Fix the issue that the maximum width of the column does not change when a format is applied to the column (#86)

* Improve the speed of displaying large datasets in Jupyter Notebook

Fix the issue that Jupyter Notebook takes too much time when displaying large datasets with many columns.

The getmaxwidths() function now only calculates the maximum width of the columns that will be displayed, not all columns.

Please see issue for more details.

* Modify the initialization code of maxwidths

Now might break the loop before filling all the values of maxwidths.

The initialize code of maxwidths has been modified.

* Fix the issue that the maximum width of the column does not change when a format is applied to the column

When the getmaxwidth() function calculates the maximum width of a column, the format is not applied to the column. When the user sets the format, the maximum number of columns that the Dataset can display is still calculated according to the original data. However, the maximum number of displayed columns may change after setting the format.

Now the format of each column will be applied before calculating the maximum width of the column. The maximum number of columns that can be displayed will be changed correctly.

* Add mapformats keyword argument to getmaxwidths() and _show()

The FOR loop is duplicated so that mapformats only need to be determined once.

* Update io.jl

Simplify part of the code of getmaxwidths()

* Update io.jl

Make mapformats as a keyword argument and update the docstring of the getmaxwidths() function.

Author: Kexi002

src/abstractdataset/io.jl

@@ -6,13 +6,15 @@
                             rowlabel::Symbol,
                             rowid::Union{Integer, Nothing},
                             show_eltype::Bool,
-                            buffer::IOBuffer)
+                            buffer::IOBuffer,
+                            truncstring::Int;
+                            mapformats::Bool = true)
 
 Calculate, for each column of an AbstractDataset, the maximum
 string width used to render the name of that column, its type, and the
 longest entry in that column -- among the rows of the data frame
-will be rendered to IO. The widths for all columns are returned as a
-vector.
+will be rendered to IO. The widths for the columns that will be displayed 
+are returned as a vector.
 
 Return a `Vector{Int}` giving the maximum string widths required to render
 each column, including that column's name and type.
@@ -35,6 +37,10 @@ implicit row ID column contained in every `AbstractDataset`.
 - `show_eltype`: Whether to print the column type
    under the column name in the heading.
 - `buffer`: buffer passed around to avoid reallocations in `ourstrwidth`
+- `truncstring`: The length of the string to be truncated. The string will
+   not be truncated if it is equal to 0.
+- `mapformats`: Whether to calculate the max widths after mapping format 
+   for each column.
 """
 function getmaxwidths(ds::AbstractDataset,
                       io::IO,
@@ -44,7 +50,9 @@ function getmaxwidths(ds::AbstractDataset,
                       rowid::Union{Integer, Nothing},
                       show_eltype::Bool,
                       buffer::IOBuffer,
-                      truncstring::Int)
+                      truncstring::Int;
+                      mapformats::Bool = true)
+
     maxwidths = zeros(Int, size(ds, 2) + 1)
 
     undefstrwidth = ourstrwidth(io, "#undef", buffer, truncstring)
@@ -57,7 +65,11 @@ function getmaxwidths(ds::AbstractDataset,
         # (1) Consider length of column name
         # do not truncate column name
         maxwidth = ourstrwidth(io, name, buffer, 0)
-
+        # Calculates max widths after mapping formats if mapformats = true, because formats may affact the max widths
+        if mapformats
+            f = getformat(ds, col_idx)
+            col = f.(col)
+        end
         # (2) Consider length of longest entry in that column
         for indices in (rowindices1, rowindices2), i in indices
             if isassigned(col, i)
@@ -133,10 +145,10 @@ julia> show(stdout, MIME("text/csv"), Dataset(A = 1:3, B = ["x", "y", "z"]))
 """
 Base.show(io::IO, mime::MIME, ds::AbstractDataset)
 Base.show(io::IO, mime::MIME"text/html", ds::AbstractDataset;
-          summary::Bool=true, eltypes::Bool=true) =
-    _show(io, mime, ds, summary=summary, eltypes=eltypes)
-Base.show(io::IO, mime::MIME"text/latex", ds::AbstractDataset; eltypes::Bool=true, mapformats = true, formats = true) =
-    _show(io, mime, ds, eltypes=eltypes, mapformats = mapformats, formats = formats)
+          summary::Bool = true, eltypes::Bool = true, mapformats = true) =
+    _show(io, mime, ds, summary = summary, eltypes = eltypes, mapformats = mapformats)
+Base.show(io::IO, mime::MIME"text/latex", ds::AbstractDataset; eltypes::Bool = true, mapformats = true, formats = true) =
+    _show(io, mime, ds, eltypes = eltypes, mapformats = mapformats, formats = formats)
 Base.show(io::IO, mime::MIME"text/csv", ds::AbstractDataset; mapformats = true) =
     printtable(io, ds, header = true, separator = ',', mapformats = mapformats)
 Base.show(io::IO, mime::MIME"text/tab-separated-values", ds::AbstractDataset; mapformats = true) =
@@ -171,7 +183,7 @@ function html_escape(cell::AbstractString)
 end
 
 function _show(io::IO, ::MIME"text/html", ds::AbstractDataset;
-               summary::Bool=true, eltypes::Bool=true, rowid::Union{Int, Nothing}=nothing)
+               summary::Bool=true, eltypes::Bool=true, rowid::Union{Int, Nothing}=nothing, mapformats = true)
     _check_consistency(ds)
 
     # we will pass around this buffer to avoid its reallocation in ourstrwidth
@@ -189,7 +201,7 @@ function _show(io::IO, ::MIME"text/html", ds::AbstractDataset;
     if get(io, :limit, false)
         tty_rows, tty_cols = displaysize(io)
         mxrow = min(mxrow, tty_rows)
-        maxwidths = getmaxwidths(ds, io, 1:mxrow, 0:-1, :X, nothing, true, buffer, 0) .+ 2
+        maxwidths = getmaxwidths(ds, io, 1:mxrow, 0:-1, :X, nothing, true, buffer, 0, mapformats = mapformats) .+ 2
         mxcol = min(mxcol, searchsortedfirst(cumsum(maxwidths), tty_cols))
     end