mobile: synthesised tap uses localFocalPoint, not focalPoint (follow-up to #163)#168
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Fixes a bug introduced by this same patch: the synthesised tap was dispatched with `event.focalPoint`, which Flutter documents as *global* coordinates (relative to the screen / Flutter window). `TouchEvent.localPosition` consumers — most importantly `View.pick(x, y, …)` — expect coordinates relative to the rendered viewport, not the entire screen. Whenever the ThermionWidget wasn't anchored at (0, 0) on screen (i.e. every realistic layout: anything inside a Scaffold body, a ListView, a Padding, etc.), picks landed outside the viewport and the result handler always returned the background entity. Symptom on Android: region clicks did nothing in any layout that nested the viewer below an AppBar / inside a list. iOS / macOS hadn't been hit yet because the spike author's iOS test layout happened to have the viewer near the screen origin. Fix: capture `event.localFocalPoint` (widget-relative) into `_scaleStartFocal`, and compare with `event.localFocalPoint` in onUpdate so the tap-vs-drag movement threshold is also computed in widget-local space. The `inputHandler.handle(ScaleStart/Update Event(localFocalPoint: …))` calls keep passing `event.focalPoint` (global) since that matches the upstream convention used elsewhere in this file for those events — and those events are consumed by orbit-camera code that uses deltas, not absolute positions, so the global/local distinction doesn't affect them. Doesn't change behaviour for any caller that doesn't use the synthesised tap (orbit, pinch-zoom, double-tap detection's duration-based half is already correct).
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Follow-up to #163
`#163` introduced the eager-scale gesture recognizer that synthesises tap and double-tap from the scale callbacks. The synthesis captured `event.focalPoint` from `ScaleStartDetails` and dispatched it as `TouchEvent.localPosition`. Flutter documents `focalPoint` as global (screen) coordinates; `TouchEvent.localPosition` consumers — most importantly `View.pick(x, y, …)` — expect coordinates relative to the viewport.
The result: in any layout where the Thermion widget isn't anchored at the screen origin (anything inside an AppBar / inside a list / inside padding), picks land outside the rendered viewport and Filament returns the background entity. Reproduced reliably on Android — the spike author's downstream app couldn't get region-tap to work in any non-trivial composition.
Fix
Capture `event.localFocalPoint` (widget-relative) into `_scaleStartFocal`, and use `event.localFocalPoint` in the onUpdate movement-distance comparison so the tap-vs-drag threshold is also computed in widget-local space.
The other places that pass `event.focalPoint` to `inputHandler.handle(ScaleStart/UpdateEvent(localFocalPoint: …))` keep using `event.focalPoint` (global) — that's the existing upstream convention for those events, and they're consumed by orbit-camera code that uses deltas, not absolute positions, so the global/local distinction doesn't affect them.
Why it didn't surface earlier
Initial testing happened in layouts where the viewer sat near the screen origin (top-left, full-width column). Global ≈ local in that case, picks landed on the right entity by coincidence. Moving the viewer into a real composition (e.g., a stress-test ListView on Android) immediately exposed the bug.
Verification