IIRC xterm-direct uses the : form for RGB colour but xterm-256color does not use it for 256 colours, so for 256 colours you can no doubt get away without it.
As far as SGR 38/48 with anything except 2 and 5 goes - the only terminals I have at hand do not discard but I think either of discarding or not discarding would be reasonable. What does xterm do here? It would probably be best to do the same. On Fri, 6 Jan 2023, 18:42 Crystal Kolipe, <kolip...@exoticsilicon.com> wrote: > On Fri, Jan 06, 2023 at 06:21:41PM +0000, Nicholas Marriott wrote: > > You should strictly only discard the following two arguments or stuff > like > > SGR 38;5;100;1 won't work. > > Well I was initially in two minds about that, because I thought there > might be > other un-official extensions that used 38 with a varying number of > parameters. > > But I haven't found any apart from 5 followed by one argument, and 2 > followed > by three RGB values, so yes I agree with you on this. > > However, since this morning I've been working on actually implementing 256 > colour support so the next version of the patch will parse SGR 38;5 > sequences > correctly. > > Presumably though, if we see SGR 38;X where X is neither 2 nor 5, we still > have to discard everything, right? Because that would be an invalid > sequence > and we don't know for sure whether anything that comes after it is actually > intended as regular control codes or parameters for something else. > > I.E. > > SGR 38;5;X - we set colour X. > SGR 38;2;X;X;X - we discard three parameters, then continue parsing. > SGR 38;Y; - where Y is 'something else', we ignore everything until the > 'm'. > > Or is there a better way? > > Regarding 256 colour support, I've got it working, (on 32bpp displays > only), > but there are two open questions: > > 1. On displays that don't support 256 colours, (e.g. VGA console), what > should > SGR 38;5;X do? I currently have it set so that it selects colours 0-7, > and > for 8-255 just does nothing, (leaves the current colour). > > 2. We implement bold as brighter text rather than a bold font. This > doesn't > work very well with a 256 colour palette. We can't just +8 to get a > bright > version of the colour. How should bold work with arbitrary colours? > > > This is why some people prefer the : form but the ship has rather sailed > on > > that. > > I'm assuming that we don't really need to implement the : form? > > Thanks again for the feedback. >
