Sergey Linev

I not yet test latest `nlohmann/json.hpp`, but seems to be it is incompatible with previous versions. The simple solution for now would be ignoring incompatible versions of `nlohmann/json.hpp` and use...

> I assigned this issue to @Axel-Naumann, because probably he remembers best why the manual forward declaration was introduced. Optimally, we'll find a solution where the official json_fwd header can...

llvm13 branch works with plain `nlohmann/json.hpp`. Once it is merged, one can easily resolve this issue

Original issue related to the fact, that each new version of `nlohmann/json.hpp` requires own forward declaration like it used in REveElement.hxx: https://github.com/root-project/root/blob/master/graf3d/eve7/inc/ROOT/REveElement.hxx#L24-L37 Without llvm13 one cannot directly include `nlohmann/json.hpp` in...

This should be tested - I compile llvm13 branch, replace forward declaration in eve7 and add TJSONFile with nlohmann/json in header. It works, but makes lot of warnings. Why one...

> Indeed, placing #include into one of the existing io/ headers seems to work Not really. One can generate dictionary and compile code. But if one tries to load such...

Another "simple" approach to compile ROOT is specify `-Droot7=OFF`. This will disable eve7 compilation which has such problem with forward declarations.

@veprbl Can you check that https://github.com/root-project/root/pull/10999 fixes the problem?

Yes, I see same problem in JSROOT. It is because we are using different coordinates inside frame for axes/grids/histogram drawings and for `TLine` which is drawn in the pad coordinates....

In the ROOT it is pure rounding problem which will be fixed by #14837 In JSROOT it is SVG frame layer with integer coordinates and therefore rounding works differently. Solved...