Add a new printing format to Row_printNanoseconds()

Add a new format: "1.0000ms" - "9.9999ms".
Previously they would print as ".001000s" and ".009999s", and this new
format adds one extra digit of precision.
Note that I print the unit as "ms" rather than microseconds; this saves
code for deciding whether to print the Greek "mu" or the Latin "u".

Row_printNanoseconds() now prints this list of formats:
"     0ns", "999999ns", "1.0000ms", "9.9999ms", ".010000s", ".999999s",
"1.00000s", "59.9999s", "1:00.000", "9:59.999", "10:00.00" ...

Signed-off-by: Kang-Che Sung <[email protected]>

Row.c

@@ -418,6 +418,18 @@ void Row_printNanoseconds(RichString* str, unsigned long long totalNanoseconds,
       return;
    }
 
+   if (totalNanoseconds < 10000000) {
+      // The precision is 0.1 microseconds here.
+      // We print the unit in "ms" rather than microseconds in order
+      // to save the code of choosing the Greek "mu" or Latin "u".
+      uint32_t fraction = (uint32_t)totalNanoseconds / 100;
+      unsigned int milliseconds = (unsigned int)(fraction / 10000);
+      fraction %= 10000;
+      len = xSnprintf(buffer, sizeof(buffer), "%u.%04ums ", milliseconds, (unsigned int)fraction);
+      RichString_appendnAscii(str, baseColor, buffer, len);
+      return;
+   }
+
    unsigned long long totalMicroseconds = totalNanoseconds / 1000;
    unsigned long long totalSeconds = totalMicroseconds / 1000000;
    unsigned long microseconds = totalMicroseconds % 1000000;