6 ms·

> Colon is the correct separator there Where would I find this documented and how broadly is it supported? So far, the most exhaustive documentation I've foun

by epage 4y ago

> Colon is the correct separator there Where would I find this documented and how broadly is it supported? So far, the most exhaustive documentation I've found is wikipedia [0], vt100 [2], and wezterm with only wezterm talking about this. I also have not seen `:` handled in the various parsers (e.g. `vte` for alacritty) or generators (e.g. `termcolor`) I've looked at. [0] https://en.wikipedia.org/wiki/ANSI_escape_code https://en.wikipedia.org/wiki/ANSI_escape_code [1] https://vt100.net/emu/dec_ansi_parser https://vt100.net/emu/dec_ansi_parser

follower 4y ago
Okay, it took a little bit of digging but I eventually found more about this via a link from the Wikipedia page. * via <https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h4-Functions-using-CSI-_-ordered-by-the-final-character-lparen-s-rparen:CSI-Ps-@.1C80 https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h4-F...> (search for "CSI Pm m Character Attributes (SGR)"): If 88- or 256-color support is compiled, the following apply: [snip] o The 88- and 256-color support uses subparameters described in ISO-8613-6 for indexed color. ISO-8613-6 also mentions direct color, using a similar scheme. xterm supports that, too. o xterm allows either colons (standard) or semicolons (legacy) to separate the subparameters (but after the first colon, colons must be used). The indexed- and direct-color features are summarized in the FAQ, which explains why semicolon is accepted as a subparameter delimiter: Can I set a color by its number? (This links to <https://invisible-island.net/xterm/xterm.faq.html#color_by_number https://invisible-island.net/xterm/xterm.faq.html#color_by_n...>.) The `ctlseqs` document continues: These ISO-8613-6 controls (marked in ECMA-48 5th edition as "reserved for future standardization") are supported by xterm: [snip example with colons ":"] This variation on ISO-8613-6 is supported for compatibility with KDE konsole: [snip example with semicolons ";"] So, the confusion between use of ";" and ":" separators is because the RGB values are not actually parameters (specified as separated by ";"), rather, the RGB values are subparameters (specified as separated by ":"). [Edit #1] This is covered in more detail by <https://invisible-island.net/xterm/xterm.faq.html#color_by_number https://invisible-island.net/xterm/xterm.faq.html#color_by_n...> (mentioned above): We used semicolon (like other SGR parameters) for separating the R/G/B values in the escape sequence, since a copy of ITU T.416 (ISO-8613-6) which presumably clarified the use of colon for this feature was costly. Using semicolon was incorrect because some applications could expect their parameters to be order-independent. As used for the R/G/B values, that was order-dependent. The relevant information, by the way, is part of ECMA-48 (not ITU T.416, as mentioned in Why only 16 (or 256) colors?). Quoting from section 5.4.2 of ECMA-48, page 12, and adding emphasis (not in the standard): [snip] Of course you will immediately recognize that 03/10 is ASCII colon, and that ISO 8613-6 necessarily refers to the encoding in a parameter sub-string. Or perhaps you will not. :D [snip] Later, in 2012 (patch #282), I extended the parser to accommodate the corrected syntax. The original remains, simply because of its widespread use. As before, it took a few years for other terminal developers to notice and start incorporating the improvement. As of March 2016, not all had finished noticing. [snip] * Going forward (e.g., xterm patch #357), these terminfo building blocks are used in ncurses: * xterm+256color2 is the building-block for standard terminals * xterm+256color is a building-block for nonstandard terminals It's unfortunately seemingly not possible to directly link to the specific text but hopefully that's enough pointers for people to find it themselves. Once again, seems it's amazing that anything works anywhere. :D [Edit #1: Corrected from subparameter separator from "," (which is correct for one of the specs I read but incorrect here) to ":".] [Edit #2: Typo fix.]
- epage 4y ago
  Thanks!
- follower 4y ago
  For the sake of completeness, a couple of updates[0]: (1) With regard to the "03/10 is ASCII colon" comment: the "03/10" form is apparently known as "column-row notation" (or "column-line notation", see https://en.wikipedia.org/wiki/ISO/IEC_2022#Notation_and_nomenclature https://en.wikipedia.org/wiki/ISO/IEC_2022#Notation_and_nome...) and refers to the position of the character in an ASCII table such as: https://en.wikipedia.org/wiki/File:USASCII_code_chart.png https://en.wikipedia.org/wiki/File:USASCII_code_chart.png I actually found a reference (https://dicom.nema.org/medical/dicom/2019d/output/html/part05.html#sect_6.1.1 https://dicom.nema.org/medical/dicom/2019d/output/html/part0...) that explains the notation: "the [US ASCII] value can be calculated as (column * 16) + row, e.g., 01/11 corresponds to the value 27 (1BH) [i.e. 0x1B]." It then notes "The column/row notation is used only within Section 6.1 to simplify any cross referencing with applicable ISO standards." :D A (IMO less effective) description can also be found in ECMA-35 (6th edition; section 5.2 "Code Tables"). (2) A nuance with regard to my "the confusion between use of ';' and ':' separators is because the RGB values are not actually parameters" remark: The ECMA-48 (5th Edition; section 5.4.2) specification (& ISO/IEC 8613-6 / ITU-T Rec. T.416) talks about "parameter string" & "parameter sub-string" rather than "sub-parameter". (Also, the "reserved" values mentioned apparently weren't ever actually specified in a standard; and--as noted elsewhere--the format of the ANSI parameter(s) don't exactly match the ODA (ISO/IEC 8613-6 / ITU-T Rec. T.416) format anyway--see ITU-T Rec. T.416 (1993 E) page 41.) (3) The Wikipedia talk page on ANSI escape codes makes...interesting...reading: https://en.wikipedia.org/wiki/Talk:ANSI_escape_code#Clarification_for_sentence_in_24-bit_colour_section_sought https://en.wikipedia.org/wiki/Talk:ANSI_escape_code#Clarific... [0] i.e. let me inflict this "knowledge" on you. :D [n] The best explanation for how we ended up in this mess is, I think, found in "Figure 6 - Structure of 8-bit codes" of ECMA-35 (6th Edition). :D

by epage 4y ago

follower 4y ago

Okay, it took a little bit of digging but I eventually found more about this via a link from the Wikipedia page. * via <https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h4-Functions-using-CSI-_-ordered-by-the-final-character-lparen-s-rparen:CSI-Ps-@.1C80 https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h4-F...> (search for "CSI Pm m Character Attributes (SGR)"): If 88- or 256-color support is compiled, the following apply: [snip] o The 88- and 256-color support uses subparameters described in ISO-8613-6 for indexed color. ISO-8613-6 also mentions direct color, using a similar scheme. xterm supports that, too. o xterm allows either colons (standard) or semicolons (legacy) to separate the subparameters (but after the first colon, colons must be used). The indexed- and direct-color features are summarized in the FAQ, which explains why semicolon is accepted as a subparameter delimiter: Can I set a color by its number? (This links to <https://invisible-island.net/xterm/xterm.faq.html#color_by_number https://invisible-island.net/xterm/xterm.faq.html#color_by_n...>.) The `ctlseqs` document continues: These ISO-8613-6 controls (marked in ECMA-48 5th edition as "reserved for future standardization") are supported by xterm: [snip example with colons ":"] This variation on ISO-8613-6 is supported for compatibility with KDE konsole: [snip example with semicolons ";"] So, the confusion between use of ";" and ":" separators is because the RGB values are not actually parameters (specified as separated by ";"), rather, the RGB values are subparameters (specified as separated by ":"). [Edit #1] This is covered in more detail by <https://invisible-island.net/xterm/xterm.faq.html#color_by_number https://invisible-island.net/xterm/xterm.faq.html#color_by_n...> (mentioned above): We used semicolon (like other SGR parameters) for separating the R/G/B values in the escape sequence, since a copy of ITU T.416 (ISO-8613-6) which presumably clarified the use of colon for this feature was costly. Using semicolon was incorrect because some applications could expect their parameters to be order-independent. As used for the R/G/B values, that was order-dependent. The relevant information, by the way, is part of ECMA-48 (not ITU T.416, as mentioned in Why only 16 (or 256) colors?). Quoting from section 5.4.2 of ECMA-48, page 12, and adding emphasis (not in the standard): [snip] Of course you will immediately recognize that 03/10 is ASCII colon, and that ISO 8613-6 necessarily refers to the encoding in a parameter sub-string. Or perhaps you will not. :D [snip] Later, in 2012 (patch #282), I extended the parser to accommodate the corrected syntax. The original remains, simply because of its widespread use. As before, it took a few years for other terminal developers to notice and start incorporating the improvement. As of March 2016, not all had finished noticing. [snip] * Going forward (e.g., xterm patch #357), these terminfo building blocks are used in ncurses: * xterm+256color2 is the building-block for standard terminals * xterm+256color is a building-block for nonstandard terminals It's unfortunately seemingly not possible to directly link to the specific text but hopefully that's enough pointers for people to find it themselves. Once again, seems it's amazing that anything works anywhere. :D [Edit #1: Corrected from subparameter separator from "," (which is correct for one of the specs I read but incorrect here) to ":".] [Edit #2: Typo fix.]

epage 4y ago
Thanks!
follower 4y ago
For the sake of completeness, a couple of updates[0]: (1) With regard to the "03/10 is ASCII colon" comment: the "03/10" form is apparently known as "column-row notation" (or "column-line notation", see https://en.wikipedia.org/wiki/ISO/IEC_2022#Notation_and_nomenclature https://en.wikipedia.org/wiki/ISO/IEC_2022#Notation_and_nome...) and refers to the position of the character in an ASCII table such as: https://en.wikipedia.org/wiki/File:USASCII_code_chart.png https://en.wikipedia.org/wiki/File:USASCII_code_chart.png I actually found a reference (https://dicom.nema.org/medical/dicom/2019d/output/html/part05.html#sect_6.1.1 https://dicom.nema.org/medical/dicom/2019d/output/html/part0...) that explains the notation: "the [US ASCII] value can be calculated as (column * 16) + row, e.g., 01/11 corresponds to the value 27 (1BH) [i.e. 0x1B]." It then notes "The column/row notation is used only within Section 6.1 to simplify any cross referencing with applicable ISO standards." :D A (IMO less effective) description can also be found in ECMA-35 (6th edition; section 5.2 "Code Tables"). (2) A nuance with regard to my "the confusion between use of ';' and ':' separators is because the RGB values are not actually parameters" remark: The ECMA-48 (5th Edition; section 5.4.2) specification (& ISO/IEC 8613-6 / ITU-T Rec. T.416) talks about "parameter string" & "parameter sub-string" rather than "sub-parameter". (Also, the "reserved" values mentioned apparently weren't ever actually specified in a standard; and--as noted elsewhere--the format of the ANSI parameter(s) don't exactly match the ODA (ISO/IEC 8613-6 / ITU-T Rec. T.416) format anyway--see ITU-T Rec. T.416 (1993 E) page 41.) (3) The Wikipedia talk page on ANSI escape codes makes...interesting...reading: https://en.wikipedia.org/wiki/Talk:ANSI_escape_code#Clarification_for_sentence_in_24-bit_colour_section_sought https://en.wikipedia.org/wiki/Talk:ANSI_escape_code#Clarific... [0] i.e. let me inflict this "knowledge" on you. :D [n] The best explanation for how we ended up in this mess is, I think, found in "Figure 6 - Structure of 8-bit codes" of ECMA-35 (6th Edition). :D