OSC 60 Query Allowed Features

Several of xterm’s features are switched on or off by resources, because they could be abused by anything written to the terminal: colors, fonts, the mouse, pasting controls, termcap queries, titles, and window operations. Each has an allow… resource, and a disallowed… list of the parts of it refused while the allow… resource is off. XTQALLOWED, OSC 60 ST, asks which allow… resources are on, and is answered OSC 60 ; list ST with their names separated by commas (report_allowed_ops). It takes no ; and nothing after it; with something there, it is ignored. OSC 61 asks which parts of a feature are refused, and OSC 62 which parts it has.

In a default xterm, allowColorOps, allowFontOps, allowMouseOps, allowTcapOps and allowTitleOps are on, and allowPasteControls and allowWindowOps off. The cases follow it.

Contour’s font settings. Contour uses OSC 60 for something else: its Query or Change Font Settings, read at commit b7caade, which it puts forward as a better OSC 50. OSC 60 ST asks for the fonts, the same bytes as xterm’s query, and

OSC 60 ; size ; regular ; bold ; italic ; bold italic ST

changes them. The specification gives no more than those two lines. In Contour itself, at release 0.8.0, the answer has a sixth field, the emoji font, and the size is in hundredths of a point, so 1200 is 12 points (setAllFont). Each font is a font description, such as Fira Code. When changing them, an empty field, or a size of 0, leaves that setting as it was, and auto for a styled face or the emoji font takes it from the regular font. A change is not made until the user allows it: Contour’s change_font permission is ask by default, and can be set to allow or deny (TerminalSession::setFontDef). A program sending OSC 60 ST cannot tell from the request which of the two it will get back; the answer’s second field, a number in Contour’s and a resource name in xterm’s, tells them apart. xterm ignores the longer form, as it does any OSC 60 with something after it.

This is xterm’s own, and libghostty-vt does not have it, so the case that asks is a known difference. libghostty-vt ignores Contour’s form too: fonts are its host’s business.

Support

Validation

OSC60-1: Which features are allowed

\e]60\a

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reply \e]60;allowColorOps,allowFontOps,allowMouseOps,allowTcapOps,allowTitleOps\a

OSC60-2: Contour’s font settings are ignored

A
\e]60;1200;Fira Code\a
B

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cursor 1,3
reply none