How is Tableau built?

A really basic question about how desktop software is built.

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Software developers: if you were to re-build a data visualization tool like Tableau, how would you do it (at a high level)? What design/structure choices would you be making upfront?

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Context: Software dev is still kinda a mystery to me. I've built some web apps and do a good bit of data visualization and scripting, but that's another world. I hear vague things like "oh you'd just build it in C++", but I don't really know what that means: are there packages that represent things like window elements as objects? What would the codebase for a desktop-based data visualization application actually look like?