In some engraving styles (mainly jazz), a double system initial bar line is used at structural articulations of the piece.
The PR supports this style, by adding a `_systemInitialBarLineStyle` variable to the `Measure` class which controls the style of the system bar line when the measure is the first of the system and by default it is set to NORMAL. This variable is not accessed directly; rather it is controlled by manipulating the system bar line. A system bar line can be edited:
- by dropping on it a bar line style from the palette (structural styles, like any repeat or END are ignored);
- by selecting it and double clicking a bar line style from the palette (same note as above).
It can be reset:
- by undo;
- by dropping on it (or selecting and double clicking) a NORMAL bar line style from the palette;
- by selecting and deleting it.
As the system bar line style is stored in the measure, if the first measure of a system changes (because of some other editing), the system bar line style will follow accordingly.
There are some inconsistencies in the current management of bar line `_generated` flag and user-modified type:
- Bar lines created by the New Score Wizard are flagged as non-generated, as well as bar lines of measures manually **appended** by the user, while bar lines of measures **inserted** are flagged as generated.
- If a generated bar line is individually changed of typed, it remains flagged as generated, it is not saved and the change is lost upon saving and re-loading.
- The management of the internal flag `BarLine::_customSubtype` is not always consistent.
- The `Measure::_endBarLineGenerated` flag was not always restored properly by undo.
This PR introduces the following fixes:
- The `_generated` flag is consistently used for bar lines whose type can be reconstructed from the context and then do not need to be saved to the output file.
- Normal bar lines are **always** created as generated: initially created by the Wizard, manually appended or inserted.
- Bar lines with custom type (i.e. different from the type which can be expected according to the bar line context) are always flagged as non-generated, ensuring the custom type is written to the output file.
- The `Measure::_endBarLineGenerated` flag is stored by `ChangeEndBarLineType()` and restore upon undo.
- Some test reference scores, based on the inconsistent bar line `_generated` flag, have been uniformed.
Notes:
- Tests about measure (and then bar line) appending, inserting and relative undo's are already included in the `tst_parts` test suite.
- Some inconsistencies remain in the management of custom bar line span and of system-initial bar lines: for the sake of simplicity, they will be dealt with in separate PR's.
- Selecting a built-in span type updates other span values
- Added a check function enforcing correctness and consistency of span data (Span, From, To); it also set spin box mins and maxes to avoid meaningless values (like From below To and so on)
- Removed array of built-in span type data; span type are different enough to make a table useless: ad-hoc code is needed for most of them.
- Removed legacy, commented-out code
- Set mins for span value spins in .ui
- A few typos here and there
**Inspector**
- Align span combo item names with palette names
- Add a [Custom] span item: it is informative only, cannot be selected and is set by the Inspector for spans which do not match any built-in span
- Implement proper selection of span combo item when a bar line is selected in the score
- Enable/disable type combo items according to bar line type (repeats cannot be turned on/off for individual bar lines)
- Implement spanTypeActivated() to set in the score the span selected in the Inspector
**Palette**
- Labels for styles and spans made clearer (hopefully...)
