tree 3af8c35e0adf9ee1297dab8f75421214c49e7ff5
parent d3efa999af6d85033ba6af9a96b18f204c73d31b
author Mike Reed <reed@google.com> 1543410821 +0000
committer Skia Commit-Bot <skia-commit-bot@chromium.org> 1543410823 +0000

Revert "don't trust convexity with affine transforms"

This reverts commit 26d8d77aae56c20b7174ac06056c1e5ec7903e6b.

Reason for revert: speculative, in case this is blocking the chrome roll

Original change's description:
> don't trust convexity with affine transforms
> 
> In theory, a convex shape transformed by an affine matrix should still
> be convex. However, due to numerical nastiness of floats, when we try
> to determine if something is convex, we can get different answers pre
> and post a transformation (think of two line segments nearly colinear).
> 
> Convex paths take a faster scan converter, but it is only well behaved
> if the path is, in fact, convex. Thus we have to be conservative about
> which paths we mark as convex.
> 
> This bug found a case where a "convex" path, after going through a transform,
> became (according to our measure) non-convex. The bug was that we *thought*
> that once convex always convex, but in reality it was not. The fix (hack) is
> to notice when we transform by an affine matrix (we're still assuming/hoping
> that scaling and translate keep things convex (1)...) and mark the convexity
> as "unknown", forcing us to re-compute it.
> 
> This will slow down these paths, since it costs something to compute convexity.
> Hopefully non-scale-translate transforms are rare, so we won't notice the
> speed loss too much.
> 
> (1) This is not proven. If we find scaling/translation to break our notion of
> convexity, we'll need to get more aggressive/clever to find a fix.
> 
> 
> Bug: 899689
> Change-Id: I5921eca247428bf89380bc2395fe373fa70deb1d
> Reviewed-on: https://skia-review.googlesource.com/c/173080
> Commit-Queue: Mike Reed <reed@google.com>
> Reviewed-by: Cary Clark <caryclark@google.com>
> Reviewed-by: Jim Van Verth <jvanverth@google.com>

TBR=mtklein@google.com,jvanverth@google.com,caryclark@google.com,reed@google.com,caryclark@skia.org

Change-Id: I5d846798f2c34c6576591a3c3125cfdc3c72dbdc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 899689
Reviewed-on: https://skia-review.googlesource.com/c/173162
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>