feat(search): search for the selected body text

selectedText() reads the selection with no script injection; JavaScript stays
disabled in the profile. The page's standard menu is kept and the entries are
added to it below a separator.

The quoting is tested through a function taking the text, so it needs no live
web engine: a selection is arbitrary prose and can carry quotes, newlines and
query syntax, none of which notmuch reports as an error.

3 files changed, 88 insertions, 0 deletions

diff --git a/src/messageview.cpp b/src/messageview.cpp
index 8a1976d..5f7c9d2 100644
--- a/src/messageview.cpp
+++ b/src/messageview.cpp
@@ -153,6 +153,12 @@ MessageView::MessageView(QWidget *parent)
     settings->setAttribute(QWebEngineSettings::PluginsEnabled, false);
     settings->setAttribute(QWebEngineSettings::FullScreenSupportEnabled, false);
 
+    // Item 85: a selection in the body is searchable. CustomContextMenu so the
+    // page's standard entries survive and the search is added to them.
+    m_view->setContextMenuPolicy(Qt::CustomContextMenu);
+    connect(m_view, &QWidget::customContextMenuRequested,
+            this, &MessageView::showBodyContextMenu);
+
     // Ctrl+wheel zoom. The filter goes on the application rather than on
     // m_view: the wheel event is delivered to an internal QQuickWidget the
     // view creates lazily, so there is no child to filter at this point and a
@@ -569,6 +575,42 @@ void MessageView::showHeaderContextMenu(const QPoint &pos)
     menu.exec(m_headerLabel->mapToGlobal(pos));
 }
 
+SearchOffer MessageView::selectionSearchOffer(const QString &selectedText) const
+{
+    const QString query = SearchTerm::quote(selectedText);
+    if (query.isEmpty())
+        return {};
+
+    constexpr int kMaxLabel = 40;
+    const QString shown = selectedText.simplified();
+    return { shown.size() > kMaxLabel
+                 ? shown.left(kMaxLabel) + QStringLiteral("...")
+                 : shown,
+             query };
+}
+
+void MessageView::showBodyContextMenu(const QPoint &pos)
+{
+    // The page's own menu first: copy, select all and the rest stay exactly as
+    // they were. This adds to that menu rather than replacing it.
+    QMenu *menu = m_view->createStandardContextMenu();
+    if (!menu)
+        menu = new QMenu(this);
+    menu->setAttribute(Qt::WA_DeleteOnClose);
+
+    // selectedText() reads the selection out of the render process with no
+    // script injection. JavaScript is disabled in this profile and stays so.
+    const SearchOffer offer = selectionSearchOffer(m_view->page()->selectedText());
+    if (!offer.query.isEmpty()) {
+        menu->addSeparator();
+        addSearchEntries(menu, { offer });
+    }
+
+    // popup() rather than exec(): the menu owns itself via WA_DeleteOnClose and
+    // must not block this handler.
+    menu->popup(m_view->mapToGlobal(pos));
+}
+
 void MessageView::showDetailsDialog()
 {
     if (m_items.isEmpty())
diff --git a/src/messageview.h b/src/messageview.h
index 26ed216..3e600f0 100644
--- a/src/messageview.h
+++ b/src/messageview.h
@@ -140,6 +140,15 @@ public:
     /// parsing it back: rich text does not survive a second parse.
     QList<SearchOffer> headerSearchOffers() const { return m_headerOffers; }
 
+    /// The offer for a body selection, its query empty when there is nothing
+    /// usable selected.
+    ///
+    /// Takes the text rather than reading the page, so the quoting is testable
+    /// without a live web engine and a rendered document. A selection is
+    /// arbitrary prose and can carry quotes, newlines and query syntax, none
+    /// of which notmuch reports as an error.
+    SearchOffer selectionSearchOffer(const QString &selectedText) const;
+
 public slots:
     void toggleHtml();
     void loadRemoteContent();
@@ -235,6 +244,9 @@ private:
     /// Builds and pops the header's menu at `pos`, in the label's coordinates.
     void showHeaderContextMenu(const QPoint &pos);
 
+    /// Builds and pops the web view's menu, keeping its standard entries.
+    void showBodyContextMenu(const QPoint &pos);
+
     /// Appends a "Search for ..." submenu per offer, each holding the replace
     /// and the narrow operation.
     ///
diff --git a/tests/test_messageview.cpp b/tests/test_messageview.cpp
index 6403308..f83a377 100644
--- a/tests/test_messageview.cpp
+++ b/tests/test_messageview.cpp
@@ -52,6 +52,7 @@ private slots:
     void headerOffersSubjectDateAndSenderForOneMessage();
     void headerOffersNoSenderForARealThread();
     void headerOffersNothingForAnAbsentField();
+    void bodySelectionBecomesAQuotedSearch();
 
 private:
     QWebEngineView *webViewOf(MessageView *view) const
@@ -663,5 +664,38 @@ void TestMessageView::headerOffersNothingForAnAbsentField()
         QVERIFY(!query.startsWith(QStringLiteral("cc:")));
 }
 
+void TestMessageView::bodySelectionBecomesAQuotedSearch()
+{
+    // The selection reaches the query as ONE quoted term. Asserted on the
+    // constructed string: a query that lost its quoting is not an error to
+    // notmuch, it simply matches nothing, so nothing downstream would report
+    // this being wrong.
+    //
+    // Takes the text as an argument rather than reading the page, so the
+    // quoting is testable without a live web engine and a rendered document.
+    MessageView view;
+
+    QCOMPARE(view.selectionSearchOffer(QStringLiteral("invoice 4471")).query,
+             QStringLiteral("\"invoice 4471\""));
+
+    // A selection spanning paragraphs arrives full of newlines.
+    QCOMPARE(view.selectionSearchOffer(
+                 QStringLiteral("first line\n\nsecond line")).query,
+             QStringLiteral("\"first line second line\""));
+
+    // Query syntax in the selection is data, not syntax: it is quoted, not
+    // interpreted, so a selection reading "a or b" searches for that phrase.
+    QCOMPARE(view.selectionSearchOffer(QStringLiteral("tag:inbox or x")).query,
+             QStringLiteral("\"tag:inbox or x\""));
+
+    // Nothing selected means no entry, rather than an entry searching for "".
+    QVERIFY(view.selectionSearchOffer(QString()).query.isEmpty());
+    QVERIFY(view.selectionSearchOffer(QStringLiteral("  \n ")).query.isEmpty());
+
+    // A usable offer always carries a label for the menu to show.
+    QVERIFY(!view.selectionSearchOffer(QStringLiteral("invoice 4471"))
+                 .label.isEmpty());
+}
+
 QTEST_MAIN(TestMessageView)
 #include "test_messageview.moc"