Transpose chord lead sheet for #534

[juanotto]

Added mechanism to use transposition in IR_ChordSymbol.

The Chord Lead Sheet and the EasyReader show transposed chord symbols when transposition is active.

Main parts of #534 are done with this.

[juanotto]

BTW this is based on #579, only adds one commit with 6 files modified... pretty small

[jjazzboss]

I did not have time to do a detailed review. But a general feeling. I created the ChordLeadSheetItem (and SongPart) client properties (not serialized with the model) to let the app alter the UI without altering the models itself. This proved in the past to be clean and maintainable. For example all ItemRenderers naturally listen to their ChordLeadSheetItem item model. Listening to the item's client properties is also natural and consistent (IR_ChordSymbol already does it by the way). This makes the impact on renderers simpler. This also avoids to add a dependency to PlaybackSettings for all viewers. In the future this kind of change will happen again: we can not add a new dependency each time.

[jjazzboss]

well it's late in the night, I'm not thinking clearly enough, I'll see this week-end ;-)

[juanotto]

I did not have time to do a detailed review. But a general feeling. I created the ChordLeadSheetItem (and SongPart) client properties (not serialized with the model) to let the app alter the UI without altering the models itself. This proved in the past to be clean and maintainable. For example all ItemRenderers naturally listen to their ChordLeadSheetItem item model. Listening to the item's client properties is also natural and consistent (IR_ChordSymbol already does it by the way). This makes the impact on renderers simpler. This also avoids to add a dependency to PlaybackSettings for all viewers. In the future this kind of change will happen again: we can not add a new dependency each time.

Ohhhh that makes sense! I didn't see the client properties at all to be honest :| I'll try to move it, with a quick scanning it seems good to put the transcription in the properties.

I need to find out where is best update the properties, who has the dependency on PlaybackSettings... ideas welcomed. I'll be doing a bit of that over the weekend too :)

[jjazzboss]

Let's agree first on the design approach before you start making the changes. There are several approaches...

[juanotto]

Closing this in favor of #585