fix(eraser): solves issues with eraser

[NLueg]

Hi there!

I struggled a lot with implementing an undo and erase feature for my canvas.
After research, I found issue #421 which already provides a well-working version.

This PR includes the suggested changes which are provided by @JoeLeung32 (btw. thank you so much!)

[UziTech]

This library is meant to be for signatures so an erase feature doesn't really make sense. If you want to create a drawing_pad library that does this that would make more sense but I don't think an erase feature will be added to this library.

[NLueg]

I know, that it's not the main focus of this plugin. But actually, you have a Stackblitz link for the Erase feature at the top of the README.
Currently, this feature doesn't work although you advertise it there. We can close this PR if this is not intended but maybe you should make this clear in the README and remove the Stackblitz link.

After struggling a lot I just found the issue I mentioned and the fix from more than 4 years ago worked pretty well.

[UziTech]

@szimek what do you think about this feature? We would just need to add compositeOperation to pointGroupOptions, or we could abstract it with something like isErase?

[NLueg]

@UziTech thanks for the fast review! Actually, I don't thought about the changes proposed in the issue. I refactored the code as you requested and verified it in my fork.
It still works perfectly as expected and is much less hacky. Thank you!

[UziTech]

Thanks for simplifying it! Can you write a new test with erase and fix current tests?

[NLueg]

Thanks for simplifying it! Can you write a new test with erase and fix current tests?

I added a test that checks whether the set compositeOperation is applied to the canvas context. Do you think that is enough? Or what test do you want to have?

[UziTech]

LGTM

[github-actions]

🎉 This PR is included in version 4.1.6 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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[yserlong]

Hello,
since this change my project won't build anymore. It throw an error telling it can't find the type : GlobalCompositeOperation.
Maybe it's a compatibility problem with the typescript version or something ?

[UziTech]

Looks like this may require Typescript 4.6 or higher