classNameDefinedColumns() now identifies negative and "_all" targets

[shrektan]

closes #511

The fix #476 misses the fact that besides of column indexes, there're 4 kinds of columnDefs.targets in total.

• 0 or a positive integer - column index counting from the left
• A negative integer - column index counting from the right
• A string - class name will be matched on the TH for the column (without a leading .) See the comment below.
• The string "_all" - all columns (i.e. assign a default)

This PR is meant to handle all the rest cases. However, for case 3, I can't reproduce the effect in the first place. What I mean is explained by the following example:

UPDATE 20180425 This is because DT sends out the data as an array instead of an object. So the datatables library itself doesn't know the column names of each column.

DT::datatable(
  data.frame(a = 1, b = 2, c = 3, d = 4),
  options = list(
    columnDefs = list(
      list(className = "dt-center", targets = "a") 
      # it should have set "a" column center alignment, but it didn't
    )
  )
)

For 1, 2 and 4 cases, they are correctly handled now.

DT::datatable(
  data.frame(a = 1, b = 2, c = 3, d = 4),
  options = list(
    columnDefs = list(
      list(className = "dt-center", targets = "_all")
    )
  )
)

DT::datatable(
  data.frame(a = 1, b = 2, c = 3, d = 4),
  options = list(
    columnDefs = list(
      list(className = "dt-center", targets = c(-1, 2))
    )
  )
)

[yihui]

Thanks!

[yihui]

Can you also add an item in NEWS.md?

[shrektan]

My bad, added.

For the case 3 A string - class name will be matched on the TH for the column (without a leading .), any ideas why it won't work?

[yihui]

I have no idea. As long as #511 is fixed, I don't really care much for now. Thanks!

[vnijs]

FYI Although the examples @shrektan created for these cases seem to work, I can still recreate issue if the first column is an integer using version 0.4.2 from GitHub (see screenshot and example below).

DT::datatable(
  sapply(iris[,1:3], as.integer),
  options = list(
    columnDefs = list(
      list(className = "dt-center", targets = "_all")
    )
  )
)

In the above example, the issue goes away if the data is in a data.frame rather than a matrix, but I can also reproduce the issue in a shiny app where the input is a data.frame (see screenshot below)

[shrektan]

@vnijs My bad. It must be something related to the row names... Will file a patch now... Apologize for the trouble.

[vnijs]

No trouble all @shrektan. I'm grateful for your time and effort

[shrektan]

@vnijs Thanks. I've submitted the PR #514 to fix this. Let me know if still problems.