3.8.3

Stop event banner size shifting

assets/css/base.css

@@ -257,18 +257,34 @@ body {
   background: rgba(0, 0, 0, 0.55);
 }
 
+/* Slide stack. Every active event is rendered and every slide is placed in the
+   same single grid cell, so the strip's height is set by the TALLEST slide and
+   stays put as the rotation cycles — a one-line event followed by a message
+   that wraps to two lines no longer grows the banner and shunts the page. */
+.event-note-stack {
+  display: grid;
+  grid-template-columns: minmax(0, 1fr);
+  align-items: start;
+  flex: 1;
+  min-width: 0;
+}
+
 .event-note-slide {
+  grid-area: 1 / 1;          /* stack all slides on top of each other */
   display: flex;
   align-items: baseline;
   flex-wrap: wrap;
   gap: 4px 10px;
-  flex: 1;
   min-width: 0;
-  opacity: 1;
+  opacity: 0;                /* only .is-active is visible */
+  pointer-events: none;
+  user-select: none;         /* keeps hidden copy out of a drag-selection */
   transition: opacity 0.35s ease;
 }
-.event-note-slide.is-fading {
-  opacity: 0;
+.event-note-slide.is-active {
+  opacity: 1;
+  pointer-events: auto;
+  user-select: auto;
 }
 
 .event-note-emoji {

assets/js/app.js

@@ -692,9 +692,18 @@ export function UTCIForecast() {
         const fmtDate = (iso) => iso
           ? new Date(iso + 'T00:00Z').toLocaleDateString('en-GB', { day: 'numeric', month: 'short', timeZone: 'UTC' })
           : null;
-        const startFmt = fmtDate(ev.start);
-        const peakFmt  = fmtDate(ev.peak);
-        const endFmt   = fmtDate(ev.end);
+        // Date line for one event — computed per slide because every event is
+        // rendered (see the stack below), not just the visible one.
+        const dateLineFor = (e) => {
+          const startFmt = fmtDate(e.start);
+          const peakFmt  = fmtDate(e.peak);
+          const endFmt   = fmtDate(e.end);
+          if (!startFmt || !endFmt) return null;
+          if (startFmt === endFmt) return peakFmt ? `Peak ${peakFmt}` : startFmt;
+          return (peakFmt && peakFmt !== startFmt && peakFmt !== endFmt)
+            ? `${startFmt} – ${endFmt} · Peak ${peakFmt}`
+            : `${startFmt} – ${endFmt}`;
+        };
         // Warning banners take their background from the day tabs' weather
         // palette (ev.tint, set in events/weather-checks.js) so a heat alert
         // reads the same orange as a hot day tab and a rain alert the same
@@ -709,21 +718,30 @@ export function UTCIForecast() {
             borderColor: `rgb(${ev.tint.map(c => Math.round(c * 0.72)).join(',')})`,
           };
         })() : undefined;
-        const dateLine = (startFmt && endFmt)
-          ? (startFmt === endFmt
-              ? (peakFmt ? `Peak ${peakFmt}` : startFmt)
-              : (peakFmt && peakFmt !== startFmt && peakFmt !== endFmt
-                  ? `${startFmt} – ${endFmt} · Peak ${peakFmt}`
-                  : `${startFmt} – ${endFmt}`))
-          : null;
         return html`
           <div class=${`event-note${isPriority ? ' is-priority' : ''}${noteTintStyle ? ' is-tinted' : ''}`} style=${noteTintStyle}>
             <span class="event-note-accent" style=${{ background: ev.color === '#fdf8ee' ? '#c8922a' : ev.color }} />
-            <div class=${`event-note-slide${noteFading ? ' is-fading' : ''}`}>
-              <span class="event-note-emoji">${ev.emoji}</span>
-              <span class="event-note-title">${ev.title}</span>
-              <span class="event-note-msg">${ev.message}</span>
-              ${dateLine && html`<span class="event-note-dates">${dateLine}</span>`}
+            ${/* Every slide is rendered, all stacked in one CSS grid cell, so the
+                strip is always as tall as the LONGEST event's copy. Rotating to
+                a two-line message then back no longer resizes the banner and
+                shunts the page up and down. Only the active slide is visible;
+                the rest sit at opacity 0 and are hidden from assistive tech. */''}
+            <div class="event-note-stack">
+              ${activeEvents.map((e, i) => {
+                const dateLine = dateLineFor(e);
+                const isActive = i === noteIndex && !noteFading;
+                return html`
+                  <div
+                    key=${e.id || i}
+                    class=${`event-note-slide${isActive ? ' is-active' : ''}`}
+                    aria-hidden=${isActive ? undefined : 'true'}
+                  >
+                    <span class="event-note-emoji">${e.emoji}</span>
+                    <span class="event-note-title">${e.title}</span>
+                    <span class="event-note-msg">${e.message}</span>
+                    ${dateLine && html`<span class="event-note-dates">${dateLine}</span>`}
+                  </div>`;
+              })}
             </div>
             ${activeEvents.length > 1 && html`
               <div class="event-note-dots">