PDF viewer: mouse-wheel scrolling does not work on current Chromium (only legacy mousewheel/DOMMouseScroll are hooked)

[Timba90]

Summary

Mouse-wheel scrolling does not work in the PDF editor/viewer on current Chromium (tested with Edge 152.0.4191.53 and the matching WebView2 runtime). Dragging the scrollbar works; the wheel does nothing.

Cause

pdf/src/viewer.js (main @ d8a3d24, around line 1102) hooks only the legacy events:

_t.parent.onmousewheel = _t.onMouseWhell;
if (_t.parent.addEventListener)
    _t.parent.addEventListener("DOMMouseScroll", _t.onMouseWhell, false);

Chromium no longer dispatches the legacy mousewheel event, and DOMMouseScroll is Firefox-only. Measured with listeners on document during one wheel notch: {"mousewheel":0,"wheel":1,"wheelDelta":-120,"deltaY":600} — only wheel arrives, so onMouseWhell never runs.

The document editor is unaffected because it also registers a wheel listener elsewhere.

Fix that works

Register the same handler for wheel as well (the handler already reads the legacy wheelDelta* properties, which Chromium still populates on wheel events):

_t.parent.onmousewheel = _t.onMouseWhell;
_t.parent.addEventListener("wheel", _t.onMouseWhell, { passive: false });

With this patch applied to the built word/sdk-all.js, one wheel notch scrolls the PDF viewer by 45 px (same as the document editor), and the document editor still scrolls exactly once (no double registration there).

Environment

• Euro-Office/sdkjs main @ d8a3d24 (2026-08-27), built with npm run build, served with Euro-Office/web-apps main @ b8eb618b
• Chromium 152 (Edge and WebView2), Windows 11