Computation of the precise bounding box with TikZ.
This library may be used and distributed under the LPPL License for LaTeX v1.3c. It can also be found on CTAN.
An earlier, proof-of-principle version of this library was added to pgf without me explicitly agreeing to this. (A pgf maintainer insists that, since I did not add a license, they had the right to add the library to pgf. This may well be the case, I am not an expert on this, all I am saying is that I was stressing that at that stage it was just a proof of principle and never agreed in any way that this library become a part of the public pgf package.) On the other hand, as opposed to the library that was part of pgf, this version of the library is streamlined and, in particular, fixes issues that were reported on the pgf GitHub site. While its manual was being typeset, some unrelated user started mocking the author on a public chat for using an ASCII editor. The result is that the maintainer of pgf removed the library from pgf. (They claim that I had changed the license. This claim is a lie.) Now the package has a separate entry on CTAN. While this is far from optimal since it is not possible to cross-reference statements in now two separate manuals, and one has to go to different GitHub sites to report issues, and "overlapping" issues that are caused by things that require changes in both pgf and this library cannot be really addressed. But at least it is on CTAN...
A side remark concerns other applications of this library, and the routines contained. It can conceivably be used to speed up the determination of intersections. Why? A path is a collection of cubic Bézier curves. (Straight lines and quadratic Bézier curves are special cases of cubic Bézier curves.) A segment in path A can intersect with a segment of path B if the intersections of the bounding boxes of the segments is nonempty.