Placeholder Rows

[pottedmeat]

Enhancement

When interacting with the grid, we will often see a row that spans all columns that contains a simple message about the behavior taking place. In dgrid 1, the following overrides appear (as strings):

• loadingMessage
• noDataMessage
• errorMessage

As an attempt to cover all situations placeholder rows may appear, consider the following:

• Loading message: when a row has been scrolled to but the data for that row has not yet been loaded, in the case of very large data sets
• Loading message: when expanding a tree, a single row may be added showing data is being loaded with information about what is being loaded or multiple loading rows showing the data for that row has not yet been loaded
• Error: when an asynchronous operation fails, it could add an interactive row to trigger a retry, or outline a catastrophic error in the case of being offline
• No data: when filtering/searching results in no data being found

The discussion we should have is whether we can outline every situation we expect to encounter during grid interaction and provide widgets for these, exposed through the grid's registry or introduce a completely dynamic approach where we ask a callback for the widget to use based on an item the data provider placed in the data set.

[dylans]

Presumably the placeholder rows will just be widgets, and they can existing as something that covers an entire dgrid, the entire body of the grid (excluding headers/footers), a row, or a cell (or any other widget level in a grid). Beyond that they contain a series of messages, some standard, and perhaps some that are custom). I can conceive a scenario where dismissing them could trigger a change event. For example, suppose the data was empty because of a network timeout or the data becomes stale (the latter of which is perhaps another message to have for a placeholder?), and the user wants to refresh/try again?

cc @matt-gadd and @agubler for their thoughts.