class TermBuf::SgrScanner

• TermBuf::SgrScanner
• Reference
• Object

Overview

Reads the escape sequences an application writes to a cursor and turns the ones about appearance into Style changes.

This is what makes io.print "\e[1mbold\e[0m" set the bold attribute on cells rather than putting escape bytes into them. A cursor marked raw skips it, which is the whole point of that flag: an application that changes style by assigning to Cursor#style pays nothing for a scan that would find nothing.

Sequences that say something a cell cannot hold — cursor movement, screen clearing, anything addressing the terminal rather than the text — are consumed and dropped. Honouring them would mean a second, competing idea of where the cursor is, and the buffer already has one.

The parser is separate from the encoder's SGR writer on purpose. They are each other's inverse, and a spec that ran text through both would pass on a pair of matching mistakes.

Defined in:

termbuf/sgr_scanner.cr

Constant Summary

ATTRIBUTES = {1 => Attributes::Bold, 2 => Attributes::Faint, 3 => Attributes::Italic, 5 => Attributes::SlowBlink, 6 => Attributes::RapidBlink, 7 => Attributes::Reverse, 8 => Attributes::Conceal, 9 => Attributes::Strike, 53 => Attributes::Overline, 73 => Attributes::Superscript, 74 => Attributes::Subscript}

The attributes, by the code that sets and the code that clears each.

CLEARS = {22 => Attributes::Bold | Attributes::Faint, 23 => Attributes::Italic, 25 => Attributes::SlowBlink | Attributes::RapidBlink, 27 => Attributes::Reverse, 28 => Attributes::Conceal, 29 => Attributes::Strike, 55 => Attributes::Overline, 75 => Attributes::Superscript | Attributes::Subscript}

A clearing code often undoes more than one attribute: 22 covers both weights, 25 both blink rates, and 75 both scripts.

Constructors

• .new

Instance Method Summary

• #clear : Nil

  Drops anything held back.

• #pending? : Bool

  Whether an incomplete sequence is being held back.

• #scan(bytes : Bytes, style : Style, &emit : String, Style -> ) : Style

  Feeds bytes in, yielding each run of printable text with the style in force at the time.

Constructor Detail

Instance Method Detail