Edit Book: When dragging and dropping files to re-order them in the file browser, fix the final order being dependent on the order the files were selected in. Fixes #1440598 [Edit Book: Inverted order of files after drag and drop](https://bugs.launchpad.net/calibre/+bug/1440598)

src/calibre/gui2/tweak_book/file_list.py

@@ -155,6 +155,7 @@ class FileList(QTreeWidget):
 
     def __init__(self, parent=None):
         QTreeWidget.__init__(self, parent)
+        self.ordered_selected_indexes = False
         pi = plugins['progress_indicator'][0]
         if hasattr(pi, 'set_no_activate_on_click'):
             pi.set_no_activate_on_click(self)
@@ -556,7 +557,22 @@ class FileList(QTreeWidget):
             b.setValue(b.minimum())
             QTimer.singleShot(0, lambda : b.setValue(b.maximum()))
 
+    def __enter__(self):
+        self.ordered_selected_indexes = True
+
+    def __exit__(self, *args):
+        self.ordered_selected_indexes = False
+
+    def selectedIndexes(self):
+        ans = QTreeWidget.selectedIndexes(self)
+        if self.ordered_selected_indexes:
+            # The reverse is needed because Qt's implementation of dropEvent
+            # reverses the selectedIndexes when dropping.
+            ans = list(sorted(ans, key=lambda idx:idx.row(), reverse=True))
+        return ans
+
     def dropEvent(self, event):
+        with self:
             text = self.categories['text']
             pre_drop_order = {text.child(i):i for i in xrange(text.childCount())}
             super(FileList, self).dropEvent(event)