The Tree window displays information on all the moves in the database made from the current position. Masks add additional information, and can be imagined as a transparent layer above the Tree that holds data such as commentaries for moves or positions, own evaluations, and ones Opening Repertoir.
They are stored in a Mask file (.stm - Scid Tree Mask) and are independent of any database. That is - once created, a Mask can be used with any database by loading it from the Tree Mask menu.
When a Mask is opened, the display of the Tree window changes. First of all, all moves present in the mask are highlighted in purple. Additionally, nags and markers are shown in front of a move, and Comments concerning the move are shown afterwards. Finally, the current postition may also hold a comment.
The indepencence of Masks from a database make them a very powerful tool for handling opening repertoires. Contrary to the traditional way of opening lines, Masks have the advantage to handle transpositions transparently, simply because they are based on the current positions instead of a line leading to it.
The Tree window has a Mask sub-menu, where Masks are opened or created (as well as other features).
Once a Mask is opened, commentary can be added by right-clicking moves and adding comments/nags/markers (etc, see below).
Whole lines may be marked by holding the Control key down while right-clicking. I.E. - for most operations, all *preceding* moves will be marked this way. The exception is RemoveFromMask, which will remove all *following* moves.
Moves not displayed in the Tree may be added to the Mask via the "Add Move to Mask" context menu.
Don't forget to save the Mask! You will be prompted to do it if you close a Mask that has been modified, or if a Tree Window is closed. The most recent Mask file may be automatically opened via Tree-> Options-> Auto-Load-Mask.
For an opening repertoire , one might consider having two masks, one for White, and one for Black openings.
When using Mask Searches, enabling the Tree Adjust Filter checkbox is recommended.
The Mask Search feature enables searches for commentary, symbols etc. Selecting the Search button displays a list of all positions found in FEN notation, followed by the move in question and commentary if any.
The Mask Display feature shows the current Mask in a line style. Starting at the current position all subsequent moves are sorted into some unfoldable tree to give an overview of the current lines of play - similar to what is found in many repertoire books. Not all information is displayed (e.g. Comments are shorted to fit the display). Additionally, as Masks work on positions rather than move sequences, they may contain loops (ie. transpositions) which can't be properly unfolded in a line wise display. i.e this display may be cut at a certain point.
Setting up a mask can be a tedious task, especially for complex opening repertoires. However, if such a repertoire is available as a Scid Database or a number of PGN games, or lines stored in usual chess games, Scid can use that information to set up suitable Masks automatically.
First of all one has to load the information into a Scid Database. In case the information is already available as a Scid Database this is as easy as opening it. In case a PGN file is use it should be either imported into a Scid Database or one can use the Clipbase to import it temporarily (In which case one should make sure the Clipbase is empty before importing).
The next step is to open the tree for the just opened Scid Database. Then a new Mask should be created or an existing one opened. This function may be used to consolidate serveral bases into a single Mask.
Now, the Mask can be filled automatically with the game content of the database. In this process, comments within the games will be converted to move comments (appending to those existing eventually) in the Mask. NAGs will be added as well. To initiate this process one can chose either Fill with game to fill the Mask with the contents of a single game, or Fill with Database to loop over all games in the database.
Note filling a Mask with an entire base can be quite time consuming.
Note The Mask is filled with all moves till the end of the game including all variations within a game. Therefore, it is sensible to use only bases for this procedure that end the games as soon as the middle game is reached.