Implement text editor DOM updates manually instead of via React

[nathansobo]

React is an amazing abstraction, but very few abstractions come without at least some overhead. In the case of Atom's text editor, it's worth the effort to avoid this overhead by hand coding all DOM updates. The update code is repetitive, but it's also pretty straightforward. In exchange, we get much simpler profile traces, drop a big dependency, and reduce the overall number of moving parts in Atom. Below are some flame graphs for entering a character at the end of a syntax-highlighted line. The comparison is somewhat unfair because the React case could have been a bit more optimized, but I think the pictures also show how much simpler the manual approach is in our case.

React is a great tool for many cases, for our particular needs in this particular case I decided it would be easier to just do things for ourselves.

Remaining Tasks:

• Don't use React for EditorComponent
• Fix autocomplete spec.
• Unify DOM updates / polling across editors.

[benogle]

Legit

[nathansobo]

I'm going to keep the basic structure of the code with the TextEditorComponent separate from the TextEditorElement the same for now. It might be nice to clean it up but it's not really a huge deal and I think time could be spent better in other ways. Someday I would love to get to a more minimal DOM structure as well, but it doesn't seem worth the risk of breaking anything to lose a couple extra nodes.

[lee-dohm]

@nathansobo I've been working with it for the past hour. I haven't noticed any issues. But it does seem a bit more responsive 😀

[thomasjo]

Been using this all day and haven't noticed any regressions. The constant console logging is very annoying though, hehe 👼

[thomasjo]

I've not really noticed any major performance issues in the past few months, so hard to tell whether the speedup is noticeable or not on my machine, but things do seem a bit more responsive. Could be confirmation bias though.

[postcasio]

Same here. No issues so far, playing well with my other packages. Scrolling is silky smooth!

[as-cii]

Same here, it has been working fine so far. Great job, @nathansobo! 👍

[nathansobo]

Thanks to all of you for your time! @thomasjo thanks for pointing out the console logging. I accidentally left it in on the last commit and just force-pushed an amendment.

[kevinsawicki]

📈 💚 ♻️

[lee-dohm]

👏 Awesome work!

[nathansobo]

I force pushed back the merge of this PR so we can get a release out this morning without me having to worry about this code over the weekend. Will merge it again once the release is out.

[kevinsawicki]

Might want to return after this line to prevent array return.

[nathansobo]

👍 Very good catch.

[nathansobo]

Okay, merged in 9648093. Sorry for the false 🚨.

[hemanth]

Interesting stats, but was curious about why was react opted before...

[nathansobo]

@hemanth There was also a huge improvement over the first version of the editor when we added React. It was much like scaffolding.

[hemanth]

👍

[mcharytoniuk]

Why didn't you use React's PureRenderMixin (http://facebook.github.io/react/docs/pure-render-mixin.html), 'shouldComponentUpdate' custom implementation, batched updates and other optimisations that would produce better results than manual updates and abandoned the entire solution rapidly instead?

[kl3ryk]

@mcharytoniuk +1

[benogle]

@mcharytoniuk The old implementation was doing the same thing as described in the doc page:

Under the hood, the mixin implements shouldComponentUpdate, in which it compares the current props and state with the next ones and returns false if the equalities pass.

See

atom/src/lines-component.coffee

Lines 74 to 92 in 97a671c

	shouldComponentUpdate: (newProps) ->
	return true unless isEqualForProperties(newProps, @props,
	'renderedRowRange', 'lineDecorations', 'highlightDecorations', 'lineHeightInPixels', 'defaultCharWidth',
	'overlayDecorations', 'scrollTop', 'scrollLeft', 'showIndentGuide', 'scrollingVertically', 'visible',
	'scrollViewHeight', 'mouseWheelScreenRow', 'scopedCharacterWidthsChangeCount', 'lineWidth', 'useHardwareAcceleration',
	'placeholderText', 'performedInitialMeasurement', 'backgroundColor', 'cursorPixelRects'
	)
	{renderedRowRange, pendingChanges} = newProps
	return false unless renderedRowRange?
	[renderedStartRow, renderedEndRow] = renderedRowRange
	for change in pendingChanges
	if change.screenDelta is 0
	return true unless change.end < renderedStartRow or renderedEndRow <= change.start
	else
	return true unless renderedEndRow <= change.start
	false

[mcharytoniuk]

I know that maybe it's too late for such ideas but I'd try moving away at least cursor component out of lines component and position it absolutely on top of it to prevent lines component updates caused by cursor movement. Also, Flipboard published react-canvas recently. Did you ever consider using canvas for animations / some editor elements as they did? Many people criticised them for negative SEO impact but inside text editor every crazy trick is acceptable imo. :)

[nathansobo]

A big selling-point of Atom is the ability to style content with CSS. Used properly, the DOM doesn't introduce prohibitive overhead for our use case.

React being removed is purely an implementation detail in this case and shouldn't affect package authors in any way. Appreciate your concern and suggestions here, but on balance it's easier to achieve our goals without it in this case.