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12.1 Groups and blocks: delimiter highlighting

Delimiters for groups (<< and >>) and blocks (begin and end) are treated like brackets. Either highlighting of matching group and block delimiters or (group only) blink matching is toggled by the command reduce-show-delim-mode.

REDUCE Show Delim mode is based closely on Show Paren mode; Automatic Display Of Matching Parentheses in The Emacs Editor. It is completely independent except that all settings default to the corresponding values for Show Paren mode. Show Delim mode is turned on automatically when REDUCE mode is selected if reduce-show-delim-mode-on is non-nil, which it is by default if Show Paren mode is on.

Note that highlighting of matching group and block delimiters does not work when point is within a delimiter. (This cannot happen with brackets, which are single characters). This may be changed in future.

M-x reduce-show-delim-mode ¶

Toggle REDUCE Show Delim mode. With a prefix argument, turn REDUCE Show Delim mode on if and only if the argument is positive. When REDUCE Show Delim mode is enabled, any matching delimiter is highlighted after reduce-show-delim-delay seconds of Emacs idle time. See Customization of REDUCE IDE.

Show Delim mode is a buffer-local minor mode. Whenever point is before an opening delimiter or after a closing delimiter, the delimiter, its matching delimiter, and optionally the text between them are highlighted. To customize REDUCE Show Delim mode, type M-x customize-group RET reduce-delim-showing. The customizable options which control the operation of this mode include the following:

• reduce-show-delim-highlight-opendelim controls whether to highlight an opening delimiter when point stands just before it, and hence its position is marked by the cursor anyway. The default is the value of show-paren-highlight-openparen.
• reduce-show-delim-style controls whether just the two delimiters, or also the space between them get highlighted. The valid options here are delimiter (show the matching delimiter), expression (highlight the entire expression enclosed by the delimiters), and mixed (highlight the matching delimiter if it is visible, the expression otherwise). The default is determined by the value of show-paren-style.
• reduce-show-delim-when-point-inside-delim, when non-nil, causes highlighting also when point is immediately inside a delimiter. The default is the value of show-paren-when-point-inside-paren.
• reduce-show-delim-when-point-in-periphery, when non-nil, causes highlighting also when point is in whitespace at the beginning or end of a line, and there is respectively an opening or closing delimiter as the first or last non-whitespace characters on the line. The default is the value of show-paren-when-point-in-periphery.