Alright I could give it a try! This might be a stupid question, can you tell me how to run the server from my fork? So that I can test the changes?

Thanks for opening the issue, @simonw. Let me elaborate on my Tweets.

datasette-chartjs provides drop down lists to pick the chart visualization (e.g. bar, line, doughnut, pie, ...) as well as the column used for the "x axis" (e.g. time).

A user can change the values on-demand. The chart will be redrawn w/o querying the database again.

However, if a user wants to change the underlying query, they will use the SQL field provided by datasette or any of the other datasette built-in features to amend a query. In order to maintain a user's selections for the plugin, datasette-chartjs copies some parts of datasette-vega which persist the chosen visualization and column in the hash part of a URL (the stuff behind the #). The plugin load the config from the hash upon initialization on the next page and use it accordingly.

Additionally, datasette-vega and datasette-chartjs need to make sure to include the hash in all links and forms that cause a reload of the page. This is, such that the config persists between clicks.

This ticket is about moving thes parts into datasette that provide the functionality to do so. This includes:

1. a way to load config options with a given prefix from the current URL hash
2. a way to update the current URL hash with a new config value or a bunch of config options
3. updating all necessary links and forms on the current page to include the URL hash whenever its updated
4. to prevent leaking config options to external pages, only "internal" links should be updated

There's another, optional, feature that we might want to think about during the design phase: the scope of the config. Links within a datasette instance have 1 of 3 scopes:

1. global, for the whole datasette project
2. database, for all tables in a database
3. table, only for a table within a database

When updating the links and forms as pointed out in 3. above, it might be worth considering which links need to be updated. I could imagine a plugin that wants to persist some setting across all tables within a database but another setting only within a table.

Codecov Report

Merging #1145 (a8588f9) into main (0c616f7) will not change coverage. The diff coverage is n/a.

```diff @@ Coverage Diff @@

main #1145 +/-

======================================= Coverage 91.41% 91.41%
======================================= Files 31 31
Lines 3881 3881
======================================= Hits 3548 3548
Misses 333 333
```

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I'm looking into using datasette with a database with spatialite geometry columns, and came across this issue. Has there been any progress on this since 2018?

In one of my tables I'm just storing lat/lon points in a spatialite point geometry, and I've managed to make datasette-cluster-map display the points by extracting the lat and lon in SQL - using something like select ... ST_X(location) as longitude, ST_Y(location) as latitude from Blah. Something more 'built-in' would be great though - particularly for the tables I have that store more complex geometries.