Bookmarks: Improve behavior of "Previous Bookmark"

If the text cursor is currently not at the "current bookmark", it is
more intuitive and useful if "Previous Bookmark" first moves to the
current bookmark, instead of jumping to the one before that.
That solves two issues:
- creating a bookmark, jumping somewhere else, and then going back to
  that bookmark
- deleting a bookmark, and then going to the previous one

Task-number: QTCREATORBUG-20061
Change-Id: I6dbb8c94f4d50ae4cc36e52808029e685be11069
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/bookmarks/bookmarkmanager.cpp

@@ -603,7 +603,8 @@ void BookmarkManager::prev()
     QModelIndex current = selectionModel()->currentIndex();
     if (!current.isValid())
         return;
-
+    if (!isAtCurrentBookmark() && gotoBookmark(bookmarkForIndex(current)))
+        return;
     int row = current.row();
     while (true) {
         if (row == 0)
@@ -806,6 +807,17 @@ void BookmarkManager::loadBookmarks()
     updateActionStatus();
 }
 
+bool BookmarkManager::isAtCurrentBookmark() const
+{
+    Bookmark *bk = bookmarkForIndex(selectionModel()->currentIndex());
+    if (!bk)
+        return true;
+    IEditor *currentEditor = EditorManager::currentEditor();
+    return currentEditor
+           && currentEditor->document()->filePath() == Utils::FileName::fromString(bk->fileName())
+           && currentEditor->currentLine() == bk->lineNumber();
+}
+
 // BookmarkViewFactory
 
 BookmarkViewFactory::BookmarkViewFactory(BookmarkManager *bm)

src/plugins/bookmarks/bookmarkmanager.h

@@ -105,6 +105,7 @@ signals:
 private:
     void updateActionStatus();
     void loadBookmarks();
+    bool isAtCurrentBookmark() const;
 
     void documentPrevNext(bool next);