Preserve current book when doing searches

When doing searches or switching between virtual libraries in the main
book list, preserve the current book. The currently selected book will
remain visible if it is present in the results of the search or the
selected virtual library. Fixes #1216713 [After selecting books which belongs to same serie, when returning to main window, we are at the top of the list and not at previously selected item](https://bugs.launchpad.net/calibre/+bug/1216713)

src/calibre/gui2/library/alternate_views.py

@@ -226,6 +226,7 @@ class AlternateViews(object):
         self.stack = None
         self.break_link = False
         self.main_connected = False
+        self.current_book_state = None
 
     def set_stack(self, stack):
         self.stack = stack
@@ -290,6 +291,15 @@ class AlternateViews(object):
         for view in self.views.itervalues():
             if view is not self.main_view:
                 view.set_context_menu(menu)
+
+    def save_current_book_state(self):
+        self.current_book_state = self.current_view, self.current_view.current_book_state()
+
+    def restore_current_book_state(self):
+        if self.current_book_state is not None:
+            if self.current_book_state[0] is self.current_view:
+                self.current_view.restore_current_book_state(self.current_book_state[1])
+            self.current_book_state = None
 # }}}
 
 # Rendering of covers {{{
@@ -773,4 +783,26 @@ class GridView(QListView):
             sm.select(QItemSelection(top, bottom), sm.Select)
         else:
             return QListView.mousePressEvent(self, ev)
+
+    @property
+    def current_book(self):
+        ci = self.currentIndex()
+        if ci.isValid():
+            try:
+                return self.model().db.data.index_to_id(ci.row())
+            except (IndexError, ValueError, KeyError, TypeError, AttributeError):
+                pass
+
+    def current_book_state(self):
+        return self.current_book
+
+    def restore_current_book_state(self, state):
+        book_id = state
+        try:
+            row = self.model().db.data.id_to_index(book_id)
+        except (IndexError, ValueError, KeyError, TypeError, AttributeError):
+            return
+        self.set_current_row(row)
+        self.select_rows((row,))
+        self.scrollTo(self.model().index(row, 0), self.PositionAtCenter)
 # }}}

src/calibre/gui2/library/models.py

@@ -120,6 +120,7 @@ class BooksModel(QAbstractTableModel):  # {{{
     new_bookdisplay_data = pyqtSignal(object)
     count_changed_signal = pyqtSignal(int)
     searched             = pyqtSignal(object)
+    search_done          = pyqtSignal()
 
     def __init__(self, parent=None, buffer=40):
         QAbstractTableModel.__init__(self, parent)
@@ -392,6 +393,7 @@ class BooksModel(QAbstractTableModel):  # {{{
             # Do not issue search done for the null search. It is used to clear
             # the search and count records for restrictions
             self.searched.emit(True)
+        self.search_done.emit()
 
     def sort(self, col, order, reset=True):
         if not self.db:

src/calibre/gui2/library/views.py

@@ -149,6 +149,7 @@ class BooksView(QTableView):  # {{{
 
     files_dropped = pyqtSignal(object)
     add_column_signal = pyqtSignal()
+    is_library_view = True
 
     def viewportEvent(self, event):
         if (event.type() == event.ToolTip and not gprefs['book_list_tooltips']):
@@ -776,6 +777,28 @@ class BooksView(QTableView):  # {{{
                     self.scrollTo(self.model().index(row, i), self.PositionAtCenter)
                     break
 
+    @property
+    def current_book(self):
+        ci = self.currentIndex()
+        if ci.isValid():
+            try:
+                return self.model().db.data.index_to_id(ci.row())
+            except (IndexError, ValueError, KeyError, TypeError, AttributeError):
+                pass
+
+    def current_book_state(self):
+        return self.current_book, self.horizontalScrollBar().value()
+
+    def restore_current_book_state(self, state):
+        book_id, hpos = state
+        try:
+            row = self.model().db.data.id_to_index(book_id)
+        except (IndexError, ValueError, KeyError, TypeError, AttributeError):
+            return
+        self.set_current_row(row)
+        self.scroll_to_row(row)
+        self.horizontalScrollBar().setValue(hpos)
+
     def set_current_row(self, row=0, select=True, for_sync=False):
         if row > -1 and row < self.model().rowCount(QModelIndex()):
             h = self.horizontalHeader()
@@ -929,18 +952,26 @@ class BooksView(QTableView):  # {{{
             self.select_rows([id_to_select], using_ids=True)
 
     def search_proxy(self, txt):
+        if self.is_library_view:
+            # Save the current book before doing the search, after the search
+            # is completed, this book will become the current book and be
+            # scrolled to if it is present in the search results
+            self.alternate_views.save_current_book_state()
         self._model.search(txt)
         id_to_select = self._model.get_current_highlighted_id()
         if id_to_select is not None:
             self.select_rows([id_to_select], using_ids=True)
         elif self._model.highlight_only:
             self.clearSelection()
+        if self.isVisible():
             self.setFocus(Qt.OtherFocusReason)
 
     def connect_to_search_box(self, sb, search_done):
         sb.search.connect(self.search_proxy)
         self._search_done = search_done
         self._model.searched.connect(self.search_done)
+        if self.is_library_view:
+            self._model.search_done.connect(self.alternate_views.restore_current_book_state)
 
     def connect_to_book_display(self, bd):
         self._model.new_bookdisplay_data.connect(bd)
@@ -955,6 +986,8 @@ class BooksView(QTableView):  # {{{
 
 class DeviceBooksView(BooksView):  # {{{
 
+    is_library_view = False
+
     def __init__(self, parent):
         BooksView.__init__(self, parent, DeviceBooksModel,
                            use_edit_metadata_dialog=False)