feat(core): add optional Top-Header for Drag Grouping & Header Grouping

[ghiscoding]

• prior to this PR, we could not use Draggable Grouping & Header Grouping because both features were using the pre-header and it would have conflict, now to avoid this I am adding an extra Top-Header that will show over all header and pre-header.
• NOTE: Draggable Grouping can now be displayed in either the new Top-Header OR the Pre-Header. However, the users who do want to use both features will need to explicitely enable both top/pre headers.
• I was getting a little out of ideas to get a name (since "pre" is already taken), so I decided to go with Top-Header which is completely on the top and even before the pre-header.
• Another note is that this new Top-Header is not following the frozen columns (like header & pre-header do) and is rather always the same width as the grid. I purposely did not want this top-header to follow the grid frozen columns because I wanted a simpler header and also because I expect this to be mostly (and only) be used by the Draggable Grouping.

TODOs

• [x] need more unit tests
• [x] need more Cypress E2E tests (Example 3)
• [x] Example 18 is now broken (not currently able to show Draggable Grouping without Header Grouping)
• [x] throws an error when following these 2 steps (1. drag a column to group, 2. freeze a column)
  • it should be fixed in separate PR since it's an existing bug (reproducable in previous version)
  • also throws when calling unfreeze all columns
  • fixed in PR #1557
• [x] see if we need docs update

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[ghiscoding]

cc @zewa666 so I came up with a new Top-Header (as explained above), if you have a better name then please let me know. This new Top-Header is created on top of all the headers hence his name. Prior to this PR, the example above was not possible. Header Grouping (those are grouped header titles, e.g. "Period") will always use and require the pre-header to exist.

| Top Header | | Pre-Header | | Headers |

Side note, how is it going with your PRs? I'm probably going to target a release by next weekend, so if you need more time then we could release future patches. I would prefer to include everything in 1 go, but there's really no pressure at all, I'm just planning ahead :)

[zewa666]

Aggrid calls them simply columngroups but I dunno if this fits this usecase. I do wonder though if grouping is supported for backendservices.

my PRs are somewhat stuck atm as I'm getting my app ready for stage and prod these days. So I guess I'll get back to it next week along with the first user feedback.

so far really the only feedback of a missing feature was the individual row heights along with cell content wrapping but I managed to dodge that bullet with customTooltips 😅

[ghiscoding]

Aggrid calls them simply columngroups but I dunno if this fits this usecase. I do wonder though if grouping is supported for backendservices.

Header Grouping works as shown in Example 10, but Column Grouping is not supported for backend (well it's just partially supported and not what users are expecting since the way I've got Backend Services working is to always flush the DataView data every time you change page, and since Grouping is built by the DataView then you can only support Grouping for the data you currently have which is equal to Grouping 1 page and is not what users want). I had to write to over and over because many users want this feature but it's just too much work and I don't want to spend time on supporting this (I actually wouldn't even know where to start with this since like I said it's the DataView that supports Grouping with current data and we surely don't want to load the entire dataset because that goes against the Backend Service philosophy).

so far really the only feedback of a missing feature was the individual row heights along with cell content wrapping but I managed to dodge that bullet with customTooltips 😅

yup that's also another subject that was discussed so many times and is not quite possible since SlickGrid uses div and virtual scroll. It's actually doable with a lot of work to support dynamic row height, it was explained by Violet in this SO and I actually took some of that concept to create the Row Detail plugin (you can see her article Wooohoo! a responsive SlickGrid with dynamic row-heights, there's a link on the top of the article that you can click to see all her steps, there's a lot). Note that even if she's somehow showing dynamic row height, it has to follow a row height multiple which is what I followed in Row Detail (i.e. you tell the plugin how many rows you want to use)

So I guess I'll push a new release by the end of this week and you can go back to your PRs whenever you have time. I want to clear up all the PRs I enqueued in each repos (7x in each). So I need to finish this PR and I guess that I'll stick with Top-Header name (I think it's fine, I certainly don't want to use "prepreheader" lol). I also have to look into a small bug that someone just opened this morning on Angular-Slickgrid Tree Data

[zewa666]

sure go ahead dont need to wait for me. I'd like to make sure to test out those changes properly and than finish the PRs missing parts like docs and tests