In the country that uses non-Latin as the first language, it's very common that strings in xlab and ylab of a plot is in two language, such as Chinese and English.
The font that displays the non-Latin string can not display beautiful latin, especially the space and kern between Latin characters. Thus, it's necessary to set different font face for the Latin and non-Latin strings. In China, we use SimHei to Arial, and SimSun to Times.
However, almost Devices in R can not accept two font faces in a function, such as:
plot(1, type = "n", xlab = "Hello \u4F60\u597D", family = "sans")
Since "sans" can and only can be specific to one font face, e.g., Arial, so "\u4F60\u597D" have to be displayed in a fallback font, such as "SimSun" in a Windows OS. This behavior is even not supported by postscript and PDF Devices.
Therefore, I hope R can support a font fallback that one font family that contains different font, such as:
sans <- c("Arial", "SimHei")
So one character that is not contained in the "Arial" can be displayed in "SimHei".
Thanks in advance.