ensure that spark counts in histogram are visible

[kowey]

When spark counts are printed for each histogram bucket, the black text on blue background can be difficult to read.

Perhaps white text should be used in those cases (keeping black text for when the bars are too small to fit the text in), or the text should systematically be placed above the bars.

[MikolajKonarski]

I'll try with white text and perhaps a white outline around black text, too.

[MikolajKonarski]

I've fixed it (right now only on github, see https://github.com/Mikolaj/ThreadScope/blob/working/WhiteInBars.png). Isn't the white too jarring? The spark counts are an extra bit of info, while the bars height is the main one, so perhaps they draw too much attention? I tried grey, but I don't like the look of it. I didn't try a white outline over black text, but I'm afraid it may catch attention even more. Please reopen if you think I can improve the fix in any way.