--- a/libgui/src/documentation.cc	Thu Nov 05 18:43:39 2020 -0500
+++ b/libgui/src/documentation.cc	Thu Nov 05 16:50:55 2020 -0800
@@ -36,8 +36,8 @@
 #include <QFileInfo>
 #include <QHelpContentWidget>
 #include <QHelpIndexWidget>
-#if defined (HAVE_QHELPLINK)
-#include <QHelpLink>
+#if defined (HAVE_NEW_QHELPINDEXWIDGET_API)
+#  include <QHelpLink>
 #endif
 #include <QHelpSearchEngine>
 #include <QHelpSearchQueryWidget>
@@ -185,8 +185,8 @@
 
     if (m_help_engine)
       {
-#if defined (HAVE_QHELPLINK)
-        // Help engine uses filters instead of old api since Qt 5.15
+#if defined (HAVE_NEW_QHELPINDEXWIDGET_API)
+        // Starting in Qt 5.15, help engine uses filters instead of old API
         m_help_engine->setUsesFilterEngine (true);
 #endif
         // Layout contents, index and search
@@ -234,16 +234,16 @@
 
         navi->addTab (index_all, tr ("Function Index"));
 
-#if defined (HAVE_QHELPLINK)
+#if defined (HAVE_NEW_QHELPINDEXWIDGET_API)
         connect (m_help_engine->indexWidget (),
                  &QHelpIndexWidget::documentActivated,
-                  this, [this](const QHelpLink &link) {
+                 this, [this](const QHelpLink &link) {
                         m_doc_browser->handle_index_clicked (link.url);});
 #else
-        connect(m_help_engine->indexWidget (),
-                SIGNAL (linkActivated (const QUrl&, const QString&)),
-                m_doc_browser, SLOT(handle_index_clicked (const QUrl&,
-                                                          const QString&)));
+        connect (m_help_engine->indexWidget (),
+                 SIGNAL (linkActivated (const QUrl&, const QString&)),
+                 m_doc_browser, SLOT(handle_index_clicked (const QUrl&,
+                                                           const QString&)));
 #endif
 
         connect (m_filter, SIGNAL (editTextChanged (const QString&)),

--- a/m4/acinclude.m4	Thu Nov 05 18:43:39 2020 -0500
+++ b/m4/acinclude.m4	Thu Nov 05 16:50:55 2020 -0800
@@ -431,15 +431,16 @@
   fi
 ])
 dnl
-dnl Check whether the structure QtHelpLink is defined. Then,
-dnl QHelpIndexWidget emits documentActivates instead of linkActivated.
-dnl This structure/signal was introduced in Qt 5.15.
+dnl Check whether new API is used with QHelpIndexWidget.
+dnl Under new API, QHelpIndexWidget emits documentActivates.
+dnl Under old API, QHelpIndexWidget emits linkActivated.
+dnl New structure/signal API was introduced in Qt 5.15.
 dnl
 dnl FIXME: Delete this entirely when we drop support for Qt 5.14 or older.
 dnl
-AC_DEFUN([OCTAVE_CHECK_FUNC_QHELPLINK], [
-  AC_CACHE_CHECK([for QHelpLink],
-    [octave_cv_func_qhelplink],
+AC_DEFUN([OCTAVE_CHECK_NEW_QHELPINDEXWIDGET_API], [
+  AC_CACHE_CHECK([for new QHelpIndexWidget API],
+    [octave_cv_new_qhelpindexwidget_api],
     [AC_LANG_PUSH(C++)
     ac_octave_save_CPPFLAGS="$CPPFLAGS"
     ac_octave_save_CXXFLAGS="$CXXFLAGS"
@@ -450,15 +451,15 @@
         ]], [[
         QHelpLink link;
         ]])],
-      octave_cv_func_qhelplink=yes,
-      octave_cv_func_qhelplink=no)
+      octave_cv_new_qhelpindexwidget_api=yes,
+      octave_cv_new_qhelpindexwidget_api=no)
     CPPFLAGS="$ac_octave_save_CPPFLAGS"
     CXXFLAGS="$ac_octave_save_CXXFLAGS"
     AC_LANG_POP(C++)
   ])
-  if test $octave_cv_func_qhelplink = yes; then
-    AC_DEFINE(HAVE_QHELPLINK, 1,
-      [Define to 1 if you have the `QHelpLink' structure.])
+  if test $octave_cv_new_qhelpindexwidget_api = yes; then
+    AC_DEFINE(HAVE_NEW_QHELPINDEXWIDGET_API, 1,
+      [Define to 1 if using new QHelpIndexWidget API.])
   fi
 ])
 dnl
@@ -1894,7 +1895,7 @@
     OCTAVE_CHECK_FUNC_QFONTMETRICS_HORIZONTAL_ADVANCE
     OCTAVE_CHECK_FUNC_QGUIAPPLICATION_SETDESKTOPFILENAME
     OCTAVE_CHECK_FUNC_QHELPSEARCHQUERYWIDGET_SEARCHINPUT
-    OCTAVE_CHECK_FUNC_QHELPLINK
+    OCTAVE_CHECK_NEW_QHELPINDEXWIDGET_API
     OCTAVE_CHECK_FUNC_QLIST_ITERATOR_CONSTRUCTOR
     OCTAVE_CHECK_FUNC_QSCREEN_DEVICEPIXELRATIO