Optimizations for TextView

[urandom]

Only clear the index when the textview dimensions change or the text
itself is cleared.
Add to the index when new text is added to the view.

Fixes #266

[tslocum]

I've created benchmarks for writing to and drawing TextViews (submitted as #356) and compared the results before and after applying these optimizations.

---

go test -run=NONE -bench=. -count=3

Before

After

---

benchcmp -best -changed

Comparison

[Bios-Marcel]

So, it has gotten worse? Because after shows more ns/operation and such

[tslocum]

Based on the benchmark results, these optimizations:

• Increase the amount of time it takes to write to unwrapped TextViews by 350%
• Do not affect the amount of time it takes to write to wrapped TextViews
• Increase the number of allocations when writing to both unwrapped and wrapped TextViews by 1000%
• Increase the allocation size when writing to unwrapped TextViews by 500%
• Do not affect the allocation size of writing to wrapped TextViews
• Reduce the amount of time it takes to draw unwrapped TextViews by 65%
• Reduce the amount of time it takes to draw wrapped TextViews by 20%
• Reduce the allocation size when drawing unwrapped TextViews by 40%
• Reduce the allocation size when drawing wrapped TextViews by 20%

[urandom]

This change optimizes for large amounts of text, especially one that constantly gets appended to (displaying a tailing log).
Your benchmarks present a static text of 512 bytes, where performance is quite insignificant.

[tslocum]

Thanks for your feedback. I've updated the tests and benchmarks to include cases where a small amount of data is written to a TextView that contains a lot of data. You can see these changes in the updated pull request I linked earlier.

Updated results and comparison

[foxcpp]

Any chance to have this merged? I am currently using tview for TUI for my experimental chat application and use TextView as a chat log.

[foxcpp]

@tslocum, hey, since you are maintaining cview, what do you think about getting that PR in? Imo this is a good improvement. I would submit it but there are some non-trivial conflicts so I am not sure about them.

[foxcpp]

I rebased it here: https://github.com/foxcpp/tview/tree/textview-opts but as I said, I am not sure if I did everything correctly.
Also included my small optimization from #435.

[tslocum]

Thanks @foxcpp. I am interested in merging your changes into cview. I'll let you know once I've had a chance to review your changes.

[tslocum]

Hey @foxcpp, I only see your optimization to use TrimRightFunc in your updated branches. Were you able to review the benchmark results which seem to show these changes cause decreases in performance?

[foxcpp]

@tslocum Woops, forgot to git push. Now it should be there. Also added your benchmarks.

Here is the benchcmp output master vs textview-opts branch: benchcmp.txt

There is a decrease in performance for Draw almost everywhere, enough to nullify my TrimRightFunc change, huh. Write gets +500% improvement for scrollable TextView, though.

[tslocum]

I believe you have the results backwards: when not wrapping text, Draw is improved 60% while Write is up to 600% slower (if old is master and new is textview-opts).

[foxcpp]

Woops x2. You are right.

[rivo]

Closing this as it's obsolete. Check out the new TextView implementation for details.