[aborziak-ms]

Implemented After Effects algorithm for "Round Corners" effect. (There is a comment in Shapes.cs:634 that mentioned this // TODO - can round corners be implemented by composing cubic Beziers?)

For now I added support only for one-path + no-animations scenario, in following PR will also add support for multiple paths and animated path/radius. Just to keep this PR small.

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To make a round corner we are stepping radius pixels in both directions from the corner, and joining resulting points together with a bezier curve (MakeCubicBezier takes 3 points and creates a bezier curve). But also there is a tricky case, when one end of the segment is already curved, this case described on picture 2.

Algorithm loops over segments and creates new array of segments, there are several cases that can happen when we are processing current segment:
0 If current segment has both ends curved we do not need to change anything, just add current segment to the result
1 If current segment has both ends that are not curved:

On this step we are creating new segments (prevControlPoint, point0) and (point0, point1)

2 If current segment has first end curved:

New point will be created on distance radius from the second end of the segment, on the line that connects second end of the segment and controlPoint1 of original bezier curve

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Here how it looks in lottie (it is pixel-perfect with how it looks in After Effects) :

(red - original shape, green - with round corners)

[eliezerpMS]

[eliezerpMS]

[eliezerpMS]