Do you mean add the css style into my theme file(.rstheme) like this?
.pre.r{
line-height: 1em !important;
}
I try it, but it's doesn't work.
I found another css style, it can solve it.
.ace_editor, .rstudio-themes-flat.ace_editor_theme .profvis-flamegraph, .rstudio-themes-flat.ace_editor_theme, .rstudio-themes-flat .ace_editor_theme {
line-height: 1.7 !important;
letter-spacing: 0.5px !important;
}