCurrentIndex(idx)
             self.scrollTo(idx, position)
             if box: