feat(messages): collapse reactions to one row with a +N chip (#138)

Many distinct reactions used to wrap into a tall stack (16 reactions =
4 rows at phone width). Now only the first row is shown, ending in a
"+N" chip; tapping it expands inline and a "less" chip collapses again.
Expanded state is remembered per message for the session. Nothing changes
when the reactions already fit on one row.

Overflowing chips stay in the DOM (invisible, aria-hidden, untabbable,
clipped by max-height) so the container keeps its natural width — which
keeps shrink-to-fit bubble layout stable — and each chip stays measurable.
utils/reactionOverflow.ts holds the unit-tested fit calculation; a
ResizeObserver re-fits on width changes. "+N" is forced LTR for RTL UIs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/room/message/Reactions.tsx

@@ -1,4 +1,11 @@
-import React, { MouseEventHandler, useCallback, useState } from 'react';
+import React, {
+  MouseEventHandler,
+  useCallback,
+  useEffect,
+  useLayoutEffect,
+  useRef,
+  useState,
+} from 'react';
 import {
   Box,
   Modal,
@@ -23,6 +30,7 @@ import * as css from './styles.css';
 import { ReactionViewer } from '../reaction-viewer';
 import { stopPropagation } from '../../../utils/keyboard';
 import { useMediaAuthentication } from '../../../hooks/useMediaAuthentication';
+import { expandedReactionMessages, fitReactionRow } from '../../../utils/reactionOverflow';
 
 export type ReactionsProps = {
   room: Room;
@@ -42,6 +50,49 @@ export const Reactions = as<'div', ReactionsProps>(
       useCallback((rel) => [...(rel.getSortedAnnotationsByKey() ?? [])], []),
     );
 
+    // [Gitea #138] Collapse to one row + "+N" when the chips would wrap.
+    // Overflowing chips stay in the DOM (invisible, clipped by max-height) so
+    // the container keeps its natural width and every chip stays measurable.
+    const [expanded, setExpandedState] = useState(() => expandedReactionMessages.has(mEventId));
+    const setExpanded = (next: boolean) => {
+      if (next) expandedReactionMessages.add(mEventId);
+      else expandedReactionMessages.delete(mEventId);
+      setExpandedState(next);
+    };
+    const [limit, setLimit] = useState<number | undefined>();
+    const [rowHeight, setRowHeight] = useState<number | undefined>();
+    const containerRef = useRef<HTMLDivElement | null>(null);
+    const moreRef = useRef<HTMLButtonElement | null>(null);
+    const chipRefs = useRef(new Map<string, HTMLElement>());
+    const keys = reactions.map(([key]) => key).join('\u0000');
+
+    const measure = useCallback(() => {
+      const container = containerRef.current;
+      if (!container) return;
+      const rowWidth = container.getBoundingClientRect().width;
+      const gap = parseFloat(getComputedStyle(container).columnGap) || 8;
+      const chips = keys ? keys.split('\u0000').map((k) => chipRefs.current.get(k)) : [];
+      const widths = chips.map((el) => el?.getBoundingClientRect().width ?? 0);
+      const moreWidth = moreRef.current?.getBoundingClientRect().width ?? 48;
+      setLimit(fitReactionRow(widths, moreWidth, gap, rowWidth));
+      setRowHeight(Math.max(0, ...chips.map((el) => el?.getBoundingClientRect().height ?? 0)));
+    }, [keys]);
+
+    useLayoutEffect(() => {
+      measure();
+    }, [measure]);
+    useEffect(() => {
+      const container = containerRef.current;
+      if (!container || typeof ResizeObserver === 'undefined') return undefined;
+      const ro = new ResizeObserver(() => measure());
+      ro.observe(container);
+      return () => ro.disconnect();
+    }, [measure]);
+
+    const collapsed = !expanded && limit !== undefined;
+    const hiddenCount = collapsed ? reactions.length - (limit ?? 0) : 0;
+    const hiddenStyle: React.CSSProperties = { visibility: 'hidden', pointerEvents: 'none' };
+
     const handleViewReaction: MouseEventHandler<HTMLButtonElement> = (evt) => {
       evt.stopPropagation();
       evt.preventDefault();
@@ -56,44 +107,99 @@ export const Reactions = as<'div', ReactionsProps>(
         gap="200"
         wrap="Wrap"
         {...props}
-        ref={ref}
+        style={{
+          ...props.style,
+          ...(collapsed && rowHeight
+            ? // 2px breathing room so row-1 focus outlines are not clipped.
+              { maxHeight: rowHeight + 4, overflow: 'hidden', padding: 2, margin: -2 }
+            : {}),
+        }}
+        ref={(el) => {
+          containerRef.current = el;
+          if (typeof ref === 'function') ref(el);
+          else if (ref) (ref as React.MutableRefObject<HTMLDivElement | null>).current = el;
+        }}
       >
-        {reactions.map(([key, events]) => {
+        {reactions.map(([key, events], index) => {
           const rEvents = Array.from(events);
           if (rEvents.length === 0 || typeof key !== 'string') return null;
           const myREvent = myUserId ? rEvents.find(factoryEventSentBy(myUserId)) : undefined;
           const isPressed = !!myREvent?.getRelation();
+          const hidden = collapsed && index >= (limit ?? 0);
+          const chip = (targetRef?: React.RefCallback<HTMLElement>) => (
+            <Reaction
+              ref={(el: HTMLElement | null) => {
+                targetRef?.(el);
+                if (el) chipRefs.current.set(key, el);
+                else chipRefs.current.delete(key);
+              }}
+              data-reaction-key={key}
+              aria-pressed={isPressed}
+              key={key}
+              mx={mx}
+              reaction={key}
+              count={events.size}
+              onClick={canSendReaction ? () => onReactionToggle(mEventId, key) : undefined}
+              onContextMenu={handleViewReaction}
+              aria-disabled={!canSendReaction}
+              aria-hidden={hidden || undefined}
+              tabIndex={hidden ? -1 : undefined}
+              style={hidden ? hiddenStyle : undefined}
+              useAuthentication={useAuthentication}
+            />
+          );
+          // The "+N" chip sits right after the last visible chip so it lands on row 1.
+          const moreChip = index === (limit ?? 0) - 1 && (
+            <button
+              key="more"
+              ref={moreRef}
+              type="button"
+              className={css.ReactionsMore}
+              onClick={() => setExpanded(true)}
+              aria-expanded={false}
+              aria-label={`Show ${hiddenCount} more reactions`}
+              aria-hidden={!collapsed || undefined}
+              tabIndex={collapsed ? undefined : -1}
+              style={collapsed ? undefined : { ...hiddenStyle, position: 'absolute' }}
+            >
+              <Text as="span" size="T300" dir="ltr">
+                {`+${collapsed ? hiddenCount : reactions.length - 1}`}
+              </Text>
+            </button>
+          );
+          if (hidden) return <React.Fragment key={key}>{chip()}</React.Fragment>;
 
           return (
-            <TooltipProvider
+            <React.Fragment key={key}>
-              key={key}
+              <TooltipProvider
-              position="Top"
+                position="Top"
-              tooltip={
+                tooltip={
-                <Tooltip style={{ maxWidth: toRem(200) }}>
+                  <Tooltip style={{ maxWidth: toRem(200) }}>
-                  <Text className={css.ReactionsTooltipText} size="T300">
+                    <Text className={css.ReactionsTooltipText} size="T300">
-                    <ReactionTooltipMsg room={room} reaction={key} events={rEvents} />
+                      <ReactionTooltipMsg room={room} reaction={key} events={rEvents} />
-                  </Text>
+                    </Text>
-                </Tooltip>
+                  </Tooltip>
-              }
+                }
-            >
+              >
-              {(targetRef) => (
+                {(targetRef) => chip(targetRef)}
-                <Reaction
+              </TooltipProvider>
-                  ref={targetRef}
+              {moreChip}
-                  data-reaction-key={key}
+            </React.Fragment>
-                  aria-pressed={isPressed}
-                  key={key}
-                  mx={mx}
-                  reaction={key}
-                  count={events.size}
-                  onClick={canSendReaction ? () => onReactionToggle(mEventId, key) : undefined}
-                  onContextMenu={handleViewReaction}
-                  aria-disabled={!canSendReaction}
-                  useAuthentication={useAuthentication}
-                />
-              )}
-            </TooltipProvider>
           );
         })}
+        {expanded && limit !== undefined && (
+          <button
+            type="button"
+            className={css.ReactionsMore}
+            onClick={() => setExpanded(false)}
+            aria-expanded
+            aria-label="Show fewer reactions"
+          >
+            <Text as="span" size="T300">
+              less
+            </Text>
+          </button>
+        )}
         {reactions.length > 0 && (
           <Overlay
             onContextMenu={(evt: any) => {

src/app/features/room/message/styles.css.ts

@@ -1,5 +1,5 @@
 import { style } from '@vanilla-extract/css';
-import { DefaultReset, config, toRem } from 'folds';
+import { DefaultReset, FocusOutline, color, config, toRem } from 'folds';
 
 export const MessageBase = style({
   position: 'relative',
@@ -45,6 +45,7 @@ export const MessageMenuItemText = style({
 });
 
 export const ReactionsContainer = style({
+  position: 'relative',
   selectors: {
     '&:empty': {
       display: 'none',
@@ -52,6 +53,27 @@ export const ReactionsContainer = style({
   },
 });
 
+/** [Gitea #138] "+N" / "less" chip at the end of a collapsed reaction row. */
+export const ReactionsMore = style([
+  FocusOutline,
+  {
+    display: 'inline-flex',
+    alignItems: 'center',
+    flexShrink: 0,
+    padding: `${toRem(2)} ${config.space.S200}`,
+    color: color.SurfaceVariant.OnContainer,
+    backgroundColor: 'transparent',
+    border: `${config.borderWidth.B300} solid ${color.SurfaceVariant.ContainerLine}`,
+    borderRadius: config.radii.R300,
+    cursor: 'pointer',
+    selectors: {
+      '&:hover, &:focus-visible': {
+        backgroundColor: color.SurfaceVariant.ContainerHover,
+      },
+    },
+  },
+]);
+
 export const ReactionsTooltipText = style({
   wordBreak: 'break-word',
 });

src/app/utils/reactionOverflow.test.ts

@@ -0,0 +1,27 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { fitReactionRow } from './reactionOverflow';
+
+describe('fitReactionRow', () => {
+  it('returns undefined when everything fits', () => {
+    assert.equal(fitReactionRow([50, 50, 50], 40, 8, 166), undefined);
+    assert.equal(fitReactionRow([], 40, 8, 100), undefined);
+  });
+
+  it('leaves room for the +N chip', () => {
+    // 5 chips of 50 + 4 gaps = 282 > 200. 3 chips + gap + more = 150+16+8+40 = 214 > 200 → 2.
+    assert.equal(fitReactionRow([50, 50, 50, 50, 50], 40, 8, 200), 2);
+    // Wider row: 3 chips (166) + 8 + 40 = 214 ≤ 220 → 3.
+    assert.equal(fitReactionRow([50, 50, 50, 50, 50], 40, 8, 220), 3);
+  });
+
+  it('never hides every chip', () => {
+    assert.equal(fitReactionRow([90, 90], 40, 8, 100), 1);
+    assert.equal(fitReactionRow([200, 200], 40, 8, 100), 1);
+  });
+
+  it('handles uneven chip widths', () => {
+    // 30+8+80+8+30 = 156 > 150. 2 chips: 30+8+80 = 118, +8+40 = 166 > 150 → 1.
+    assert.equal(fitReactionRow([30, 80, 30], 40, 8, 150), 1);
+  });
+});

src/app/utils/reactionOverflow.ts

@@ -0,0 +1,26 @@
+/**
+ * [Gitea #138] How many reaction chips fit on one row next to a "+N" chip.
+ *
+ * Returns `undefined` when every chip fits on the first row (nothing to
+ * collapse). Otherwise returns the number of leading chips to show; the
+ * caller renders a "+N" chip after them. Always at least 1 chip.
+ */
+export function fitReactionRow(
+  chipWidths: number[],
+  moreChipWidth: number,
+  gap: number,
+  rowWidth: number,
+): number | undefined {
+  const rowLength = (count: number, extra: number) => {
+    let total = extra;
+    for (let i = 0; i < count; i += 1) total += chipWidths[i] + (i > 0 || extra > 0 ? gap : 0);
+    return total;
+  };
+  if (rowLength(chipWidths.length, 0) <= rowWidth) return undefined;
+  let count = chipWidths.length - 1;
+  while (count > 1 && rowLength(count, 0) + gap + moreChipWidth > rowWidth) count -= 1;
+  return count;
+}
+
+/** Session-only memory of which messages have their reactions expanded. */
+export const expandedReactionMessages = new Set<string>();