fix(editor): dismiss the selection popup when its surface leaves the viewport (#425)

The portaled position:fixed add-to-conversation button stays pinned to its
viewport anchor while the sidebar keeps every tab mounted (tab switches only
set display:none; collapsing the panel translates it off-screen), so the
popup could outlive its editor surface. Extract the popup into
useSelectionPopup and close it on any mousedown outside the button, Escape,
document hidden, window blur, and - the tab-switch/collapse path - when an
IntersectionObserver reports the editor surface off-viewport.

src/client/TextEditor.tsx

@@ -28,6 +28,7 @@ import { cmSurfaceTheme, CmThemeCompartment } from './cm-themes.ts'
 import { isDarkScheme, subscribeColorScheme } from './theme.ts'
 import { SandboxStatusBar } from './SandboxStatusBar.tsx'
 import { appendToDraft } from './conversation-draft.ts'
+import { useSelectionPopup } from './selection-popup.ts'
 import { buildSelectionInsert, linesOfSelection } from './selection-payload.ts'
 import { lazyChunkComponent } from './lazy-chunk.tsx'
 import { analyzeMarkdownHtml } from './markdown-html.ts'
@@ -41,13 +42,6 @@ import css from './sidebar.module.css'
 /** Previewable files (rendered output vs source editing). */
 type ViewMode = 'preview' | 'edit'
 
-/** The floating "add to conversation" action: payload + viewport anchor. */
-interface SelectionPopup {
-  insert: string
-  left: number
-  top: number
-}
-
 /**
  * The sandbox tokens of the HTML preview iframe. NO allow-same-origin (the
  * preview must stay in an opaque origin — with the route's own origin it
@@ -71,36 +65,23 @@ export function TextEditor(props: FileViewerProps) {
   const themeCompRef = useRef<CmThemeCompartment | null>(null)
   /** The app's resolved color scheme; the editor re-themes in place on flips. */
   const [dark, setDark] = useState(() => isDarkScheme())
-  /** The floating "add to conversation" popup (viewport-anchored; null = hidden). */
-  const [popup, setPopup] = useState<SelectionPopup | null>(null)
-  /** Live mirror of the popup state for click-time reads (no re-render race). */
-  const popupRef = useRef<SelectionPopup | null>(null)
   /** The markdown preview container (selection-containment + line lookup). */
   const mdRef = useRef<HTMLDivElement>(null)
+  const markdown = viewerId === 'markdown'
+  const html = viewerId === 'html'
 
-  const hidePopup = (): void => {
-    popupRef.current = null
-    setPopup(null)
-  }
-
-  /** Anchor the popup above the selection center; clamp inside the viewport. */
-  const showPopup = (insert: string, left: number, top: number): void => {
-    const next: SelectionPopup = {
-      insert,
-      left: Math.min(Math.max(left, 80), window.innerWidth - 80),
-      top,
-    }
-    popupRef.current = next
-    setPopup(next)
-  }
-
-  /** The popup button's click: insert the stored payload into the draft. */
-  const commitPopup = (): void => {
-    const current = popupRef.current
-    if (current === null) return
-    appendToDraft(ctx, scope.sessionId, current.insert)
-    hidePopup()
-  }
+  /**
+   * The floating "add to conversation" popup (viewport-anchored; null =
+   * hidden). The hook owns show/hide/commit plus the global dismissal
+   * listeners (outside mousedown, Escape, hidden tab/window, surface
+   * leaving the viewport) — see selection-popup.ts.
+   */
+  const selectionPopup = useSelectionPopup({
+    onCommit: (insert) => { appendToDraft(ctx, scope.sessionId, insert) },
+    // The surface that must stay on screen: the markdown preview container
+    // in preview mode, the CodeMirror host otherwise.
+    getSurface: () => (markdown && mode === 'preview' ? mdRef.current : hostRef.current),
+  })
 
   useEffect(() => subscribeColorScheme(() => { setDark(isDarkScheme()) }), [])
 
@@ -110,7 +91,7 @@ export function TextEditor(props: FileViewerProps) {
     setDraft(null)
     setDirty(false)
     setSaveState('idle')
-    hidePopup()
+    selectionPopup.hide()
   }, [content])
 
   // Create the CodeMirror editor once the content is loaded. The view owns
@@ -159,33 +140,33 @@ export function TextEditor(props: FileViewerProps) {
         ...(viewerId === 'code' || viewerId === 'markdown' ? [
           CodeMirrorView.updateListener.of((update) => {
             if (update.geometryChanged || update.viewportChanged) {
-              hidePopup()
+              selectionPopup.hide()
               return
             }
             if (!update.view.hasFocus) {
-              hidePopup()
+              selectionPopup.hide()
               return
             }
             if (!(update.selectionSet || update.docChanged || update.focusChanged)) return
             const sel = update.state.selection.main
             if (sel.empty) {
-              hidePopup()
+              selectionPopup.hide()
               return
             }
             const text = update.state.sliceDoc(sel.from, sel.to)
             if (text.trim() === '') {
-              hidePopup()
+              selectionPopup.hide()
               return
             }
             // Page coordinates (the document root may scroll); the popup is
             // position:fixed, so convert to viewport coordinates.
             const rect = update.view.coordsAtPos(sel.head)
             if (rect === null) {
-              hidePopup()
+              selectionPopup.hide()
               return
             }
             const doc = update.state.doc
-            showPopup(
+            selectionPopup.show(
               buildSelectionInsert(path, scope.cwd, {
                 start: doc.lineAt(sel.from).number,
                 end: doc.lineAt(sel.to).number,
@@ -222,7 +203,7 @@ export function TextEditor(props: FileViewerProps) {
   // it becomes visible again (CodeMirror sizes itself on reveal). A mode
   // flip also invalidates any anchored selection popup.
   useEffect(() => {
-    hidePopup()
+    selectionPopup.hide()
     if (mode === 'edit') viewRef.current?.requestMeasure()
   }, [mode])
 
@@ -242,8 +223,6 @@ export function TextEditor(props: FileViewerProps) {
     })
   }
 
-  const markdown = viewerId === 'markdown'
-  const html = viewerId === 'html'
   /** The markdown source the preview renders (draft wins over saved content). */
   const mdText = draft ?? content ?? ''
   /** The preview source: `mdText` with local image destinations rewritten to
@@ -295,22 +274,22 @@ export function TextEditor(props: FileViewerProps) {
   const handlePreviewMouseUp = (): void => {
     const sel = window.getSelection()
     if (sel === null || sel.isCollapsed || sel.anchorNode === null || sel.focusNode === null) {
-      hidePopup()
+      selectionPopup.hide()
       return
     }
     const host = mdRef.current
     if (host === null || !host.contains(sel.anchorNode) || !host.contains(sel.focusNode)) {
-      hidePopup()
+      selectionPopup.hide()
       return
     }
     const text = sel.toString()
     if (text.trim() === '') {
-      hidePopup()
+      selectionPopup.hide()
       return
     }
     const rect = sel.getRangeAt(0).getBoundingClientRect()
     const lines = linesOfSelection(mdText, text)
-    showPopup(
+    selectionPopup.show(
       buildSelectionInsert(path, scope.cwd, lines ?? undefined, text),
       rect.left + rect.width / 2,
       rect.top,
@@ -401,7 +380,7 @@ export function TextEditor(props: FileViewerProps) {
           className={css.editorMd}
           ref={mdRef}
           onMouseUp={handlePreviewMouseUp}
-          onScroll={hidePopup}
+          onScroll={selectionPopup.hide}
         >
           {/* The fence copy-button labels must come from this plugin's own
               dictionary: the DSH MarkdownText/CodeBlock are cordis-free and
@@ -449,15 +428,16 @@ export function TextEditor(props: FileViewerProps) {
           />
         </>
       )}
-      {popup !== null && createPortal(
+      {selectionPopup.popup !== null && createPortal(
         <button
           type="button"
+          ref={selectionPopup.buttonRef}
           className={css.selectionPopup}
-          style={{ left: popup.left, top: popup.top }}
+          style={{ left: selectionPopup.popup.left, top: selectionPopup.popup.top }}
           // Keep the selection (and CodeMirror focus) alive until the click
           // commits — without this the popup unmounts before click lands.
           onMouseDown={(event) => { event.preventDefault() }}
-          onClick={commitPopup}
+          onClick={selectionPopup.commit}
         >
           {t('addToConversation')}
         </button>,

src/client/selection-popup.ts

@@ -0,0 +1,157 @@
+/**
+ * The floating "add selection to conversation" popup shared by the text
+ * viewers (markdown preview + the catch-all code viewer): a viewport-anchored
+ * button portaled to `document.body`, kept alive across the selection gesture
+ * and committed on click.
+ *
+ * Dismissal contract (fixes upstream issue #425): the popup must never
+ * outlive its editor surface. The sidebar keeps every tab MOUNTED — switching
+ * tabs only flips the pane cell to `display:none` and collapsing the panel
+ * translates it off-screen — while the portaled `position:fixed` button stays
+ * pinned to its viewport anchor, ignoring both. The caller already hides on
+ * surface scrolls, selection collapse and mode flips; this hook adds the
+ * global dismissal that covers everything else:
+ *
+ * - any `mousedown` outside the button (tab bar, composer, another pane,
+ *   the collapse toggle, …) closes it;
+ * - `Escape` closes it;
+ * - the document going hidden (`visibilitychange`) or the window losing
+ *   focus closes it;
+ * - an `IntersectionObserver` on the editor surface closes it as soon as the
+ *   surface leaves the viewport — the tab-switch (`display:none`) and
+ *   panel-collapse (translated off-screen) paths have no DOM events of their
+ *   own, so the geometry signal is the only reliable one.
+ *
+ * The button's own `mousedown` is never treated as an outside click: the
+ * caller preventDefaults it to keep the selection/caret alive until the
+ * click commits (the hook's capture-phase listener runs first and must not
+ * hide for it).
+ */
+import { useEffect, useRef, useState, type RefObject } from 'react'
+
+/** The floating "add to conversation" action: payload + viewport anchor. */
+export interface SelectionPopup {
+  insert: string
+  left: number
+  top: number
+}
+
+export interface SelectionPopupOptions {
+  /** Commit the payload into the composer draft (button click). */
+  onCommit(insert: string): void
+  /**
+   * The DOM surface that must stay on screen for the popup to live: the
+   * markdown preview container in preview mode, the CodeMirror host
+   * otherwise. Called lazily (refs are null until the content loads).
+   */
+  getSurface(): HTMLElement | null
+}
+
+export interface SelectionPopupControls {
+  /** The current popup (null = hidden). */
+  popup: SelectionPopup | null
+  /** Attach to the portaled button element. */
+  buttonRef: RefObject<HTMLButtonElement>
+  /** Anchor the popup above a selection (viewport-clamped). */
+  show(insert: string, left: number, top: number): void
+  /** Hide the popup (idempotent). */
+  hide(): void
+  /** The button's click: commit the stored payload, then hide. */
+  commit(): void
+}
+
+export function useSelectionPopup(options: SelectionPopupOptions): SelectionPopupControls {
+  // Latest-callback refs: the dismissal listeners live for the mount's
+  // lifetime, so they must not capture stale closures across renders.
+  const onCommitRef = useRef(options.onCommit)
+  const getSurfaceRef = useRef(options.getSurface)
+  onCommitRef.current = options.onCommit
+  getSurfaceRef.current = options.getSurface
+
+  const [popup, setPopup] = useState<SelectionPopup | null>(null)
+  /** Live mirror for click/event-time reads (no re-render race). */
+  const popupRef = useRef<SelectionPopup | null>(null)
+  /** The portaled button itself (for the outside-click guard). */
+  const buttonRef = useRef<HTMLButtonElement>(null)
+  /** The surface visibility observer (created lazily on open). */
+  const observerRef = useRef<IntersectionObserver | null>(null)
+
+  const show = (insert: string, left: number, top: number): void => {
+    const next: SelectionPopup = {
+      insert,
+      left: Math.min(Math.max(left, 80), window.innerWidth - 80),
+      top,
+    }
+    popupRef.current = next
+    setPopup(next)
+  }
+
+  const hide = (): void => {
+    popupRef.current = null
+    setPopup(null)
+  }
+
+  const commit = (): void => {
+    const current = popupRef.current
+    if (current === null) return
+    onCommitRef.current(current.insert)
+    hide()
+  }
+
+  // Global dismissal listeners, registered once; every handler reads the
+  // live popup ref so it no-ops while no popup is open.
+  useEffect(() => {
+    const onMouseDown = (event: MouseEvent): void => {
+      if (popupRef.current === null) return
+      const button = buttonRef.current
+      if (button !== null && (button === event.target || button.contains(event.target as Node))) return
+      hide()
+    }
+    const onKeyDown = (event: KeyboardEvent): void => {
+      if (event.key === 'Escape' && popupRef.current !== null) hide()
+    }
+    const onVisibilityChange = (): void => {
+      if (document.hidden && popupRef.current !== null) hide()
+    }
+    const onWindowBlur = (): void => {
+      if (popupRef.current !== null) hide()
+    }
+    document.addEventListener('mousedown', onMouseDown, true)
+    document.addEventListener('keydown', onKeyDown, true)
+    document.addEventListener('visibilitychange', onVisibilityChange)
+    window.addEventListener('blur', onWindowBlur)
+    return () => {
+      document.removeEventListener('mousedown', onMouseDown, true)
+      document.removeEventListener('keydown', onKeyDown, true)
+      document.removeEventListener('visibilitychange', onVisibilityChange)
+      window.removeEventListener('blur', onWindowBlur)
+      observerRef.current?.disconnect()
+      observerRef.current = null
+    }
+  }, [])
+
+  // Re-target the visibility observer whenever a popup opens: the surface
+  // refs may have been null at mount (content loads async, mode flips swap
+  // the preview container for the CodeMirror host), so the surface is only
+  // trustworthy at open time.
+  useEffect(() => {
+    if (popup === null) return
+    observerRef.current?.disconnect()
+    observerRef.current = null
+    if (typeof IntersectionObserver === 'undefined') return
+    const surface = getSurfaceRef.current()
+    if (surface === null) return
+    const observer = new IntersectionObserver((entries) => {
+      for (const entry of entries) {
+        if (!entry.isIntersecting) hide()
+      }
+    }, { threshold: 0 })
+    observerRef.current = observer
+    observer.observe(surface)
+    // eslint-disable-next-line react-hooks/exhaustive-deps -- the boolean
+    // flip is the only thing that must re-run this; an anchor move while
+    // open keeps the same surface.
+  }, [popup !== null])
+
+  return { popup, buttonRef, show, hide, commit }
+}

tests/selection-popup.spec.tsx

@@ -0,0 +1,190 @@
+/**
+ * useSelectionPopup spec — the "add to conversation" popup's global dismissal
+ * contract (upstream issue #425 ①). The portaled fixed button must hide on an
+ * outside mousedown, on Escape, when the document goes hidden, when the
+ * window loses focus, and as soon as the editor surface leaves the viewport
+ * (the geometry signal behind tab switches and panel collapse) — yet it must
+ * survive a mousedown ON the button so the click can still commit the
+ * selection.
+ */
+// @vitest-environment jsdom
+import { afterEach, beforeEach, describe, expect, it } from 'vitest'
+import { createElement, useRef } from 'react'
+import { createPortal } from 'react-dom'
+import { createRoot } from 'react-dom/client'
+import { act } from 'react-dom/test-utils'
+import { useSelectionPopup } from '../src/client/selection-popup.ts'
+
+// The act() environment flag (React 18.2 reads it before flushing effects).
+;(globalThis as Record<string, unknown>).IS_REACT_ACT_ENVIRONMENT = true
+
+/** jsdom ships no IntersectionObserver; a controllable stand-in. */
+class FakeIntersectionObserver implements IntersectionObserver {
+  static last: FakeIntersectionObserver | null = null
+  readonly root: Element | Document | null = null
+  readonly rootMargin = '0px'
+  readonly thresholds: readonly number[] = [0]
+  readonly targets = new Set<Element>()
+  constructor(readonly callback: IntersectionObserverCallback) {
+    FakeIntersectionObserver.last = this
+  }
+  observe(target: Element): void { this.targets.add(target) }
+  unobserve(target: Element): void { this.targets.delete(target) }
+  disconnect(): void { this.targets.clear() }
+  takeRecords(): IntersectionObserverEntry[] { return [] }
+  /** Test hook: report that every observed target is (or is not) intersecting. */
+  fire(intersecting: boolean): void {
+    this.callback([{ isIntersecting: intersecting } as IntersectionObserverEntry], this)
+  }
+}
+
+interface HarnessCtl {
+  show(insert: string): void
+  button(): HTMLButtonElement | null
+}
+
+let ctl: HarnessCtl
+
+/** The popup consumer's rendering shape: the hook + a portaled button. */
+function Harness(props: { onCommit: (insert: string) => void }) {
+  const surfaceRef = useRef<HTMLDivElement | null>(null)
+  const surface = useSelectionPopup({
+    onCommit: props.onCommit,
+    getSurface: () => surfaceRef.current,
+  })
+  ctl = {
+    show: (insert: string) => act(() => { surface.show(insert, 100, 100) }),
+    button: () => document.querySelector<HTMLButtonElement>('[data-popup]'),
+  }
+  return createElement('div', null,
+    createElement('div', { ref: surfaceRef, 'data-surface': true }),
+    surface.popup === null ? null : createPortal(
+      createElement('button', {
+        type: 'button',
+        ref: surface.buttonRef,
+        'data-popup': true,
+        onClick: surface.commit,
+      }, surface.popup.insert),
+      document.body,
+    ),
+  )
+}
+
+let container: HTMLDivElement
+let root: ReturnType<typeof createRoot>
+let commitCalls: string[]
+
+function mount(): void {
+  container = document.createElement('div')
+  document.body.append(container)
+  root = createRoot(container)
+  commitCalls = []
+  act(() => {
+    root.render(createElement(Harness, { onCommit: (insert: string) => { commitCalls.push(insert) } }))
+  })
+}
+
+function unmount(): void {
+  act(() => { root.unmount() })
+  container.remove()
+}
+
+const RealIntersectionObserver = globalThis.IntersectionObserver
+
+beforeEach(() => {
+  ;(globalThis as { IntersectionObserver: unknown }).IntersectionObserver = FakeIntersectionObserver
+  FakeIntersectionObserver.last = null
+})
+
+afterEach(() => {
+  ;(globalThis as { IntersectionObserver: unknown }).IntersectionObserver = RealIntersectionObserver
+  document.body.innerHTML = ''
+})
+
+describe('useSelectionPopup', () => {
+  it('shows the popup button with the payload', () => {
+    mount()
+    ctl.show('PAYLOAD')
+    const button = ctl.button()
+    expect(button).not.toBeNull()
+    expect(button?.textContent).toBe('PAYLOAD')
+    unmount()
+  })
+
+  it('commits the payload on click, then hides', () => {
+    mount()
+    ctl.show('PAYLOAD')
+    const button = ctl.button()!
+    act(() => { button.dispatchEvent(new MouseEvent('click', { bubbles: true })) })
+    expect(commitCalls).toEqual(['PAYLOAD'])
+    expect(ctl.button()).toBeNull()
+    unmount()
+  })
+
+  it('hides on a mousedown outside the button', () => {
+    mount()
+    ctl.show('PAYLOAD')
+    const elsewhere = document.createElement('div')
+    document.body.append(elsewhere)
+    act(() => { elsewhere.dispatchEvent(new MouseEvent('mousedown', { bubbles: true })) })
+    expect(ctl.button()).toBeNull()
+    unmount()
+  })
+
+  it('survives a mousedown ON the button so the click can commit', () => {
+    mount()
+    ctl.show('PAYLOAD')
+    const button = ctl.button()!
+    act(() => { button.dispatchEvent(new MouseEvent('mousedown', { bubbles: true })) })
+    expect(ctl.button()).not.toBeNull()
+    unmount()
+  })
+
+  it('hides on Escape', () => {
+    mount()
+    ctl.show('PAYLOAD')
+    act(() => { document.dispatchEvent(new KeyboardEvent('keydown', { key: 'Escape' })) })
+    expect(ctl.button()).toBeNull()
+    unmount()
+  })
+
+  it('hides when the document goes hidden (browser tab switched away)', () => {
+    mount()
+    ctl.show('PAYLOAD')
+    const prototypeDescriptor = Object.getOwnPropertyDescriptor(Document.prototype, 'hidden')
+    Object.defineProperty(document, 'hidden', { value: true, configurable: true })
+    try {
+      act(() => { document.dispatchEvent(new Event('visibilitychange')) })
+      expect(ctl.button()).toBeNull()
+    } finally {
+      if (prototypeDescriptor !== undefined) Object.defineProperty(document, 'hidden', prototypeDescriptor)
+      else delete (document as { hidden?: boolean }).hidden
+    }
+    unmount()
+  })
+
+  it('hides when the window loses focus', () => {
+    mount()
+    ctl.show('PAYLOAD')
+    act(() => { window.dispatchEvent(new Event('blur')) })
+    expect(ctl.button()).toBeNull()
+    unmount()
+  })
+
+  it('watches the editor surface: off-viewport (tab switch / collapse) hides, on-viewport keeps', () => {
+    mount()
+    ctl.show('PAYLOAD')
+    const observer = FakeIntersectionObserver.last
+    expect(observer).not.toBeNull()
+    expect(observer!.targets.size).toBe(1)
+    // The observed target is the hook's surface element.
+    expect([...observer!.targets][0]?.getAttribute('data-surface')).toBe('true')
+    // Surfaced on screen (or display:none removed): the popup stays.
+    act(() => { observer!.fire(true) })
+    expect(ctl.button()).not.toBeNull()
+    // Hidden / translated off-screen: the popup must not survive it.
+    act(() => { observer!.fire(false) })
+    expect(ctl.button()).toBeNull()
+    unmount()
+  })
+})