_zsh_highlight_internal

# Update ZLE buffer syntax highlighting.
#
# Invokes each highlighter that needs updating.
# This function is supposed to be called whenever the ZLE state changes.
_zsh_highlight_internal()
{
  emulate -L zsh
  setopt localoptions warncreateglobal nobashrematch
  local REPLY # don't leak $REPLY into global scope

  # Do not highlight if there are more than 300 chars in the buffer. It's most
  # likely a pasted command or a huge list of files in that case..
  [[ -n ${ZSH_HIGHLIGHT_MAXLENGTH:-} ]] && [[ $#BUFFER -gt $ZSH_HIGHLIGHT_MAXLENGTH ]] && return

  # Do not highlight if there are pending inputs (copy/paste).
  [[ $PENDING -gt 0 ]] && return

  {
    local cache_place
    local -a region_highlight_copy

    # Select which highlighters in ZSH_HIGHLIGHT_HIGHLIGHTERS need to be invoked.
    local highlighter; for highlighter in $ZSH_HIGHLIGHT_HIGHLIGHTERS; do

      # eval cache place for current highlighter and prepare it
      cache_place="_zsh_highlight__highlighter_${highlighter}_cache"
      typeset -ga ${cache_place}

      # If highlighter needs to be invoked
      if ! type "_zsh_highlight_highlighter_${highlighter}_predicate" >&/dev/null; then
        echo "zsh-syntax-highlighting: warning: disabling the ${(qq)highlighter} highlighter as it has not been loaded" >&2
        # TODO: use ${(b)} rather than ${(q)} if supported
        ZSH_HIGHLIGHT_HIGHLIGHTERS=( ${ZSH_HIGHLIGHT_HIGHLIGHTERS:#${highlighter}} )
      elif "_zsh_highlight_highlighter_${highlighter}_predicate"; then

        # save a copy, and cleanup region_highlight
        region_highlight_copy=("${region_highlight[@]}")
        region_highlight=()

        # Execute highlighter and save result
        {
          "_zsh_highlight_highlighter_${highlighter}_paint"
        } always {
          : ${(AP)cache_place::="${region_highlight[@]}"}
        }

        # Restore saved region_highlight
        region_highlight=("${region_highlight_copy[@]}")

      fi

      # Use value form cache if any cached
      region_highlight+=("${(@P)cache_place}")

    done

    # Re-apply zle_highlight settings

    # region
    () {
      (( REGION_ACTIVE )) || return
      integer min max
      if (( MARK > CURSOR )) ; then
        min=$CURSOR max=$MARK
      else
        min=$MARK max=$CURSOR
      fi
      if (( REGION_ACTIVE == 1 )); then
        [[ $KEYMAP = vicmd ]] && (( max++ ))
      elif (( REGION_ACTIVE == 2 )); then
        local needle=$'\n'
        # CURSOR and MARK are 0 indexed between letters like region_highlight
        # Do not include the newline in the highlight
        (( min = ${BUFFER[(Ib:min:)$needle]} ))
        (( max = ${BUFFER[(ib:max:)$needle]} - 1 ))
      fi
      _zsh_highlight_apply_zle_highlight region standout "$min" "$max"
    }

    # yank / paste (zsh-5.1.1 and newer)
    (( $+YANK_ACTIVE )) && (( YANK_ACTIVE )) && _zsh_highlight_apply_zle_highlight paste standout "$YANK_START" "$YANK_END"

    # isearch
    (( $+ISEARCHMATCH_ACTIVE )) && (( ISEARCHMATCH_ACTIVE )) && _zsh_highlight_apply_zle_highlight isearch underline "$ISEARCHMATCH_START" "$ISEARCHMATCH_END"

    # suffix
    (( $+SUFFIX_ACTIVE )) && (( SUFFIX_ACTIVE )) && _zsh_highlight_apply_zle_highlight suffix bold "$SUFFIX_START" "$SUFFIX_END"

  } always {
    typeset -g _ZSH_HIGHLIGHT_PRIOR_BUFFER="$BUFFER"
    typeset -gi _ZSH_HIGHLIGHT_PRIOR_CURSOR=$CURSOR
  }
}

# Apply highlighting based on entries in the zle_highlight array.
# This function takes four arguments:
# 1. The exact entry (no patterns) in the zle_highlight array:
#    region, paste, isearch, or suffix
# 2. The default highlighting that should be applied if the entry is unset
# 3. and 4. Two integer values describing the beginning and end of the
#    range. The order does not matter.
_zsh_highlight_apply_zle_highlight() {
  local entry="$1" default="$2"
  integer first="$3" second="$4"

  # read the relevant entry from zle_highlight
  #
  # ### In zsh≥5.0.8 we'd use ${(b)entry}, but we support older zsh's, so we don't
  # ### add (b).  The only effect is on the failure mode for callers that violate
  # ### the precondition.
  local region="${zle_highlight[(r)${entry}:*]-}"

  if [[ -z "$region" ]]; then
    # entry not specified at all, use default value
    region=$default
  else
    # strip prefix
    region="${region#${entry}:}"

    # no highlighting when set to the empty string or to 'none'
    if [[ -z "$region" ]] || [[ "$region" == none ]]; then
      return
    fi
  fi

  integer start end
  if (( first < second )); then
    start=$first end=$second
  else
    start=$second end=$first
  fi
  region_highlight+=("$start $end $region, memo=zsh-syntax-highlighting")
}

_zsh_highlight_internal "$@"