crash in IOS graphics - probably a regression

[ddyer0]

I stumbled into this while trying to produce a test case for a problem I saw on IOS,
but it's not the problem I was trying to produce. This uses a fairly simple sequence
of translation and clipping of polygons. The intended result is like this frame, produced
on android.

on IOS (with metal=false) this starts producing what looks correct frames, but crashes after 20 or
21 frames. Final frame looks like this:

here's the test program

Dtest.java

[ddyer0]

ok, going to the next step I see that the test program has a bug - there's 1 excess pushClip per cycle.
But since these cycles are independent - from a different call to paint and a different gc, the excess 1
push should be harmless.

[shai-almog]

We no longer support metal=false and won't fix non-crucial bugs there.

[ddyer0]

also crashes with metal=true. The demo's bug us that an unmatched pushClip exists, your
bug is that this persists into the next paint and crashes after 20 reps.

[ddyer0]

the polygon/translate bug I was chasing seems to be a non-metal regression. Metal builds don't exhibit it.
I was planning to make at least one more non-metal IOS release because of #4907, which is the only metal-related
bug that still affects my apps. Be advised that I'm pretty sure you've introduced an IOS regression that manifests
as unfilled polygons.

[shai-almog]

I added a few PRs that addressed some rendering bugs over the past few days e.g. #5049 so it might address the clipping issue.

[ddyer0]

the current builds have significant problems related to #3921 . i added a clip.

[ddyer0]

This is not fixed in the public release built an hour ago. It's been 10 hours since the repo noted a release.

[shai-almog]

The fix made here was a simulator warning and failure when you do a push/pop clip that's unbalanced. The clipping issue discussed should only be fixed in the metal pipeline which should now be the default. If metal output != simulator that is something I would like to know about. If it's OpenGL then this is already deeply deprecated by Apple and probably not worth the time investigating.