Improved Excerptsdialog

In the future it should be possible to have parts for every single voice in your score, so the idea is, that you can have a main score with SATB and piano with S, A, T and B in one stave and one excerpt with SA-TB, S and A in one staff and T and B in another and another excerpt with every voice in a single excerpt.

To achieve this, a new layout for the excerptsdialog is needed. So let us collect, what we could and should be able to do:

GUI

1. We want to have a simple use for the current behavior (add instruments to a excerpt)
2. We want to select the voices which should be used and showed for every instrument in a part
3. We want to have the same instrument twice in one excerpt (but probably with different voices)

So the new GUI could look like this:
(sorry for the bad picture, but it shows all the necessary things)

It looks a bit like the Instrumentdialog, and in fact, it is used in the excerptsdialog.

On the left, we have the currently existing parts with a delete, a new all and a new button.
In the middle we have the available instruments, in the end without a tree structure, but maybe some additional buttons. We can select then an Instrument and add it to the part or create a new one.
On the right we have the instrumentlist for the selected part and here there will be a tree structure, so we can additionally select the voices we want to use.

With this GUI all cases could be handled, a disadvantage would be, that it's a bit more difficult to use, but the actual one does not allow to add the same instrument two times.

Implementation

The implementation is quite difficult.

The main attribute of a part is, that it is linked to the score, so changes in a part are also changing the main score. So to have the newly created parts linked to the score, but only show some voices, there are at least two possibilities.

1. We could do something like the linked staffs which already exist for voices again, so we could easily select voices and copy them into a stave of a part. But there will be some problems if the voice has gaps, etc. Another problem is, that this is quite a big task and is different from the actual part creation.

2. We add an attribute for each stave of a created part, which stores the selected voices (the voices you want to extract from the stave in the main score). If all voices are selected, all voices are shown and you can select all voices. If there is only one voice selected the other voices should be hidden, but it is not enough to make them invisible, because we would then still be able to change (or even see) the other voices.

For the GSoC project I chose the second possibility, because it uses the actual implementation best.
But we'll have to make some changes in the layout function to hide every new entry in another part or score and think about how we can make a voice completely unselectable. Another problem will be that we can make a gap in voices except voice 1, which means we can erase a rest, so maybe a part would look like the following:

Another problem could be to export the score to Capella or something else, because we have to convert the attribute for which voices of an instrument are used in a part to the corresponding in Capella (if it exists).

If you have an idea how I could deal with the problems I mentioned, don't hesitate to get in contact with me!