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Skip spring integration on non-finite or non-positive frame durations - #2
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thebrowsercompany-bot2 wants to merge 35 commits into
Open
Skip spring integration on non-finite or non-positive frame durations#2thebrowsercompany-bot2 wants to merge 35 commits into
thebrowsercompany-bot2 wants to merge 35 commits into
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I was erroneously assuming that ignoring velocity was sufficient to stop upon reaching the `toValue`, however with enough velocity, the check for whether `toValue` has been reached or not is incorrect. Now, it checks to see if the delta between the current value and the value after executing the spring to see if there’s a sign change (i.e. crossing zero), meaning the `toValue` has been reached and the spring should resolve.
This adds the ability to get the destination for a `DecayAnimation`. It also allows the ability to set the destination for a `DecayAnimation` (similar to how one can with `UIScrollView`). Setting the `toValue` on a `DecayAnimation` will result in the `velocity` being adjusted so that the `DecayAnimation` will stop at the supplied `toValue`. This also adds the ability to adjust how the decay will end with regards to rounded values. Setting a value of 1.0 will result in the `DecayAnimation` always stopping on whole point values (whereas setting something like `1 / screenScale` will allow it to stop on pixel values). Implements b3ll#28
Support toValue on DecayAnimation; Add roundingFactor
…bserve Pause animation driver if necessary when unobserving animations
Introduce AnimationEnvironment to address b3ll#18
Fixed a crash on tvOS if the device’s refresh rate was set below 60fps.
A display link that restarts after screen sleep/wake can deliver a non-finite or non-positive frame duration. Feeding that into the spring solver produces non-finite state, which traps when the value is read back on the next tick. Guard against it by skipping degenerate frames.
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Root Cause
On macOS,
CoreVideoDriverfeedsframe.duration(targetTimestamp - timestamp, derived fromCVTimeStamp.videoTime / videoTimeScale) straight intoSpringAnimation.tick. When the display link is torn down and restarted (e.g. after the screen sleeps and wakes), the first frame after wake can carry a non-finite or non-positive duration (a stale/zerovideoTimeScaleyieldsinf/NaN). Feeding that into the analytic spring solver produces non-finite state, which then traps when the value is read back.Fix
Guard
SpringAnimation.tickagainst non-finite and non-positive frame durations by skipping the frame. Finite durations — including large but valid ones — are unchanged, so normal playback is unaffected.Tests
Added
testSpringToleratesDegenerateFrameDuration, which ticks with zero, negative,inf, andNaNdurations and asserts the value/velocity stay finite. It fails on the pre-fix code and passes with the guard. FullMotionTestssuite passes (34 tests).This branch is
b3ll/Motion@c9a57f9(the commit currently pinned by the arc repo) plus this single fix.