Pascal seems a way too vintage programming language (not nearly as handy as C#, let alone C# 5.0) and the IDE's editor isn't nearly as intelligent as that of VisualStudio (let alone with ReSharper). But it indeed seems the only of the kind truly cross-platform. The only close-enough alternative I found on Linux was QtDesigner+Python but it still wasn't that convenient.
I adore people who code Lazarus (e.g. Double Commander authors - they have been doing an amazing job with visible progress and persistence all these years) though. Perhaps I'm going to dedicate some time to learn Pascal once, just for this. It would be easier if they had a seamlessly-compatible C++ version at least (like Delphi had).
Keep in mind that Free Pascal is not exactly the same as classic Pascal. The language has a lot of features you'd find in other modern (as much as Java and C# can be called modern nowadays anyway) object oriented languages. Things like classes, interfaces, dynamic message dispatch, properties with getters/setters, for with ranges, dynamic arrays, generics, a rich RTTI (though not as rich as managed languages - yet, it is work in progress - it is rich enough to do things like serialization, etc), etc.
As for a C++ version, it would be useful (though i find Free Pascal a better language overall, despite its warts - the only thing i wish it had from C++ was 'const' and slightly more powerful generics, but both aren't that big of an issue and generics are improving anyway) but VERY difficult to do as i wrote some time ago here [0] and here [1] where i went into more details about the language side of things (C++ Builder has extended C++ to allow for Object Pascal-isms because VCL itself is written, like LCL/FCL, in Pascal, which for Borland was possible because they made both the Pascal and the C++ compilers).
[1] https://news.ycombinator.com/item?id=19882489 (note that the discussion was originally about using LCL from C++ so i also mention the alternatives - and how not having the rest of the IDE would end up with a worse wxWidgets since LCL isn't really designed to be used purely via code)
I adore people who code Lazarus (e.g. Double Commander authors - they have been doing an amazing job with visible progress and persistence all these years) though. Perhaps I'm going to dedicate some time to learn Pascal once, just for this. It would be easier if they had a seamlessly-compatible C++ version at least (like Delphi had).