René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Better update pattern for cartesian SVG","articleBody":"As @etpinard pointed out during the finance refactor PR https://github.com/plotly/plotly.js/pull/2561#discussion_r181852562 and https://github.com/plotly/plotly.js/pull/2561#discussion_r181856275 we have a mess when redrawing cartesian SVG traces, both re: deleting and redrawing existing traces and re: removing completely unused modules.\r\n\r\nThe first part we can handle by making all the trace modules support more d3-idiomatic `enter/exit/each` logic as suggested in [this TODO](https://github.com/plotly/plotly.js/blob/82677ac8745ca56da740302977533dffcd5521b6/src/plots/cartesian/index.js#L201). The second has a few ways to go about it. Quoting @etpinard:\r\n\r\n\u003e What we need to do is find all the _gone_ modules (i.e. modules with `had??=true` and `has??=false`), loop over them, and then do what we need to do the cleanup the DOM. \r\n\u003e \r\n\u003e Better yet -- as more and more trace type will follow scatter and ohlc in not expecting a `selectAll('g.trace').remove()` before each `_module.plot()` -- we could add a trace module method (maybe called `cleanDOM`) to each trace modules that need to remove things for the DOM (or destroy WebGL objects). \r\n\u003e \r\n\u003e To note, geo subplots (and maybe others?) solve this problem in a different way by using `Plots.generalUpdatePerTraceModule` which calls `_module.plot` of visible **and**  _gone_ modules and expects the trace module plot methods to clean up the DOM accordingly (e.g. like [here](https://github.com/plotly/plotly.js/blob/18e19a86a3e683c1d11f6f4a04eb7f89d1b6108f/src/traces/choropleth/plot.js#L34) for choropleth traces). At present though, I think adding `cleanDOM` to each trace module would be best, as it would allow us to handle the `scattergl` and range-slider cases more easily.","author":{"url":"https://github.com/alexcjohnson","@type":"Person","name":"alexcjohnson"},"datePublished":"2018-04-16T22:41:18.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/2563/plotly.js/issues/2563"}