Screwy use of Labeled in BarChart -- possible bug

Question

SetOptions[BarChart, LabelStyle -> {}];
Options[BarChart, LabelStyle]

When I evaluate this code

BarChart[Labeled[#, Rotate["label", 90 Degree], Above, 
    LabelStyle -> Directive[Red, FontSize -> 32]] & /@ Range[8]]

with V11.0.1 on OS X I get

When I examine the InputForm the labels are coded like this:

Text[Style[
  Rotate["label", 
   90*Degree], {LabelStyle -> 
    Directive[RGBColor[1, 0, 0], FontSize -> 32], Directive[], 
   Directive[]}], Offset[{0, 4}, {1., 1.}], ImageScaled[{0.5, 0}]]

So we have the LabelStyle for Labeled plus duplicates of the global LabelStyle for BarChart.

SetOptions[BarChart, 
  LabelStyle -> Directive[RGBColor[1, 0, 0], FontSize -> 12]];

Now I get:

with the labels configured this way:

Text[Style[
  Rotate["label", 
   90*Degree], {BaseStyle -> 
    Directive[RGBColor[1, 0, 0], FontSize -> 24], 
          LabelStyle -> Directive[RGBColor[1, 0, 0], FontSize -> 32], 
   Directive[RGBColor[1, 0, 0], FontSize -> 12], 
          Directive[RGBColor[1, 0, 0], FontSize -> 12]}], 
 Offset[{0, 4}, {1., 1.}], ImageScaled[{0.5, 0}]]

which confirms the duplicate of the BarChart LabelStyle Directive. The configuration of the styling options for these labels looks to be a mess. I'm assuming that being unable to locally style the label use the Labeled LabelStyle option is a bug?

And when I try this:

SetOptions[BarChart, LabelStyle -> {}];
BarChart[Labeled[
    Style[#, Directive[FontColor -> Red, FontSize -> 32]], 
    Rotate["label", 90 Degree], Above] & /@ Range[8]]

I get this:

 Text[Style[Rotate["label", 90*Degree], {Directive[], Directive[]}], Offset[{0, 4}, {5., 5.}], ImageScaled[{0.5, 0}]]

Note also that modifying the LabeledLabel style in my stylesheet also had no effect.

This appears to be either a bug or a design oversight. Does anyone have any thoughts?

Answer 1

This looks like a bug. I'll seek confirmation from WRI and post accordingly. In the meantime Carl's suggestion is a work around:

BarChart[Labeled[#, Rotate["label", 90 Degree], Above, Directive[Red, FontSize 
-> 32]] & /@ Range[8]]

or alternatively from @kglr:

BarChart[Labeled[#, Style[Rotate["label", 90 Degree], Red, 32], Above] & /@ Range[8]]

Answer 2

It appears there is a missing step in the processing of LabelStyle within the Labeled wrapper, if it is to work as desired. I think Carl Woll's work-around does this manually but it should be done automatically.

Most of the options of Labeled apply not to the labels themselves but either to be object being labeled, e.g. Background and Frame, or affect the overall layout e.g. Spacings and ImageSize. I think it makes sense for these options to be ignored by BarChart as it has its own directives for these aspects.

Attempting to dig through the Charting` definitions it is hard to know where exactly handling of LabelStyle should have been applied.

We can get some possibly useful information by turning on Charting debug printing:

Charting`dbPrint = Print;

Now:

SetOptions[BarChart, LabelStyle -> {}];

BarChart[
  Labeled[#, "label", Above, 
     LabelStyle -> Directive[Red, FontSize -> 32]] & /@ Range[8]
]

iBarChart via: BarChart

ChartParser: hasWrappedInputQ: True

ChartParser: WrapperFunctions: {{1}->{{Labeled,label,Above,LabelStyle->Directive[,FontSize->32]}},{2}->{{Labeled,label,Above,LabelStyle->Directive[,FontSize->32]}},{3}->{{Labeled,label,Above,LabelStyle->Directive[,FontSize->32]}},{4}->{{Labeled,label,Above,LabelStyle->Directive[,FontSize->32]}},{5}->{{Labeled,label,Above,LabelStyle->Directive[,FontSize->32]}},{6}->{{Labeled,label,Above,LabelStyle->Directive[,FontSize->32]}},{7}->{{Labeled,label,Above,LabelStyle->Directive[,FontSize->32]}},{8}->{{Labeled,label,Above,LabelStyle->Directive[,FontSize->32]}}}

.

.

.

Wrappers defined in Charting`ParserDump`$ApplicationWrapperFunctions which include Labeled appear to be handled generically.

Charting`ChartParser is used to process the chart data. It calls Charting`ParserDump`processWrappers which contains the definition:

(* contexts stripped for brevity *)

processWrappers[obj_, d : h_[x_, y___], pos_, wrappers_List] /; 
  MemberQ[wrappers, h] :=
 Module[{data},
  appendProperty[obj, 
   "WrapperFunctions", {pos -> 
     Which[MemberQ[$SystemWrapperFunctions, h], data = x; {h, h[#1, y] &}, 
      MemberQ[$ApplicationWrapperFunctions, h], data = x; {h, y}, 
      MemberQ[$MetaWrapperFunctions, h], data = x; {h, y}, 
      MemberQ[$ModelWrapperFunctions, h], data = d["InputData"]; {h, d}, True, 
      dbPrint["processWrappers: ", h, " is not in any of the wrapper lists. "]]}]; 
   processWrappers[obj, data, pos, wrappers]
 ]

Note that for every Application Wrapper Function the same transformation is applied, i.e. wrapper[foo, bar, baz] -> {wrapper, bar, baz}.

I get lost in the definitions here but I cannot find anything that would handle LableStyle specifically.