Accent support progress

[cbreeden]

Accent Support Progress

• If there is no accent, typeset like normal.
• Take largest accent smaller than nucleus.
• Layout nucleus with style cramped.
• Baseline of result == baseline of base.
• Determine offset of accent:
  • Accent has attachment correction:
    • If accentee has attachment correction,
      then align attachment corrections of both.
    • Otherwise, align attachment correction of
      accentee with center of nucleus, plus
      italics correction of nucleus is a symbol.
  • Accent has no attachment correction:
    • If accentee has attachment correction,
      center of accent with accent correction of base.
    • Align accent center with base center (plus)
      italics correction if it's a symbol.
• For superscripts, if accentee is simple symbol,
  scripts should not take accent into account for height. See Accents should not place simple symbols in a ParseNode::Group #4.
• The width of the resulting box is the width of the base.
• BottomAccent: vertical placement is directly below nucleus,
  no correction takes place.
• WideAccent vs Accent: Don't expand non-WideAccent types by default.
• Implement FlattenedAccentBaseHeight.