Created attachment 468406 [details] photo of the issue See this codepen: https://codepen.io/_-0-_/pen/RwvaPNN). When clipping a filtered WebGL canvas element the filter seems to be calculated from the clipped area instead of from the element's box. This does happen only for when there is a WebGL canvas inside the filtered content, i.e. when the canvas requests a 2D context, it works as expected. Also, it seems the filter is applied once more on the <body> tag, as can be seen when shrinking the frame vertically in the liked demo. And one more peculiarity, trying to take a screenshot (macOS "Screenshot" app), the bug disappears from the screenshot, so I attach a photo of what I see, and beware that automated tests may be incorrect.
<rdar://problem/117697558>