post.isFixedPitch

[Finii]

Probably you want the font to be detected as monospaced.

Apart from the missing Panose values

• Set Panose flags #125

the font is not really monospaced, although it could be.
The width of the font is generally 1240.

The most obvious errors in being monospaced are:

.notdef -> width 965

uni2123 -> width 7440 (!!!)

Apart from the wrong width (you could in principle just make the advance width standard and have a very big right side bearing), the glyph itself is questionable (see #51).

All the other non-conforming widths are from the ligatures.

Here a complete list of all glyphs with a differing width (patched the fontforge font generation code):

Running CIDOneWidth(SplineFont)
CIDOneWidth width 965 for glyph '.notdef' (#0)
CIDOneWidth width 3720 for glyph 'hyphen_hyphen_greater' (#1fc)
CIDOneWidth width 2480 for glyph 'hyphen_greater' (#1fd)
CIDOneWidth width 2480 for glyph 'parenleft_asterisk' (#1fe)
CIDOneWidth width 3720 for glyph 'parenleft_asterisk_parenright' (#1ff)
CIDOneWidth width 2480 for glyph 'period_hyphen' (#200)
CIDOneWidth width 2480 for glyph 'period_period' (#201)
CIDOneWidth width 3720 for glyph 'period_period_hyphen' (#202)
CIDOneWidth width 3720 for glyph 'period_period_period' (#203)
CIDOneWidth width 3720 for glyph 'period_period_equal' (#204)
CIDOneWidth width 3720 for glyph 'period_period_less' (#205)
CIDOneWidth width 2480 for glyph 'period_equal' (#206)
CIDOneWidth width 2480 for glyph 'colon_colon' (#207)
CIDOneWidth width 3720 for glyph 'colon_colon_colon' (#208)
CIDOneWidth width 2480 for glyph 'colon_equal' (#209)
CIDOneWidth width 2480 for glyph 'colon_greater' (#20a)
CIDOneWidth width 2480 for glyph 'colon_less' (#20b)
CIDOneWidth width 2480 for glyph 'semicolon_semicolon' (#20c)
CIDOneWidth width 2480 for glyph 'exclam_exclam' (#20d)
CIDOneWidth width 2480 for glyph 'exclam_equal' (#20e)
CIDOneWidth width 3720 for glyph 'exclam_equal_equal' (#20f)
CIDOneWidth width 2480 for glyph 'exclam_asciitilde' (#210)
CIDOneWidth width 2480 for glyph 'question_period' (#211)
CIDOneWidth width 2480 for glyph 'question_colon' (#212)
CIDOneWidth width 2480 for glyph 'question_question' (#213)
CIDOneWidth width 2480 for glyph 'asterisk_parenright' (#214)
CIDOneWidth width 3720 for glyph 'asterisk_asterisk_asterisk' (#215)
CIDOneWidth width 2480 for glyph 'asterisk_slash' (#216)
CIDOneWidth width 2480 for glyph 'numbersign_numbersign' (#217)
CIDOneWidth width 3720 for glyph 'numbersign_numbersign_numbersign' (#218)
CIDOneWidth width 2480 for glyph 'numbersign_equal' (#219)
CIDOneWidth width 2480 for glyph 'slash_asterisk' (#21a)
CIDOneWidth width 3720 for glyph 'slash_asterisk_slash' (#21b)
CIDOneWidth width 2480 for glyph 'slash_equal' (#21c)
CIDOneWidth width 3720 for glyph 'slash_equal_equal' (#21d)
CIDOneWidth width 2480 for glyph 'slash_greater' (#21e)
CIDOneWidth width 2480 for glyph 'slash_slash' (#21f)
CIDOneWidth width 3720 for glyph 'slash_slash_slash' (#220)
CIDOneWidth width 2480 for glyph 'slash_backslash' (#221)
CIDOneWidth width 2480 for glyph 'backslash_slash' (#222)
CIDOneWidth width 2480 for glyph 'ampersand_ampersand' (#250)
CIDOneWidth width 2480 for glyph 'bar_bar' (#251)
CIDOneWidth width 2480 for glyph 'bar_greater' (#252)
CIDOneWidth width 2480 for glyph 'equal_colon' (#253)
CIDOneWidth width 3720 for glyph 'equal_colon_equal' (#254)
CIDOneWidth width 3720 for glyph 'equal_exclam_equal' (#255)
CIDOneWidth width 2480 for glyph 'equal_equal' (#256)
CIDOneWidth width 3720 for glyph 'equal_equal_equal' (#257)
CIDOneWidth width 2480 for glyph 'equal_greater' (#258)
CIDOneWidth width 2480 for glyph 'equal_asciitilde' (#259)
CIDOneWidth width 3720 for glyph 'equal_slash_equal' (#25a)
CIDOneWidth width 2480 for glyph 'greater_colon' (#25b)
CIDOneWidth width 2480 for glyph 'greater_equal' (#25c)
CIDOneWidth width 2480 for glyph 'less_hyphen' (#25d)
CIDOneWidth width 2480 for glyph 'less_colon' (#25e)
CIDOneWidth width 4960 for glyph 'less_exclam_hyphen_hyphen' (#25f)
CIDOneWidth width 2480 for glyph 'less_bar' (#260)
CIDOneWidth width 2480 for glyph 'less_equal' (#261)
CIDOneWidth width 2480 for glyph 'less_asciitilde' (#262)
CIDOneWidth width 3720 for glyph 'less_asciitilde_greater' (#263)
CIDOneWidth width 3720 for glyph 'less_asciitilde_asciitilde' (#264)
CIDOneWidth width 2480 for glyph 'less_slash' (#265)
CIDOneWidth width 3720 for glyph 'less_slash_greater' (#266)
CIDOneWidth width 2480 for glyph 'asciitilde_greater' (#267)
CIDOneWidth width 2480 for glyph 'asciitilde_asciitilde' (#268)
CIDOneWidth width 3720 for glyph 'asciitilde_asciitilde_greater' (#269)
CIDOneWidth width 7440 for glyph 'uni2123' (#278)
CIDOneWidth width 0 for glyph 'uni0308' (#2e3)
CIDOneWidth width 0 for glyph 'uni0307' (#2e4)
CIDOneWidth width 0 for glyph 'gravecomb' (#2e5)
CIDOneWidth width 0 for glyph 'acutecomb' (#2e6)
CIDOneWidth width 0 for glyph 'uni030B' (#2e7)
CIDOneWidth width 0 for glyph 'uni030C.alt' (#2e8)
CIDOneWidth width 0 for glyph 'uni0302' (#2e9)
CIDOneWidth width 0 for glyph 'uni030C' (#2ea)
CIDOneWidth width 0 for glyph 'uni0306' (#2eb)
CIDOneWidth width 0 for glyph 'uni030A' (#2ec)
CIDOneWidth width 0 for glyph 'tildecomb' (#2ed)
CIDOneWidth width 0 for glyph 'uni0304' (#2ee)
CIDOneWidth width 0 for glyph 'dotbelowcomb' (#2ef)
CIDOneWidth width 0 for glyph 'uni0326' (#2f0)
CIDOneWidth width 0 for glyph 'uni0327' (#2f1)
CIDOneWidth width 0 for glyph 'uni0328' (#2f2)
CIDOneWidth width 0 for glyph 'uni0308.case' (#2f3)
CIDOneWidth width 0 for glyph 'uni0307.case' (#2f4)
CIDOneWidth width 0 for glyph 'gravecomb.case' (#2f5)
CIDOneWidth width 0 for glyph 'acutecomb.case' (#2f6)
CIDOneWidth width 0 for glyph 'uni030B.case' (#2f7)
CIDOneWidth width 0 for glyph 'uni0302.case' (#2f8)
CIDOneWidth width 0 for glyph 'uni030C.case' (#2f9)
CIDOneWidth width 0 for glyph 'uni0306.case' (#2fa)
CIDOneWidth width 0 for glyph 'uni030A.case' (#2fb)
CIDOneWidth width 0 for glyph 'tildecomb.case' (#2fc)
CIDOneWidth width 0 for glyph 'uni0304.case' (#2fd)

The ligatures substitute multiple 1240 wide glyphs with one extrawide liga glyph.
That could also be formulated differently, so that the ligature glyph itself has the standard width but a
wide right side bearing, here a comparison for example with Cascadia:

They substitude ( and * by parenleft-asterix.liga and LIG, where both parenleft-asterix.liga and LIG are of standard width, LIG is just empty.
You have a different approach. I'm not sure what is better; most fonts I have examined have the 'all glyphs have the same width' approach. At least with that approach it gets isFixedPitch set.

[Finii]

Ah, another downside of the way the ligs are formulated here (substitude two glyphs to one glyph with increased width) is

• Some ligatures render in VSCode as a single letter stop #115

Changing the ligature formulation would probably solve both (but I feel the pain in reformulating the ligs).

[idan]

Split off the notdef glyph width into #159

[idan]

Fixed in ca8015b