Fix missing and semi-transparent events in oneshot render

[dmitrylyzo]

Changes

• Fix a lost last event
• Fix event tag parsing for correct animation detection
  • \ starts new tag
  • ) completes the tag
  • ; is a generic character (not a delimiter)
  • ignore spaces after the tag: \move (...), \t (...)
  • ignore unclosed parentheses: \move(..., \t(... at the end of override block
    won't work for \t(...\t(...
• Leave transition result after dropping animations
• Fix array comparison

The parser is far from perfect, but I think we need to fix the semi-transparent subtitles issue in our fork until the upstream is ready.

a short review on parser - first sentence.
Looking at the revised “Fix event tag parsing” I can again see more parsing mistakes in the newly touched code (eg using locale-dependent functions, assuming parentheses can be nested, and more).

isalnum and isspace can be replaced with our own, but I see no reason to do this for nearly valid subtitles (which don't use non-Latin characters in override blocks).
I don't know if nested parentheses are ignored, but again, this doesn't harm for valid subtitles.

The upstream goes a different way - it now uses a simplified parser (without analyzing move).

New parser in action

// clear - dropAllAnimations disabled
// drop - dropAllAnimations enabled
// -> 1/0 - animated or not

clear: Move (with tabulator) {\move	(50,50,1230,670)} -> 1
drop:  Move (with tabulator) {                      } -> 0
clear: {\c1&H000000&\alpha&HAA}Move (with unclosed block) {\move(50,50,1230,670) -> 1
drop:  {\c1&H000000&\alpha&HAA}Move (with unclosed block) {                      -> 0
clear: {\notatag \fs50 \t     (\frz180}Transform (with space) -> 1
drop:  {\notatag \fs50         \frz180}Transform (with space) -> 0
clear: {\frz30 aa \fad(100,500) \fs120}Fad simple -> 1
drop:  {\frz30 aa               \fs120}Fad simple -> 0
clear: {\frz-30 b \fade(50,255,0,10,300,700,900) \fs121}Fade complex -> 1
drop:  {\frz-30 b                                \fs121}Fade complex -> 0
clear: いろは{\kf128}笑{\kf47}え{\kf24}ば {\kf91}空{\kf58}ま{\kf27}で -> 1
drop:  いろは{      }笑{     }え{     }ば {     }空{     }ま{     }で -> 0
clear: にほえと{\ko128}笑{\ko47}え{\ko24}ば {\ko91}空{\ko58}ま{\ko27}で -> 1
drop:  にほえと{      }笑{     }え{     }ば {     }空{     }ま{     }で -> 0
clear: ちりぬるを{\K128}笑{\k47}え{\K24}ば {\k91}空{\K58}ま{\k27}で -> 1
drop:  ちりぬるを{     }笑{    }え{    }ば {    }空{    }ま{    }で -> 0
clear: {\shad5\bord5\fnIPAMincho}週間 -> 0
drop:  {\shad5\bord5\fnIPAMincho}週間 -> 0
clear: {\an2}Not animated due to libass ext \{\move(1,1,500,500)} -> 0
drop:  {\an2}Not animated due to libass ext \{\move(1,1,500,500)} -> 0
clear: {\an8}{\bord3}Animated {\move(1,1,500,500)} with unusual{\1c&H00FF00&}ly placed {\r}tags -> 1
drop:  {\an8}{\bord3}Animated {                  } with unusual{\1c&H00FF00&}ly placed {\r}tags -> 0
clear: {\notatag \fs50 \t     (\frz180)}Transform 2 (with space) -> 1
drop:  {\notatag \fs50         \frz180)}Transform 2 (with space) -> 0
clear: {\notatag \fs50 \t     ((\frz180)}Transform 3 (with space) -> 1
drop:  {\notatag \fs50          \frz180)}Transform 3 (with space) -> 0
clear: {\notatag \fs50 \t (500, 2000, \frz180)}Transform 4 (with space) -> 1
drop:  {\notatag \fs50                \frz180)}Transform 4 (with space) -> 0
clear: {\t(0,130,\1c&HFFFFFF&\t(65,565,\fscy0)}Transform 5 -> 1
drop:  {         \1c&HFFFFFF&\t(65,565,\fscy0)}Transform 5 -> 0
clear: {\t(0,120,\1c&H00FFFF&\t\frz180)}Transform 6 -> 1
drop:  {         \1c&H00FFFF&\t\frz180)}Transform 6 -> 0

The animation for Transform 5 is incorrectly dropped (but detected correctly) because \t( starts a new transition (libass#111 (comment)), but the parser is "in brackets". We don't use dropAllAnimations and the old parser didn't detect animation for these samples.

Issues
jellyfin/jellyfin-web#2291
Due to incorrect parsing \fad and \fade are not considered animated and are displayed in a semi-transparent state.

[dmitrylyzo]

Superseded by #24, #26 for the new master branch.