Add notes for July, 7

2016-07/july-07.md

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+## July 07 ([discuss](https://github.com/reactjs/core-notes/pull/23))
+
+### Attendees
+
+* [Ben](https://twitter.com/soprano) (React)
+* [Dan](https://twitter.com/dan_abramov) (React)
+* [Keyan](https://twitter.com/keyanzhang) (React, intern)
+* [Paul](https://twitter.com/zpao) (React)
+* [Sebastian](https://twitter.com/sebmarkbage) (React)
+* [Tom](https://twitter.com/tomocchino) (React)
+
+### Fragments
+
+* We don’t currently allow returning multiple elements from `render()` method.
+* This has been a [long requested feature](https://github.com/facebook/react/issues/2127) in the community.
+* We generally agree that it should be implemented but we found it to be hard with our existing architecture.
+
+#### Existing Solutions
+
+* There exists a [fork](https://github.com/facebook/react/issues/2127#issuecomment-216401555) that implements fragments but we don’t want to take this implementation.
+* It introduces them only for React DOM which would make React features inconsistent across renderers.
+* It also introduces some complexity we would like to avoid because we might start breaking other things with it.
+
+#### Our Plans
+
+* [Fiber](https://github.com/reactjs/core-notes/blob/master/2016-06/june-23.md#update-on-fiber) supports fragments but it’s far from done.
+* We will include work on fragments in our plan for the second half of 2016.
+* Since we want this feature anyway, we can implement it in existing reconciler independently of Fiber.
+
+### Build Size
+
+* We think that React provides good value for its build size (~45kB min+gzip).
+* However we understand everybody has different constraints, especially with small apps.
+* We intend to be [more mindful](https://github.com/facebook/react/issues/7205) of the build size to avoid accidental regressions.
+
+#### Rollup
+
+* [Keyan](https://twitter.com/keyanzhang) is investigating using [Rollup](http://rollupjs.org/) for our UMD builds. ([#7178](https://github.com/facebook/react/pull/7178))
+* After [#7178](https://github.com/facebook/react/pull/7178) is merged, the minified post-gzip size will reduce by 14%. (46kB → 39kB)
+* For now, we will use [a hack](https://github.com/facebook/react/pull/7178#issuecomment-230379738) to transpile CommonJS to ES Modules so Rollup understands them.
+* Longer term, we’d like to use ES Modules in the source but Facebook internal bundlers don’t understand them yet.
+
+#### Event System
+
+* [Dan](https://twitter.com/dan_abramov) asked why the event system is so large.
+* It accounts for a noticeable chunk of React build size.
+* Looking at other “React-like” libraries, no one has an event system like ours. Why?
+
+##### Why We Need It
+
+* The intention was to normalize events with weird behavior like `mouseenter` or `focus` across browsers.
+* This lets component authors not worry about inconsistencies with bubbling and input events, making ecosystem better.
+* The React Native gesture handling system is also built around it.
+* The browsers have improved, so we will keep re-evaluating it once in a while, but for now we find it useful.
+
+##### What We Can Improve
+
+* It is overabstracted, and we can simplify code by baking support for some [“plugins”](https://github.com/facebook/react/tree/1a0e3a32150468223d6f9fd0125db0f8503b76d6/src/renderers/dom/client/eventPlugins) right into it.
+* There is some code duplication we can reduce in [the event whitelist](https://github.com/facebook/react/blob/1a0e3a32150468223d6f9fd0125db0f8503b76d6/src/renderers/dom/client/eventPlugins/SimpleEventPlugin.js).
+* Some weird patterns like [`keyOf()`](https://github.com/facebook/react/blob/1a0e3a32150468223d6f9fd0125db0f8503b76d6/src/renderers/dom/client/eventPlugins/SimpleEventPlugin.js#L40-L41) exist to be compatible with [GCC](https://www.google.co.uk/search?q=google+closure+compiler&gws_rd=cr&ei=O7x-V_66AonOgAbov6GACA). Perhaps we could find another way to fix this?
+
+------------
+
+Please feel free to discuss these notes in the [corresponding pull request](https://github.com/reactjs/core-notes/pull/23).