Speed up reflow when resizing flamegraphs with a monospace font

[itamarst]

This addresses #256 partially; variable-width fonts aren't addressed.

By having two passes, one for reading attributes and one for writing attributes, we avoid refreshing the screen a bazillion times, as recommended by https://web.dev/avoid-large-complex-layouts-and-layout-thrashing/.

I tested this by rendering the input file attached in one of the comments on #256 and resizing the window, in both Chrome and Firefox, and with both variations of text truncation. On my very fast desktop, with a monospace font the resize is in real-time, and with variable-width font there is a noticeable pause before refresh happens.

Before merging I should probably at least:

• Make known_font_size calculation only happen once
• Add some comments (based on above) explaining why code is structured the way it is

[codecov]

Codecov Report

Base: 90.33% // Head: 90.33% // No change to project coverage 👍

Coverage data is based on head (604c7fe) compared to base (9676e33).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #262   +/-   ##
=======================================
  Coverage   90.33%   90.33%           
=======================================
  Files          19       19           
  Lines        4241     4241           
=======================================
  Hits         3831     3831           
  Misses        410      410           

Impacted Files	Coverage Δ
src/flamegraph/mod.rs	97.94% <100.00%> (ø)

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[itamarst]

See attached files to get a sense of the impact, specifically you should resize the window and notice how responsive refreshes are.
result.zip

[itamarst]

Added zoom() support too, so now the refresh on startup is faster.
result.zip

[jonhoo]

This generally looks good to me, just had a couple of questions

[itamarst]

Given this only addresses monospace fonts, perhaps the default font should be monospace for now?

[jonhoo]

Could you post a screenshot of a decently-busy flamegraph with and without monospace fonts? I'd like to see how much of a detriment it is to the appearance.

Also, would you mind updating the changelog?

[itamarst]

I will update changelog once you decide whether you want to change to monospace by default or not.

[jonhoo]

Yeah, looks reasonable to me — let's update the default!

[jonhoo]

Thanks! Will cut a release once I get a chance.

[jonhoo]

Released as 0.11.12 🎉