Use integer line-height to avoid rounding differences

[redmunds]

Yet another attempt at #3478.

@iwehrman Can you try this branch to see if it fixes the issue for you?

[iwehrman]

Nailed it!

[redmunds]

@TomMalbran Care to review this one? I updated fix so it doesn't round off em values.

[TomMalbran]

Sure I can.

This looks good and finally fixes the problem, but since we previously increased the line height ratio a lot to avoid rounding it made a big gap on a really big font size between the light backgrounds of 2 consecutive rows. Since we now need to round the value, maybe we could decrease the line height ratio a bit, 1.27 seems to work nicely on Win XP. But with 1.27 the fourth view commands integration test is failing, for a similar problem to the ones fixed. So this test would need to be fixed too.

[redmunds]

I definitely want to fix any gaps, but a ratio of 1.27 seems too weird for me. I tried 1.25 with Math.round() but that didn't fix the original problem. Maybe 1.25 with Math.ceil() will work?

[TomMalbran]

1.25 and ceil seems to be working on Windows... does it work on Mac too?

[redmunds]

@TomMalbran 1.25 and ceil looks good on Mac, both retina and non-retina. I see some gaps if you make font-size super large, but that's not a common workflow.

Chnages pushed. Ready for re-review.

[TomMalbran]

This looks great. I can see some gaps at some big font-sizes but is just a 1px gap, and I don't think we can do nothing about it, but it is a lot less than with the previews line height ratio.

Before merging this I see a failure in the fourth test in view command handlers. Do we need to fix that now or add a new issue for it? It has a similar problem to the other 2 tests, when we switched from 1px updates to line ratios ones. And there is a issue with Travis, with one of the tests, which I am not sure why it is here. Maybe a final merge with master could fix it?

[redmunds]

Sorry, I forgot about the unit test. Pushed a fix.

[peterflynn]

Fwiw -- I have a feeling we'll switch to a different way of highlighting Find results in a month or two anyway, so hopefully the gaps at larger sizes will eventually go away for free...

[TomMalbran]

Great, tests are passing now. Merging.

[redmunds]

Thanks, @TomMalbran !