On Thu, Jun 18, 2020 at 02:05:19AM +1000, Tim Allen wrote: > I discovered recently that if an application running inside st tries to > send a DCS string, subsequent Unicode characters get messed up. For > example, consider the following test-case: > > printf '\303\277\033P\033\\\303\277' > > ...where: > > - \303\277 is the UTF-8 encoding of U+00FF LATIN SMALL LETTER Y WITH > DIAERESIS (ÿ). > - \033P is ESC P, the token that begins a DCS string. > - \033\\ is ESC \, a token that ends a DCS string. > - \303\277 is the same ÿ character again. > > If I run the above command in a VTE-based terminal, or xterm, or > QTerminal, or pterm (PuTTY), I get the output: > > ÿÿ > > ...which is to say, the empty DCS string is ignored. However, if I run > that command inside st (as of commit 9ba7ecf), I get: > > ÿÿ > > ...where those last two characters are \303\277 interpreted as ISO8859-1 > characters, instead of UTF-8. > > I spent some time tracing through the state machines in st.c, and so far > as I can tell, this is how it works currently: > > - ESC P sets the "ESC_DCS" and "ESC_STR" flags, indicating that > incoming bytes should be collected into the strescseq buffer, rather > than being interpreted. > - ESC \ sets the "ESC_STR_END" flag (when ESC is received), and then > calls strhandle() (when \ is received) to interpret the collected > bytes. > - If the collected bytes begin with 'P' (i.e. if this was a DCS > string) strhandle() sets the "ESC_DCS" flag again, confusing the > state machine. > > If my understanding is correct, fixing the problem should be as easy as > removing the line that sets ESC_DCS from strhandle(): > > diff --git a/st.c b/st.c > index ef8abd5..b5b805a 100644 > --- a/st.c > +++ b/st.c > @@ -1897,7 +1897,6 @@ strhandle(void) > xsettitle(strescseq.args[0]); > return; > case 'P': /* DCS -- Device Control String */ > - term.mode |= ESC_DCS; > case '_': /* APC -- Application Program Command */ > case '^': /* PM -- Privacy Message */ > return; > > I've tried the above patch and it fixes my problem, but I don't know if > it introduces any others. >
Hi Tim, Thanks for the detailed report and the patch. It looks good to me and I pushed it to master. -- Kind regards, Hiltjo
