readest/apps/readest-app/.claude/memory/middle-click-autoscroll-4951.md

name, description, metadata

name	description	metadata
middle-click-autoscroll-4951	Middle-click autoscroll in scrolled mode (#4951): Autoscroller RAF core + armed-books registry in iframeEventHandlers; scrolls via renderer.containerPosition	node_type type originSessionId memory project d8d21fc2-b63b-4f65-8ca8-f65d9e6b17b2

Middle mouse button autoscroll for desktop Tauri apps in scrolled mode (readest#4951), PR #4955 MERGED 2026-07-06 (merge 6f3b401c2). No settings toggle: always on for desktop in scrolled mode (maintainer removed the toggle as unnecessary; middle click has no other use in the reader). The same PR also shipped a locale sync: 69 keys untranslated on main filled across 33 locales (agents per language family; scanner-prunable keys preserved).

Key structure:

• src/app/reader/utils/autoscroller.ts — pure Autoscroller class (RAF loop, 12px dead zone, 10 px/s per px linear velocity capped 4000, whole-pixel emission with fractional carry, held→sticky/drag state machine). Tested in src/__tests__/reader/utils/autoscroller.test.ts with injected raf/now.
• useMiddleClickAutoscroll(bookKey, viewRef, containerRef) hook consumes iframe-mousedown/mouseup/mousemove/wheel/keydown messages + window-level capture listeners; returns anchor (container-relative) for AutoscrollIndicator. Scrolls with renderer.containerPosition += delta (public setter; native scroll path, so section preloading works). Axis from renderer.scrollProp ('scrollLeft' = vertical writing → x axis; increasing scrollLeft always moves viewport right even in RTL, no special-casing).
• iframeEventHandlers runs in the parent realm: setAutoscrollArmed(bookKey) registry lets handleMousedown preventDefault middle button (suppresses WebView2's native autoscroll on Windows, avoids double-drive) and handleAuxclick swallow link opens; setAutoscrollTracking(bool) gates an iframe-mousemove postMessage forwarder so it costs nothing when idle.
• Pointer deltas use screenX/Y (same trick as useTouchEvent pinch) so iframe coordinate spaces/transforms don't matter. Anchor window position computed in the iframe handler via event.view.frameElement.getBoundingClientRect() + client-size scale, posted as windowX/windowY on button-1 mousedown only.
• A left click that ends a sticky session must not also turn the page: the hook consumes the later iframe-single-click via eventDispatcher.onSync within a 500ms window (usePagination checks dispatchSync consumption before paginating).
• Setting middleClickAutoscroll in BookLayout (default TRUE, user chose default-on), toggle in ControlPanel Scroll BoxedList, desktop only (appService?.isDesktopApp), disabled unless scrolled mode. Web excluded on purpose (browsers own middle click).

Related: i18n-extract-prunes-keys (followed its manual single-key insertion recipe for the 'Middle-Click Autoscroll' label across 33 locales).