Add Bezier Shapes #1120

[xudesheng]

Closes #1120.

This is a replacement of the PR: #1155 for two reasons:

1. It's based on the latest master branch until noontime on Jan.29th, 2022. I can leverage PR Add ui.data(), ctx.data(), ctx.options() and ctx.tessellation_options() #1175 to manipulate the bezier_tolerance.
2. better formatting.

[emilk]

Looks great! But there are still the clippy warnings to silence, and you need to run cargo fmt. If you make the PR collaborative I can help you fix it!

[xudesheng]

Thank you @emilk, I fixed all Clippy warnings. I learned more from this journey. 👍 Kindly please review it again and hopefully there is a better solution for the code between lines 64-68 in paint_bezier.rs to have a widget that can manipulate the tasseller options.

[xudesheng]

Hi, @emilk Clippy is still reporting some error message but it seems like it is aginst the old commit. None of them exists in the current latest commit now. How shall I do the next step? sorry since this is almost my "first" PR. :-)

[emilk]

Hi, @emilk Clippy is still reporting some error message but it seems like it is aginst the old commit. None of them exists in the current latest commit now. How shall I do the next step? sorry since this is almost my "first" PR. :-)

If you run cargo clippy --all-targets you should see a few issues, starting with:

❯ cargo clippy --all-targets
    Checking egui v0.16.1 (/Users/emilk/code/egui/egui)
    Checking web-sys v0.3.55
warning: calls to `push` immediately after creation
   --> epaint/src/bezier.rs:758:9
    |
758 | /         let mut result = Vec::new();
759 | |         result.push(curve.points[0]); //add the start point
    | |_____________________________________^ help: consider using the `vec![]` macro: `let mut result = vec![..];`
    |
note: the lint level is defined here
   --> epaint/src/lib.rs:12:5
    |
12  |     clippy::all,
    |     ^^^^^^^^^^^
    = note: `#[warn(clippy::vec_init_then_push)]` implied by `#[warn(clippy::all)]`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#vec_init_then_push



```

[xudesheng]

cargo clippy --all-targets

Aha, all from the test code in the bezier.rs file. Thank you, I just fixed all of them and committed.

[emilk]

Thank you!

[4JX]

This PR introduces a typo, bezier_tolerence (Should be tolerance). It is present in tesellator.rs and introspection.rs.

[xudesheng]

Thank you, @4JX , you are right. I can submit a new PR to fix them if @emilk thinks it's worth a dedicated PR.