I designed a new command. But I found a problem. We have the command [\useinterlinespaceparameter], I thought it would work like \usealignparameter or \usebodyfontparameter, But in the actual testing process, the command does not seem to work at all. % Therefore, I used \dosetupcheckedinterlinespace. In addition, I found that there is also [\useinterlinespaceparameter] in the footnote. it also can't work. Although we can make additional settings through \setups. Or maybe is there something wrong with [\useinterlinespaceparameter]? %%%%%% \unprotect \let\sys_language\language \installnamespace {userlanguage} \installcommandhandler \????userlanguage {userlanguage} \????userlanguage \setupuserlanguage[en][ % interlinespace=, indenting=,] \setupuserlanguage[cn][ % interlinespace=, indenting={yes,2em},] \tolerant\protected\def\userlanguage#*[#1]#*[#2]#*% {\edef\currentuserlanguage{#1}% \ifarguments\or\or \setuplanguage[#1][#2]% \setupuserlanguage[#1][#2]\fi \sys_language[#1]% \ifhmode\else\par \edef\p_language_interlinespace{\userlanguageparameter\c!interlinespace}% \useindentingparameter\userlanguageparameter % \useinterlinespaceparameter\userlanguageparameter% not work \dosetupcheckedinterlinespace\p_language_interlinespace% work \fi \lettonothing\currentuserlanguage} \protect \starttext {\userlanguage[cn]How about \CONTEXT's apostrophes? {\userlanguage[en]How about \CONTEXT's apostrophes?}} {\userlanguage[cn][interlinespace=42pt]\ss\input knuthmath \par} {\userlanguage[en][interlinespace=22pt]\tt\input knuthmath \par} \input knuthmath \stoptext %%%%%%