The browser delivers one large quantised delta per wheel notch, which
Chromium scrolls without interpolation — producing the jerky one-step
motion reported on Windows. Detect mouse-wheel-shaped events inside
the iframe (line-mode, or single-axis with |deltaY| ≥ 50), suppress
the native scroll, and replay the delta as an rAF exponential lerp on
the renderer's container. Trackpad / high-resolution input is left to
native scrolling so its momentum and 2-axis behaviour are preserved.
Huang Xin
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