Feature request: add support for Handsontables mergeCells option to TableBlock

I set 'mergeCells': True and added 'mergeCells' to contextMenu list in table_options of a wagtail’s TableBlock.

I get functionality of merging cells in context menu of a table in an admin interface while editing a TableBlock widget. It works as expected merging and unmerging cells with content in it.

But all merged cell states got lost when I save a page. It seems that table structure and content converts to list disregarding information of merged cells before sending to a server. You can see this table structure in the browser’s request.

It was never worked before, but Handsontable was upgraded in latest Wagtail version, so I checked it on a latest version (2.6.1), but no luck.

Technical details

Django 2.2 Wagtail 2.6.1 Python 3.6

[dianelac]

Hello guys!. Please can we have an update to know if this issue will be fixed any time soon?

[jandor64]

I dug into this a bit, the .getData() call on Handsontable only returns the data in each cell, if it is merged it will return null. That’s not useful, since an empty cell will return null as well.

https://github.com/wagtail/wagtail/blob/c76447246dda344067af502c44388470a0513a91/wagtail/contrib/table_block/static/table_block/js/table.js#L92-L98

I think a new piece of data would need to be added to track the output of hot.getPlugin('mergeCells').mergedCellsCollection.mergedCells

Which will give us something like { col: 1, colspan: 3, removed: false, row: 1, rowspan: 3 }

That, in turn, gets stringified and stored, and then needs to be used when re-initializing this table in the admin, and needs to be worked into the logic for outputting the table template.

I have a JSFiddle demo of retrieving that data on a basic table. https://jsfiddle.net/cx35v1e0/

I don’t know enough about Wagtail to know where to start or how to contribute right now but happy to help if I can.