Implement stage class as metadata in the karaoke beatmap

[andy840119]

What's will planning:

1. Layout will be the part of metadata in the karaoke beatmap, and will have following type of layouts:

   • Classic -> Current version .
   • Scrolling -> Might appear in the V2.
   • Animation -> Might appear in the V2 or later

2. Not recording time info in the Lyric class because the start time and the end time will be affected by the layout.

   • The start time and end time will not be saved in the layout metadata, or being calculated instead.

3. Re-define the roles:

   • Beatmap: record the supported layout type and it's info.
   • Hit object(Lyric): pure and most importand data, the data field should always useful and will not being replaced if display type changed.
   • Skin: give it an id, and it will return something like texture and shader effect.

[andy840119]

The benefit of change:

• Missing skin in the beatmap will only lost the style. We can use internal or default skin instead.
  • Means less logic in the skin class.
• The data is not separated.
• Easy to design new layout. The current layout will not being affected if create new layout.
• Should be possible to switch the layout by mod.

[andy840119]

Not really sure should use the same mapping role?
And the relationship between lyric and note?

[andy840119]

What's the step to move the layout from skin into beatmap:

• Remove initialize working time in the lyric -> Implemented in the Remove initialize working time in the lyric. #1763.
• Implement classic layout class for the beatmap. -> Implemented in the Implement the base stage info for the beatmap. #1821.
• Should be able to place the layout and lyric config into into hit-object by beatmap processor.
• Make start time and end time as JsonIgnored -> Implemented in the Mark start time and end time as json-ignored in the lyric. #1761.
• Move the apply logic from karaoke skin to:
  1. Drawable class
  2. Layout in the beatmap.
• Remove the logic from the skin.

[andy840119]

Not really sure should rename the "layout" into "stage"?
Because layout info might contain style lookup info.

[andy840119]

Close this issue due to most parts has been implemented.
Lazy to mention all the PRs.