feat(details): rebuild the message details dialog as rows

A text box could not carry a per-value context menu without parsing displayed
text back into structure, and the user did not want a text box. Each row now
holds its own value, its message index and its query, built from the parsed
message.

Every value label states Qt::PlainText. The QPlainTextEdit this replaced was
plain by design rather than by style: header values come from strangers, and a
QLabel guesses the format under AutoText.

2 files changed, 183 insertions, 0 deletions

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 68148ee..5f7bd48 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -56,3 +56,4 @@ add_qtmaildir_test(tagrules)
 add_qtmaildir_test(rulequery)
 add_qtmaildir_test(searchterm)
 add_qtmaildir_test(tagstrip)
+add_qtmaildir_test(messagedetailsdialog)
diff --git a/tests/test_messagedetailsdialog.cpp b/tests/test_messagedetailsdialog.cpp
new file mode 100644
index 0000000..4e685ce
--- /dev/null
+++ b/tests/test_messagedetailsdialog.cpp
@@ -0,0 +1,182 @@
+/*
+ * qtmaildir - a Qt6 mail client for notmuch-indexed Maildirs
+ * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <QLabel>
+#include <QSignalSpy>
+#include <QtTest>
+
+#include "htmlbuilder.h"
+#include "messagedetailsdialog.h"
+
+/// The details dialog, which shows every header of every message in a thread.
+///
+/// Rows rather than one text box since item 85, so a value can carry its own
+/// context menu without anything parsing rendered text back into structure.
+class TestMessageDetailsDialog : public QObject
+{
+    Q_OBJECT
+private slots:
+    void showsEveryHeaderOfEveryMessage();
+    void valueLabelsCannotRenderMarkup();
+    void offersASearchForEachValue();
+    void omitsAnEmptyHeader();
+    void messageIdIsShownButNotSearchable();
+
+private:
+    /// One message, with every header populated. The date's weekday matches
+    /// the date: Qt::RFC2822Date validates the two against each other, and
+    /// 2026-08-14 is a Friday.
+    ThreadRenderItem oneMessage() const
+    {
+        ThreadRenderItem item;
+        item.message.ok = true;
+        item.message.subject = QStringLiteral("Quarterly report");
+        item.message.from = QStringLiteral("Sender <sender@example.org>");
+        item.message.to = QStringLiteral("Recipient <recipient@example.org>");
+        item.message.cc = QStringLiteral("Copied <copied@example.org>");
+        item.message.date = QStringLiteral("Fri, 14 Aug 2026 09:30:00 +0200");
+        item.message.messageId = QStringLiteral("<abc123@example.org>");
+        return item;
+    }
+};
+
+void TestMessageDetailsDialog::showsEveryHeaderOfEveryMessage()
+{
+    ThreadRenderItem second = oneMessage();
+    second.message.subject = QStringLiteral("Re: Quarterly report");
+
+    MessageDetailsDialog dialog({ oneMessage(), second });
+
+    const QList<HeaderRow> rows = dialog.rows();
+    QVERIFY2(!rows.isEmpty(), "no rows: the dialog was never populated");
+
+    // Both messages are represented, each row knowing which one it belongs to.
+    QVERIFY(std::any_of(rows.cbegin(), rows.cend(), [](const HeaderRow &row) {
+        return row.messageIndex == 0;
+    }));
+    QVERIFY(std::any_of(rows.cbegin(), rows.cend(), [](const HeaderRow &row) {
+        return row.messageIndex == 1;
+    }));
+
+    QStringList values;
+    for (const HeaderRow &row : rows)
+        values << row.value;
+    QVERIFY(values.contains(QStringLiteral("Sender <sender@example.org>")));
+    QVERIFY(values.contains(QStringLiteral("Re: Quarterly report")));
+    QVERIFY(values.contains(QStringLiteral("<abc123@example.org>")));
+}
+
+void TestMessageDetailsDialog::valueLabelsCannotRenderMarkup()
+{
+    // The QPlainTextEdit this replaced was plain by DESIGN, not by style:
+    // header values come from strangers and plain text cannot interpret
+    // markup. A QLabel guesses under Qt::AutoText, so every label states its
+    // format rather than relying on escaping, which is the same protection one
+    // mistake away from failing.
+    ThreadRenderItem hostile = oneMessage();
+    hostile.message.subject =
+        QStringLiteral("<b>bold</b><img src=x onerror=1>");
+
+    MessageDetailsDialog dialog({ hostile });
+
+    const QList<QLabel *> labels = dialog.findChildren<QLabel *>();
+    QVERIFY2(!labels.isEmpty(), "no labels: the dialog was never populated");
+
+    bool sawTheSubject = false;
+    for (const QLabel *label : labels) {
+        QCOMPARE(label->textFormat(), Qt::PlainText);
+        if (label->text().contains(QStringLiteral("<b>bold</b>")))
+            sawTheSubject = true;
+    }
+
+    // The markup survives AS TEXT, which is the proof it was not interpreted.
+    QVERIFY2(sawTheSubject, "the hostile subject never reached a label");
+}
+
+void TestMessageDetailsDialog::offersASearchForEachValue()
+{
+    MessageDetailsDialog dialog({ oneMessage() });
+
+    QSignalSpy spy(&dialog, &MessageDetailsDialog::searchRequested);
+    QVERIFY(spy.isValid());
+
+    const QList<HeaderRow> rows = dialog.rows();
+    const auto from = std::find_if(
+        rows.cbegin(), rows.cend(), [](const HeaderRow &row) {
+            return row.field == QStringLiteral("from");
+        });
+    QVERIFY2(from != rows.cend(), "no From row to search from");
+    QCOMPARE(from->query, QStringLiteral("from:\"Sender <sender@example.org>\""));
+
+    // The date becomes a one-day range rather than a text match on the header.
+    const auto date = std::find_if(
+        rows.cbegin(), rows.cend(), [](const HeaderRow &row) {
+            return row.field == QStringLiteral("date");
+        });
+    QVERIFY2(date != rows.cend(), "no Date row");
+    QCOMPARE(date->query, QStringLiteral("date:2026-08-14..2026-08-14"));
+
+    // Replacing and narrowing are both offered, and the flag distinguishes them.
+    dialog.requestSearch(*from, false);
+    dialog.requestSearch(*from, true);
+    QCOMPARE(spy.count(), 2);
+    QCOMPARE(spy.at(0).at(0).toString(), from->query);
+    QCOMPARE(spy.at(0).at(1).toBool(), false);
+    QCOMPARE(spy.at(1).at(1).toBool(), true);
+}
+
+void TestMessageDetailsDialog::omitsAnEmptyHeader()
+{
+    ThreadRenderItem noCc = oneMessage();
+    noCc.message.cc.clear();
+
+    MessageDetailsDialog dialog({ noCc });
+
+    const QList<HeaderRow> rows = dialog.rows();
+    // Guard first: an absence assertion alone passes against no implementation.
+    QVERIFY2(!rows.isEmpty(), "no rows: the dialog was never populated");
+    QVERIFY(std::any_of(rows.cbegin(), rows.cend(), [](const HeaderRow &row) {
+        return row.field == QStringLiteral("from");
+    }));
+
+    for (const HeaderRow &row : rows)
+        QVERIFY(row.field != QStringLiteral("cc"));
+}
+
+void TestMessageDetailsDialog::messageIdIsShownButNotSearchable()
+{
+    // A message id names one message, and the thread holding it is already on
+    // screen, so there is nothing useful to search for. It is still shown.
+    MessageDetailsDialog dialog({ oneMessage() });
+
+    const QList<HeaderRow> rows = dialog.rows();
+    const auto id = std::find_if(
+        rows.cbegin(), rows.cend(), [](const HeaderRow &row) {
+            return row.value == QStringLiteral("<abc123@example.org>");
+        });
+    QVERIFY2(id != rows.cend(), "the message id is not shown at all");
+    QVERIFY(id->query.isEmpty());
+
+    // And asking to search it emits nothing rather than an empty query.
+    QSignalSpy spy(&dialog, &MessageDetailsDialog::searchRequested);
+    dialog.requestSearch(*id, false);
+    QCOMPARE(spy.count(), 0);
+}
+
+QTEST_MAIN(TestMessageDetailsDialog)
+#include "test_messagedetailsdialog.moc"