Presentation export: progress modal + inline failure log

The HTML/PDF export links were plain downloads that left the browser
silently spinning during the server-side render and, on failure, saved an
error page as pdf.txt/pdf.htm. Replace them with fetch-based downloads that
show a modal: a spinner with a 'this can take up to a minute' message while
compiling, and the actual compile log inline if the export fails. The user
can dismiss at any time; a stale request that finishes after dismissal no
longer reopens the modal. Adds the three i18n keys (en/fr + extracted).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/web/frontend/extracted-translations.json

@@ -1470,6 +1470,9 @@
   "premium_feature": "",
   "premium_plan_label": "",
   "preparing_for_export": "",
+  "preparing_your_download": "",
+  "presentation_export_can_take_a_moment": "",
+  "presentation_export_failed": "",
   "presentation_link_members": "",
   "presentation_link_private": "",
   "presentation_link_public": "",

services/web/frontend/js/features/pdf-preview/components/pdf-hybrid-download-button.tsx

@@ -1,3 +1,4 @@
+import { useCallback, useRef, useState } from 'react'
 import { useTranslation } from 'react-i18next'
 import { useDetachCompileContext as useCompileContext } from '../../../shared/context/detach-compile-context'
 import { useProjectContext } from '@/shared/context/project-context'
@@ -12,6 +13,21 @@ import {
   DropdownMenu,
   DropdownToggle,
 } from '@/shared/components/dropdown/dropdown-menu'
+import {
+  OLModal,
+  OLModalBody,
+  OLModalFooter,
+  OLModalHeader,
+  OLModalTitle,
+} from '@/shared/components/ol/ol-modal'
+import LoadingSpinner from '@/shared/components/loading-spinner'
+
+type ExportFormat = 'html' | 'pdf'
+
+function filenameFromDisposition(disposition: string | null, ext: string) {
+  const match = disposition?.match(/filename="?([^"]+)"?/)
+  return match ? match[1] : `presentation.${ext}`
+}
 
 function PdfHybridDownloadButton() {
   const { pdfDownloadUrl, pdfFile, showLogs } = useCompileContext()
@@ -19,6 +35,63 @@ function PdfHybridDownloadButton() {
   const { projectId } = useProjectContext()
   const { t } = useTranslation()
 
+  // Standalone-HTML / slide-PDF exports trigger an on-demand server-side
+  // render that can take several seconds; surface that wait (and any failure
+  // log) in a modal instead of leaving the browser silently spinning.
+  const [exporting, setExporting] = useState<ExportFormat | null>(null)
+  const [exportError, setExportError] = useState<string | null>(null)
+  // Bumped whenever the user dismisses the modal, so a request that finishes
+  // after they've closed it doesn't pop the modal back open.
+  const requestIdRef = useRef(0)
+
+  const dismiss = useCallback(() => {
+    requestIdRef.current += 1
+    setExporting(null)
+    setExportError(null)
+  }, [])
+
+  const startExport = useCallback(
+    async (format: ExportFormat) => {
+      const requestId = ++requestIdRef.current
+      setExportError(null)
+      setExporting(format)
+      try {
+        const response = await fetch(
+          `/project/${projectId}/presentation-export/${format}`,
+          { credentials: 'same-origin' }
+        )
+        if (requestId !== requestIdRef.current) return // dismissed meanwhile
+        if (!response.ok) {
+          const text = await response.text()
+          if (requestId !== requestIdRef.current) return
+          setExporting(null)
+          setExportError(text || `Export failed (HTTP ${response.status})`)
+          return
+        }
+        const blob = await response.blob()
+        if (requestId !== requestIdRef.current) return
+        const filename = filenameFromDisposition(
+          response.headers.get('Content-Disposition'),
+          format === 'pdf' ? 'pdf' : 'html'
+        )
+        const url = URL.createObjectURL(blob)
+        const link = document.createElement('a')
+        link.href = url
+        link.download = filename
+        document.body.appendChild(link)
+        link.click()
+        link.remove()
+        URL.revokeObjectURL(url)
+        setExporting(null)
+      } catch (err) {
+        if (requestId !== requestIdRef.current) return
+        setExporting(null)
+        setExportError(err instanceof Error ? err.message : String(err))
+      }
+    },
+    [projectId]
+  )
+
   if (showLogs) {
     return null
   }
@@ -30,38 +103,75 @@ function PdfHybridDownloadButton() {
 
   if (isPresentation) {
     return (
-      <Dropdown align="end">
-        <DropdownToggle
-          id="download-presentation"
-          variant="link"
-          className="pdf-toolbar-btn"
-          aria-label={t('download')}
+      <>
+        <Dropdown align="end">
+          <DropdownToggle
+            id="download-presentation"
+            variant="link"
+            className="pdf-toolbar-btn"
+            aria-label={t('download')}
+          >
+            <MaterialIcon type="download" />
+          </DropdownToggle>
+          <DropdownMenu>
+            <li role="none">
+              <DropdownItem
+                as="button"
+                onClick={() => startExport('html')}
+                disabled={exporting !== null}
+              >
+                {t('download_as_standalone_html')}
+              </DropdownItem>
+            </li>
+            <li role="none">
+              <DropdownItem
+                as="button"
+                onClick={() => startExport('pdf')}
+                disabled={exporting !== null}
+              >
+                {t('download_as_pdf_slides')}
+              </DropdownItem>
+            </li>
+          </DropdownMenu>
+        </Dropdown>
+
+        <OLModal
+          show={exporting !== null || exportError !== null}
+          onHide={dismiss}
         >
-          <MaterialIcon type="download" />
-        </DropdownToggle>
-        <DropdownMenu>
-          <li role="none">
-            <DropdownItem
-              href={`/project/${projectId}/presentation-export/html`}
-              target="_blank"
-              rel="noopener"
-              download
-            >
-              {t('download_as_standalone_html')}
-            </DropdownItem>
-          </li>
-          <li role="none">
-            <DropdownItem
-              href={`/project/${projectId}/presentation-export/pdf`}
-              target="_blank"
-              rel="noopener"
-              download
-            >
-              {t('download_as_pdf_slides')}
-            </DropdownItem>
-          </li>
-        </DropdownMenu>
-      </Dropdown>
+          <OLModalHeader closeButton>
+            <OLModalTitle>
+              {exportError
+                ? t('presentation_export_failed')
+                : t('preparing_your_download')}
+            </OLModalTitle>
+          </OLModalHeader>
+          <OLModalBody>
+            {exporting !== null ? (
+              <LoadingSpinner
+                loadingText={t('presentation_export_can_take_a_moment')}
+              />
+            ) : (
+              <pre
+                style={{
+                  whiteSpace: 'pre-wrap',
+                  wordBreak: 'break-word',
+                  maxHeight: '50vh',
+                  overflow: 'auto',
+                  marginBottom: 0,
+                }}
+              >
+                {exportError}
+              </pre>
+            )}
+          </OLModalBody>
+          <OLModalFooter>
+            <OLButton variant="secondary" onClick={dismiss}>
+              {t('close')}
+            </OLButton>
+          </OLModalFooter>
+        </OLModal>
+      </>
     )
   }
 

services/web/locales/en.json

@@ -692,6 +692,9 @@
   "download_all": "Download all",
   "download_as_pdf": "Download as PDF",
   "download_as_pdf_slides": "Download PDF slides",
+  "preparing_your_download": "Preparing your download",
+  "presentation_export_can_take_a_moment": "Compiling your presentation. This can take up to a minute for large decks…",
+  "presentation_export_failed": "Presentation export failed",
   "download_as_source_zip": "Download as source (.zip)",
   "download_as_standalone_html": "Download standalone HTML",
   "download_csv": "Download CSV",

services/web/locales/fr.json

@@ -348,6 +348,9 @@
   "dont_have_account": "Vous n’avez pas de compte ?",
   "download": "Télécharger",
   "download_as_pdf_slides": "Télécharger les diapositives PDF",
+  "preparing_your_download": "Préparation de votre téléchargement",
+  "presentation_export_can_take_a_moment": "Compilation de votre présentation. Cela peut prendre jusqu'à une minute pour les présentations volumineuses…",
+  "presentation_export_failed": "Échec de l'export de la présentation",
   "download_as_standalone_html": "Télécharger le HTML autonome",
   "download_pdf": "Télécharger le PDF",
   "download_zip_file": "Télécharger le fichier Zip",