Fullscreen on Safari, and a fallback where there is none

Safari on a Mac wants the webkit prefix; Safari on iOS has no fullscreen for an ordinary
element at all, only for a <video>, so requestFullscreen was simply undefined and the tab
threw. It now uses whichever spelling the browser has, and where there is none the frame
fills the viewport in-page instead — the same result minus the browser's own chrome — with
a Done button and Escape to come back. The button reads Expand rather than Fullscreen when
that is what it will do.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/KVM.tsx

@@ -22,11 +22,35 @@ import { Btn, Loading, askYes, toast, useEscape } from './ui'
 type KeyboardLock = { lock?: (keys?: string[]) => Promise<void>; unlock?: () => void }
 const keyboardAPI = (): KeyboardLock | undefined => (navigator as unknown as { keyboard?: KeyboardLock }).keyboard
 
+// Fullscreen, across the three ways browsers spell it. Safari on a Mac wants the webkit
+// prefix; Safari on iOS has no fullscreen for an ordinary element at all — only for a
+// <video> — so there the page expands inside the viewport instead, which is the same thing
+// minus the browser's own chrome.
+type FSElement = HTMLElement & { webkitRequestFullscreen?: () => Promise<void> | void }
+type FSDocument = Document & { webkitFullscreenElement?: Element | null; webkitExitFullscreen?: () => Promise<void> | void }
+const nativeFullscreen = () => {
+  if (typeof document === 'undefined') return false
+  const el = document.documentElement as FSElement
+  return typeof el.requestFullscreen === 'function' || typeof el.webkitRequestFullscreen === 'function'
+}
+const fullscreenElement = () => (document as FSDocument).fullscreenElement ?? (document as FSDocument).webkitFullscreenElement ?? null
+async function enterFullscreen(el: FSElement) {
+  if (typeof el.requestFullscreen === 'function') return el.requestFullscreen()
+  if (typeof el.webkitRequestFullscreen === 'function') return el.webkitRequestFullscreen()
+  throw new Error('this browser has no fullscreen for a page element')
+}
+function exitFullscreen() {
+  const d = document as FSDocument
+  if (typeof d.exitFullscreen === 'function') return d.exitFullscreen()
+  if (typeof d.webkitExitFullscreen === 'function') return d.webkitExitFullscreen()
+}
+
 export default function KVM({ machine, title }: { machine: string | null; title: string }) {
   const [kvm, setKvm] = useState<Device | null | undefined>(undefined)
   const [adding, setAdding] = useState(false)
   const [err, setErr] = useState('')
-  const [full, setFull] = useState(false)
+  const [full, setFull] = useState(false)   // native fullscreen is on
+  const [expanded, setExpanded] = useState(false) // the fallback: filling the viewport in-page
   const box = useRef<HTMLDivElement>(null)
   const frame = useRef<HTMLIFrameElement>(null)
   const key = machine ?? '' // the hub is a machine too, and its key is the empty one
@@ -41,21 +65,33 @@ export default function KVM({ machine, title }: { machine: string | null; title:
   // than the browser. Both are undone together when fullscreen ends, however it ends.
   useEffect(() => {
     const onChange = () => {
-      const on = !!document.fullscreenElement
+      const on = !!fullscreenElement()
       setFull(on)
       if (!on) keyboardAPI()?.unlock?.()
     }
     document.addEventListener('fullscreenchange', onChange)
-    return () => { document.removeEventListener('fullscreenchange', onChange); keyboardAPI()?.unlock?.() }
+    document.addEventListener('webkitfullscreenchange', onChange)
+    return () => {
+      document.removeEventListener('fullscreenchange', onChange)
+      document.removeEventListener('webkitfullscreenchange', onChange)
+      keyboardAPI()?.unlock?.()
+    }
   }, [])
+  // Expanding is in-page, so Escape is ours to handle.
+  useEscape(() => setExpanded(false), expanded)
 
-  const goFullscreen = async () => {
+  const goBig = async () => {
+    if (!nativeFullscreen()) { setExpanded(true); frame.current?.focus(); return }
     try {
-      await box.current?.requestFullscreen()
+      if (box.current) await enterFullscreen(box.current)
       await keyboardAPI()?.lock?.()
       frame.current?.focus()
-    } catch (e) { toast(e instanceof Error ? e.message : 'fullscreen refused', 'err') }
+    } catch {
+      setExpanded(true) // refused (an iframe policy, a permissions policy): fill the page instead
+      frame.current?.focus()
+    }
   }
+  const goSmall = () => { setExpanded(false); if (fullscreenElement()) exitFullscreen() }
 
   const remove = async () => {
     if (!kvm || !await askYes(`Forget ${title}'s KVM? The device itself is not touched — this only removes its address.`, 'Remove')) return
@@ -66,6 +102,7 @@ export default function KVM({ machine, title }: { machine: string | null; title:
   if (kvm === undefined) return <div className="dash"><Loading label="Looking…" /></div>
 
   const locks = !!keyboardAPI()?.lock
+  const big = full || expanded
 
   return (
     <div className="kvm">
@@ -76,7 +113,7 @@ export default function KVM({ machine, title }: { machine: string | null; title:
           : <span className="muted small">no KVM</span>}
         <span className="spacer" />
         {kvm && <>
-          <Btn className="btn" onClick={goFullscreen} title={locks ? 'fullscreen, and the browser stops keeping Escape, Tab and Ctrl-W for itself' : 'fullscreen — this browser will still keep some keys for itself'}>Fullscreen</Btn>
+          <Btn className="btn" onClick={goBig} title={!nativeFullscreen() ? 'fill the screen — this browser has no true fullscreen for a page element' : locks ? 'fullscreen, and the browser stops keeping Escape, Tab and Ctrl-W for itself' : 'fullscreen — this browser will still keep some keys for itself'}>{nativeFullscreen() ? 'Fullscreen' : 'Expand'}</Btn>
           <a className="btn" href={kvm.url} target="_blank" rel="noreferrer" title="the device directly, outside Ham Lab — only works on the LAN">Open ↗</a>
           <Btn className="btn" onClick={() => setAdding(true)}>Change</Btn>
           <Btn className="btn danger" onClick={remove}>Remove</Btn>
@@ -85,9 +122,10 @@ export default function KVM({ machine, title }: { machine: string | null; title:
       </div>
 
       {kvm ? (
-        <div className={'kvm-frame' + (full ? ' full' : '')} ref={box}>
+        <div className={'kvm-frame' + (full ? ' full' : '') + (expanded ? ' expanded' : '')} ref={box}>
           <iframe ref={frame} key={kvm.id} src={`/kvm/${kvm.id}/`} title={kvm.name}
             allow="fullscreen; clipboard-read; clipboard-write" />
+          {expanded && <button className="btn kvm-shrink" onClick={goSmall} title="back to the console">Done</button>}
         </div>
       ) : (
         <div className="svc-empty muted kvm-none">
@@ -98,7 +136,7 @@ export default function KVM({ machine, title }: { machine: string | null; title:
           </div>
         </div>
       )}
-      {kvm && !full && (
+      {kvm && !big && (
         <div className="kvm-hint muted small">
           Click the picture, then type — the keys go to {title}.
           {locks ? ' Fullscreen also takes Escape, Tab and Ctrl-W back from the browser.' : ' This browser keeps Escape, Tab and Ctrl-W for itself; use the device’s own on-screen keys for those, or a Chromium browser.'}