[romchornyi]

Issue being fixed or feature implemented

Closes #25.

ScrollViewWithOnScrollChanged measured its scroll offset with a zero-size LocationReader placed as the first child of the content, inside a per-instance named coordinate space. The reason was that onScrollGeometryChange wasn't available. It is available at the iOS 18 / macOS 15 floor set by #15. The type is public API, so it stays with the same signature and is reimplemented on the system API.

What was done?

• The offset comes from onScrollGeometryChange, computed by an internal scrollContentOrigin(of:layoutDirection:). The named coordinate space and the probe are gone.
• The y value is unchanged. It is .zero at rest, negative while scrolled, and positive while pulled past the start.
• x is now the real offset. Before, it was the probe's position, which was the centre of the content (for example 1230 = half the content width at rest in a horizontal view). In right-to-left layouts ScrollGeometry reports the horizontal axis differently: at rest contentOffset.x equals the trailing inset, and the leading inset does not move it. The function handles this, and tests cover it.
• A zero-size Color.clear stays as the first child. The probe added one default stack spacing above the content, and hosts lay out against it. Removing it would move their content up.
• The last value is sent again when the content reappears with its state kept. The probe's onAppear did the same. On first appearance exactly one value is sent.
• LocationReader / readingLocation were internal, and the probe was their only caller, so the file is deleted. Docs and README no longer list readingLocation.
• Previews cover vertical, vertical with a top margin, horizontal, and horizontal right-to-left.

How Has This Been Tested?

• swift build, swift test (23 tests, 7 of them new in ScrollContentOriginTests) and xcodebuild build-for-testing for the iOS Simulator are clean.
• Master and this branch were measured side by side on an iOS 27 simulator. A test bundle hosted the view in a UIWindow, set contentOffset on the real UIScrollView, and recorded every reported value. y is identical in every case below:

Situation	master y (rest / +120 / −40)	branch y
no inset	0 / −120 / 40	same
112pt top safe-area inset	0 / −120 / 40	same
safeAreaPadding(.top, 20)	0 / −120 / 40	same
ignoresSafeArea()	0 / −120 / 40	same
nested horizontal carousel scrolled	0 reports from the carousel	same
large title collapsing (inset 168 → 116)	−20 / −52 / −48 / −148	same
.refreshable while refreshing	−60	same
content's first child at	8pt (Color first), 6.43pt (Text first)	same
reappear (tab switch back)	1 re-report, current value	same

• x on the branch reads 0 at rest, goes negative towards the end, and positive past the start. That holds in LTR (with a leading or trailing inset) and in RTL (with a start inset, an end inset, or contentMargins(.horizontal, 20)), and for a vertical RTL view with horizontal margins. The unit tests use the raw ScrollGeometry values captured in those runs.
• The only consumer, dashwallet-ios LocalCurrencyView, reads min(offset.y, 0) and uses no contentMargins, so it sees no change.

Breaking Changes

No API change: the signature is the same, and the API check covers it. The reported values change in two cases:

• x: it is now the scroll offset instead of the content centre. Nothing reads x today.
• contentMargins: y at rest is now 0. Before, it was the margin, because the probe sat inside the margin. With safe-area insets and safeAreaPadding, y at rest was already 0, and it still is.

Not handled and not measured, both are edge cases:

• Layout direction flipped at runtime while the view is at rest: x updates only on the next geometry change.
• Geometry changes while the view is hidden: on reappear the host first gets the last value seen, then the new one. Master sent only the current value.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

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