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Add follow head toggle to fork choice viz #344

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Merged
pablodeymo merged 4 commits into from
May 6, 2026
+113 −6
Merged

Add follow head toggle to fork choice viz #344

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d76f370
Add follow head toggle to fork choice viz
dicethedev May 4, 2026
005e98e
Update crates/net/rpc/static/fork_choice.html
dicethedev May 4, 2026
d8738ab
Update crates/net/rpc/static/fork_choice.html
dicethedev May 4, 2026
95943b5
Merge branch 'main' into fix/fork-choice-follow-head-toggle
MegaRedHand May 5, 2026
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119 changes: 113 additions & 6 deletions crates/net/rpc/static/fork_choice.html
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,28 @@
gap: 2px;
}

#follow-head-toggle {
margin-left: auto;
padding: 7px 12px;
border: 1px solid #ff9800;
border-radius: 4px;
background: transparent;
color: #ff9800;
font-family: "Courier New", Courier, monospace;
font-size: 12px;
font-weight: bold;
cursor: pointer;
}

#follow-head-toggle:hover {
background: rgba(255, 152, 0, 0.12);
}

#follow-head-toggle[aria-pressed="false"] {
border-color: #666;
color: #aaa;
}

.value-head { color: #ff9800; }
.value-justified { color: #2196f3; }
.value-finalized { color: #4caf50; }
Expand Down Expand Up @@ -157,6 +179,7 @@
<span class="label">Validators</span>
<span class="value value-validators" id="validator-count">--</span>
</div>
<button id="follow-head-toggle" type="button" aria-pressed="true">Following Head</button>
</div>

<div id="chart-container">
Expand Down Expand Up @@ -185,9 +208,15 @@
const container = document.getElementById("chart-container");
const tooltip = document.getElementById("tooltip");
const emptyMsg = document.getElementById("empty-message");
const followHeadToggle = document.getElementById("follow-head-toggle");

let svg, gLinks, gNodes, gAxis;
let currentData = null;
let followHead = true;
let currentHeadScrollTarget = null;
let lastScrollTop = 0;
let programmaticScrollTimeout = null;
let isProgrammaticScroll = false;

function initSVG() {
svg = d3.select("#chart-container")
Expand Down Expand Up @@ -359,6 +388,50 @@
tooltip.style.opacity = 0;
}

function updateFollowHeadToggle() {
followHeadToggle.setAttribute("aria-pressed", String(followHead));
followHeadToggle.textContent = followHead ? "Following Head" : "Follow Head";
}

function markProgrammaticScroll() {
isProgrammaticScroll = true;
if (programmaticScrollTimeout) clearTimeout(programmaticScrollTimeout);
programmaticScrollTimeout = setTimeout(() => {
isProgrammaticScroll = false;
}, TRANSITION_DURATION + 150);
}

Comment on lines +399 to +403
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@greptile-apps greptile-apps Bot May 4, 2026

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P2 Heuristic timeout may misclassify browser scroll events

isProgrammaticScroll is reset after TRANSITION_DURATION + 150 ms (650 ms), but CSS smooth-scroll duration is browser-controlled and not guaranteed to match TRANSITION_DURATION. On slow devices or with large scroll distances, the animation can easily exceed 650 ms, causing the tail-end scroll events to be treated as user-initiated. If those events happen to reduce scrollTop (e.g. scroll target is above current position), setFollowHead(false) could fire spuriously while the programmatic scroll is still completing.

Prompt To Fix With AI 
This is a comment left during a code review.
Path: crates/net/rpc/static/fork_choice.html
Line: 399-403

Comment:
**Heuristic timeout may misclassify browser scroll events**

`isProgrammaticScroll` is reset after `TRANSITION_DURATION + 150` ms (650 ms), but CSS smooth-scroll duration is browser-controlled and not guaranteed to match `TRANSITION_DURATION`. On slow devices or with large scroll distances, the animation can easily exceed 650 ms, causing the tail-end scroll events to be treated as user-initiated. If those events happen to reduce `scrollTop` (e.g. scroll target is above current position), `setFollowHead(false)` could fire spuriously while the programmatic scroll is still completing.

How can I resolve this? If you propose a fix, please make it concise.

function scrollToHead(behavior = "smooth") {
if (currentHeadScrollTarget == null) return;
markProgrammaticScroll();
container.scrollTo({
top: currentHeadScrollTarget,
behavior
});
}

function isAtHead() {
return currentHeadScrollTarget != null &&
Math.abs(container.scrollTop - currentHeadScrollTarget) <= NODE_RADIUS * 3;
}

function setFollowHead(enabled, shouldScroll = false) {
followHead = enabled;
updateFollowHeadToggle();

if (followHead && shouldScroll) {
scrollToHead();
}
}

function markUserScrollIntent() {
isProgrammaticScroll = false;
if (programmaticScrollTimeout) {
clearTimeout(programmaticScrollTimeout);
programmaticScrollTimeout = null;
}
}

function render(data) {
if (!data || !data.nodes || data.nodes.length === 0) {
emptyMsg.style.display = "block";
Expand Down Expand Up @@ -516,16 +589,22 @@
if (hovered) tooltip.innerHTML = tooltipHtml(hovered, data.validator_count);
}

// Auto-scroll to head node
// Auto-scroll to head node if head tracking is enabled.
const headNode = layout.nodes.find(n => n.root === data.head);
if (headNode) {
const containerRect = container.getBoundingClientRect();
const headY = headNode.y;
const scrollTarget = headY - containerRect.height / 2;
container.scrollTo({
top: Math.max(0, scrollTarget),
behavior: "smooth"
});
const maxScrollTop = Math.max(0, layout.height - containerRect.height);
currentHeadScrollTarget = Math.min(
maxScrollTop,
Math.max(0, headY - containerRect.height / 2)
);

if (followHead) {
scrollToHead();
}
} else {
currentHeadScrollTarget = null;
}
}

Expand All @@ -547,9 +626,37 @@
}

initSVG();
updateFollowHeadToggle();
fetchAndRender();
setInterval(fetchAndRender, POLL_INTERVAL);

followHeadToggle.addEventListener("click", () => {
setFollowHead(!followHead, true);
});

container.addEventListener("scroll", () => {
const scrollingUp = container.scrollTop < lastScrollTop - 2;

if (!isProgrammaticScroll) {
if (followHead && scrollingUp && !isAtHead()) {
setFollowHead(false);
} else if (!followHead && isAtHead()) {
setFollowHead(true);
}
}

lastScrollTop = container.scrollTop;
});

container.addEventListener("wheel", markUserScrollIntent, { passive: true });
container.addEventListener("pointerdown", markUserScrollIntent, { passive: true });
container.addEventListener("touchstart", markUserScrollIntent, { passive: true });
window.addEventListener("keydown", event => {
if (["ArrowUp", "ArrowDown", "PageUp", "PageDown", "Home", "End", " "].includes(event.key)) {
markUserScrollIntent();
}
});
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window.addEventListener("resize", () => {
if (currentData) render(currentData);
});
Expand Down