d3/d3-brush

brush.on("end", handle) seems to get raw "mouseup" events

gnarf opened this issue · 7 comments

gnarf commented

http://jsbin.com/rofenucicu/2/edit?js,console,output

I was expecting this to return an "end" event with a event.selection

mbostock commented

This is appears to be an issue with the use of destructuring assignment rather than import:

const {brush, event, select} = d3;

The problem here is that d3.event is not a constant: it changes whenever there’s an event.

If you save the value of d3.event on load, you should expect it to always be undefined. However, it’s not here because some browsers emulate IE’s global window.event, overriding your const event, and hence you are seeing the native input events rather than the brush events.

If you change your code to refer to d3.event instead of event (and remove the const event) it works fine. If you use vanilla JavaScript, it also works fine:

http://bl.ocks.org/mbostock/15a9eecf0b29db92f12ca823cfbbce0a

You should also be able to import {event} from "d3" if you use ES6 modules. But that gets tricky because you need to make sure that "d3" in that case refers to D3’s ES6 modules, and not the UMD bundle, so that the import is properly resolved.

gnarf commented

Okay, tested with d3.event in my fiddle...

I am doing import {event} from "d3"; but still having this problem in my production code.

mbostock commented

Right. The import {event} from "d3" is probably an issue with Babel not respecting that imports are live bindings, not values. But I’m not sure whether that problem is caused by Babel trying to import from the D3 UMD bundle or whether it’s observing the jsnext:main field in the package.json like Rollup does and pulling directly from the ES modules.

gnarf commented

So yeah -- I got this working now...

Had to in my webpack force it to resolve "d3" to d3/index.js instead of the d3/build/d3.js, and ensure babel was parsing the node_modules/d3 directories

However this is a very annoying problem that I'm sure will catch a lot of users... Perhaps you should build a safer export for event. Even something as silly as import {d3event} from 'd3'; d3event.event might be a safe alias for UMD users that wont have binding/destructuring problems like I just did...

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mbostock commented

Does webpack not observe jsnext:main? Is there some other magic I can put in the package.json to tell it to find index.js instead of build/d3.js?

mbostock commented

I’ve added some text to the README that will hopefully help avoid this issue:

If you use Babel, Webpack, or another ES6-to-ES5 bundler, be aware that the value of d3.event changes during an event! An import of d3.event must be a live binding, so you may need to configure the bundler to import from D3’s ES6 modules rather than from the generated UMD bundle; not all bundlers observe jsnext:main. Also beware of conflicts with the window.event global.

https://github.com/d3/d3-selection/blob/master/README.md#event

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