fix: reduce live view scroll sensitivity#188
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Replace the old throttle-and-clamp scroll handler with a fixed-rate polling approach that sends at most 1 scroll tick per 100ms interval in each direction. This dramatically reduces scroll speed for both mouse wheel and trackpad input: - Mouse wheel: 1 notch now sends 1 tick (~120px) instead of 7-10 ticks - Trackpad: max 10 ticks/sec instead of 60-100 ticks/sec - Accumulated deltas are tracked with a jitter threshold to filter noise - Interval auto-cleans when scroll input stops Also lower the default scroll sensitivity from 10 to 3. Made-with: Cursor
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The scroll slider (1–100) now controls the polling interval: - scroll=1 → 200ms interval (5 ticks/sec, slowest) - scroll=10 → 185ms interval (5.4 ticks/sec, default) - scroll=50 → 117ms interval (8.5 ticks/sec) - scroll=100 → 33ms interval (30 ticks/sec, fastest) Restore default scroll to 10 (the original value) since the setting is now meaningful again. Made-with: Cursor
Made-with: Cursor
Reintroduce magnitude-aware tick calculation so fast scrolling feels responsive. Accumulated pixel deltas are divided by 120 (one Chromium scroll-notch worth of pixels) and clamped by the scroll setting. Slow scroll (1 notch ≈ 100px) still produces 1 tick; fast scroll (500px accumulated) now produces ~4 ticks instead of always 1. Made-with: Cursor
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| const scaleAxis = (delta: number): number => { | ||
| if (Math.abs(delta) < JITTER_THRESHOLD) return 0 | ||
| const ticks = delta / PIXELS_PER_TICK | ||
| const clamped = Math.min(Math.max(Math.round(ticks), -this.scroll), this.scroll) |
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Missing default scroll change undermines sensitivity fix
Medium Severity
The scaleAxis function clamps tick count to this.scroll, and the PR description states the default was lowered from 10 to 3 in settings.ts, but that companion change is missing from this commit. With the existing default of 10, scaleAxis allows up to 10 ticks per interval (~6480 px/sec max) instead of the intended 3 ticks (~1800 px/sec), largely defeating the purpose of capping trackpad scroll speed.
| this.pendingScrollX += x | ||
| this.pendingScrollY += y |
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The core issue here is that the old code clamped raw pixel deltas
(~100px per notch) directly as tick counts — that's the 10x multiplier bug. This can be fixed much more simply by dividing by 120 (pixels per Chromium
scroll notch) in the existing code path:
x = x === 0 ? 0 : Math.min(Math.max(Math.round(x / 120) || Math.sign(x), -this.scroll), this.scroll)
y = y === 0 ? 0 : Math.min(Math.max(Math.round(y / 120) || Math.sign(y), -this.scroll), this.scroll)That keeps the existing throttle and avoids the interval/accumulation/cleanup
machinery. I wonder if starting with a more minimal fix and only adding complexity based on testing would be easier for us long term ^^
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Good call — you're right that the core bug is just a missing divisor, and the interval/accumulation machinery is unnecessary complexity to solve it. Simplifying to your approach now.
Replace the interval/accumulation machinery with a one-line fix per Sayan's review: divide raw pixel deltas by 120 (one Chromium scroll notch) before clamping. Keeps the existing throttle, avoids interval lifecycle complexity. Old: 100px delta → clamped to 10 → 10 XButton events → 1200px scroll New: 100px delta → 100/120 = 1 → 1 XButton event → 120px scroll Made-with: Cursor
| // Note that if deltamode is line or page won't matter since we aren't | ||
| // sending the mouse wheel delta to the server anyway. | ||
| // The difference between pixel and line can be important however since | ||
| // we have a threshold that can be smaller than the line height. |
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this comment seems useful? and maybe should be expanded with the change in this pr
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Good catch — restored the comment and expanded it to explain the PIXELS_PER_TICK divisor, the 1:1 mapping to XTestFakeButtonEvents, and how the scroll setting clamps fast swipes.
Adds back the removed deltaMode/pixel comment and expands it to explain the PIXELS_PER_TICK divisor and scroll clamp. Made-with: Cursor
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Checklist
Summary
Users (Nava, Gabe) reported that live view scrolling is too sensitive/fast. The root cause is that the old scroll handler clamped raw pixel deltas directly to the
scrollsetting (default 10), meaning a single mouse wheel notch (~100px) would send 10 XTestFakeButtonEvent clicks to Chromium — each scrolling ~120px, totaling ~1200px per notch.This PR replaces the old throttle-and-clamp approach with a fixed-rate polling scroll handler that:
Before vs After
Also lowers the default scroll sensitivity setting from 10 to 3.
Files changed
images/chromium-headful/client/src/components/video.vue— new scroll handlerimages/chromium-headful/client/src/store/settings.ts— lower default scroll valueTest plan
build-docker.shand run withrun-docker.sh(ENABLE_WEBRTC=true)Made with Cursor
Note
Medium Risk
Changes how wheel input is converted into remote scroll events; small logic errors could make scrolling feel broken or inverted on some devices/browsers, but scope is limited to the client wheel handler.
Overview
Reduces live-view scroll sensitivity by changing
video.vue’sonWheelhandler to normalize wheel deltas to pixel units (handling non-zerodeltaMode) and then convert pixel deltas into discrete scroll “ticks” (≈120px per tick) before applying the userscrollclamp.This replaces the previous direct clamp of raw deltas, aiming to prevent trackpads/fast wheel gestures from generating excessive remote scroll events while preserving invert-scroll behavior.
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