What do UX guidelines say about dropdown boxes in table cells?

Question

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I have been trying to look at Apple Interface Guidelines and Windows UX guidelines about what standard behavior for drop down menus in table cells should be. I can't find any mention of it. My specific questions are:

1. Should the drop down always be visible or only appear when user clicks in a cell to edit it?
2. Should it drop down on single click or on double click?

In e.g. Qt GUI toolkit the standard behavior is that cells with comboboxes look like regular text fields. When you click them to edit, you see the combobox and can click it. This means you always have to have a double click. In other applications I have seen that you always see the combobox and you only need a single click.

Perhaps there is no standard, but then what are the tradeoffs? When should you use one approach over another.

Edit: this is for a desktop application, so I'm not interested in best practices for webpages. I see a lot of the comments are related to web UIs.

Answer 1

Think hard about what the grid is primarily used for. To answer #1 (should the drop down always be visible): Is this a grid where the user is expecting to edit the information ~80% of the time? If so, perhaps it's more usable to have the drop down always be visible. There's a fine line between a clean UI and an unusable one, and the most usable and functional interfaces aren't always ones that win awards for being the prettiest. If ~80% of the time, users will be referencing the table for data and are not likely to be changing, that may be an indication of not showing the drop downs until needed.

Keep in mind that opting to show drop downs all of the time may present scalability issues: how many rows will your grid have, and how many columns will have drop downs in them, and how many options will each drop down have in it? For large data sets, it may not feasible to present drop downs in a grid this way.

For #2: I'd err on the side of one-click. If a user is clicking in to a field with the purpose of editing it, then having to click again to expand the drop down box seems superfluous.

While Telerik doesn't have an example of editing a row with a drop down column, I do like their demos of options for editing rows of data: http://demos.telerik.com/aspnet-mvc/grid/editingbatch?theme=vista which may help you brainstorm different options.

Answer 2

I think about google docs and the spreadsheet. I think there's the baseline. I think in a table the dropdown should only be a function of selection or in an "edit" state. While this is a double tap or click, there's enough precedent out there for inline editing to be activated this way. Honestly, I'm not sure why you couldn't just have predictive text populate as the user types and have new values/input populate the list along the way, similar to the way a user can add tags in Evernote.

All that said, I agree with the other comment...does it need the grid in the first place?