Function XPLMDrawString 

pub unsafe extern "C" fn XPLMDrawString(
    inColorRGB: *mut f32,
    inXOffset: c_int,
    inYOffset: c_int,
    inChar: *const c_char,
    inWordWrapWidth: *mut c_int,
    inFontID: XPLMFontID,
)

XPLMDrawString

This routine draws a NULL terminated string in a given font. Pass in the lower left pixel that the character is to be drawn onto. Also pass the character and font ID. This function returns the x offset plus the width of all drawn characters. The color to draw in is specified as a pointer to an array of three floating point colors, representing RGB intensities from 0.0 to 1.0.