- Remove the dependency on fit-curve;
- Improve the way to draw the current line in using a Path2D and
in clearing only the last part of the curve instead of clearing
all the canvas;
- Smooth the curve when drawing to avoid to have some changes after
the drawing ends;
- Make the smoothing a bit less agressive.
The previous version was maybe functional but definitely painful to maintain
(maybe more efficient... I don't know) so this patch aims to simplify it and
it adds some basic unit tests.
Rather than including all of this external code in the PDF.js repository, we should be using the npm package instead.
Unfortunately this is slightly more complicated than you'd hope, since the `fit-curve` package (which is older) isn't directly compatible with modern JavaScript modules.
In particular, the following cases needed to be considered:
- For the development viewer (i.e. `gulp server`) and the unit-tests, we thus need to build a fitCurve-bundle that can be directly `import`ed.
- For the actual PDF.js build-targets, we can slightly reduce the sizes by depending on the "raw" `fit-curve` source-code.
- For the Node.js unit-tests, the `fit-curve` package can be used as-is.
