GeezerVison

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the CLA.
• All existing tests are passing: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/DevelopmentWorkflow.md#running-unit-tests-application.
• Tests for the changes are included - https://github.com/NativeScript/NativeScript/blob/master/tools/notes/WritingUnitTests.md.

What is the current behavior?

A keyframe animation plays its first keyframe as a jump and holds its last one. When the keyframes leave out 0% or 100%, the animation does not behave as in CSS, where the element's own values fill the missing ends:

• @keyframes spin { to { transform: rotate(360deg) } } jumps to 360° on every iteration, so the spinner never turns (Bootstrap's spinner-border, Tailwind's animate-spin).
• Keyframes that stop at 50% never come back (Bootstrap's spinner-grow).

What is the new behavior?

KeyframeAnimation.keyframeAnimationFromInfo() adds the missing 0%/100% keyframe, and play() fills it with the view's own values for the properties the other keyframes animate (rotate, scale, translate, opacity, background color, width, height). An auto width or height, which cannot be animated from, is left out. The KeyframeAnimationInfo passed in is not modified.

Tests: ui/animation/keyframe-animation.spec.ts (6).

Verified with all of these core PRs merged together (#11527–#11537): apps/automated passes on the iOS 26.4 simulator (1830 OK, 0 failed) and on an Android API 36 emulator (1692 OK; the one failure is the network-dependent IMAGE-CACHE.test_ImageCache_ValidUrl timeout, which also passes on reruns).