PlotMarkers doesn't inherit PlotStyle when first argument to Graphics isn't a list

Question

Bug fixed in 12.0

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Could somebody explain, why Circle does not inherit the PlotStyle of the plot when used as PlotMarkers? Here is an example:

l1 = RandomInteger[100, {20, 2}]
cross = Graphics[{Line[{{-1, 1}, {1, -1}}], Line[{{1, 1}, {-1, -1}}]}];
circle = Graphics[Circle[{0, 0}, 1]];
ListPlot[l1, PlotStyle -> Thick, PlotMarkers -> {cross, .03}]
ListPlot[l1, PlotStyle -> Thick, PlotMarkers -> {circle, .03}]

This seem to work as expected, but the only difference is that Graphics is given a list of primitives:

circle1 = Graphics[{Circle[{0, 0}, 1]}];
ListPlot[l1, PlotStyle -> Thick, PlotMarkers -> {circle1, .03}]

Answer 1

After reading the documentation for PlotStyle and Graphics I have the following hyopthesis:

PlotStyle tries to apply a graphics directive to the object circle, but as it is written in your example, circle is syntactically incorrect for accepting the directive. The syntax for applying a graphics directive to a graphics primitive must be of the form:

Graphics[{*directive1*,*directive2*, ..., *primative*[*co-ords,etc*]}]

I.e. The {} may need to be in place to allow PlotStyle to impart the directive to the object.

E.g. if circle is defined as

circle = Graphics[{Opacity[.1], Circle[{0, 0}, 1]}];

The resulting PlotMarkers will have Thick outlines and Opacity[.1]

This is consistent with composite primitives and single primitives (e.g. your cross and circle, respectively) being treated in the same fashion by Plot. In which case it is not a bug, just strict syntax.