feat: open the unsynced-changes count to see what it counts

Item 119, and item 146 which is the same request recorded again. The status
bar's count answers "is my work safe to quit on" and could not say what the
work was.

The label opens a read-only list on a click. A QLabel has no clicked signal,
so the press is taken by MainWindow's existing event filter rather than by
replacing the label with a flat QToolButton, which would have brought the
style's button metrics into a status bar the label already sits correctly
in. The pointing-hand cursor is the affordance, since a status-bar label has
room for nothing else.

The layout is the user's own: a message appears once with its actions
beneath it. PendingChangesDialog::rowsFor() does the grouping over a run of
rows sharing an id, which the snapshot has already ordered, so the actions
under one message keep the order they were made in.

Read-only, deliberately. Retrying or discarding a change from here would be
a new mutation path with its own undo question, and the count exists to be
understood rather than edited.

Three rules the tests pin, each of which is a way the list could disagree
with the count it was opened from:

- Grouping must not collapse: two actions on one message are two rows.
- A thread row stays thread-scoped and reports how many messages it covered.
- An id the index no longer holds still opens a run of its own, showing that
  its subject is unknown rather than folding its actions under the message
  above it. This is why the row carries startsMessage rather than inferring
  it from a non-empty subject.

The queued call carrying QStringList, QList<bool> and QList<int> is covered
by a test that drives it across a real thread, since a container whose
metatype does not resolve is dropped at runtime and the slot runs with a
default. Both survive on Qt 6.11; the test is what says so, and what would
fail if that changed.

Italian ships with it: five new strings, lupdate clean, lrelease 522
finished and 0 unfinished.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01P88Q3MCSCSQxKDy7pmXh9F

1 files changed, 121 insertions, 0 deletions

diff --git a/src/pendingchangesdialog.cpp b/src/pendingchangesdialog.cpp
new file mode 100644
index 0000000..71e3bb0
--- /dev/null
+++ b/src/pendingchangesdialog.cpp
@@ -0,0 +1,121 @@
+/*
+ * 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 "pendingchangesdialog.h"
+
+#include <QDialogButtonBox>
+#include <QGridLayout>
+#include <QLabel>
+#include <QScrollArea>
+#include <QVBoxLayout>
+
+QVector<PendingChangeRow> PendingChangesDialog::rowsFor(
+    const QVector<PendingChange> &changes)
+{
+    QVector<PendingChangeRow> rows;
+    rows.reserve(changes.size());
+
+    // A run is a stretch of changes sharing one id, which the snapshot has
+    // already grouped. Only the first row of a run carries a subject, so the
+    // actions read as belonging to the message above them.
+    //
+    // Compared against the PREVIOUS id rather than collected into a map: the
+    // snapshot's order is deliberate (the actions under one message keep the
+    // order they were made in), and a map would discard it.
+    QString previousId;
+    bool first = true;
+    for (const PendingChange &change : changes) {
+        const bool startsMessage = first || change.id != previousId;
+        rows.append(PendingChangeRow{
+            startsMessage ? change.subject : QString(),
+            change.action,
+            startsMessage,
+            startsMessage ? change.messageCount : -1 });
+        previousId = change.id;
+        first = false;
+    }
+    return rows;
+}
+
+PendingChangesDialog::PendingChangesDialog(
+    const QVector<PendingChange> &changes, QWidget *parent)
+    : QDialog(parent), m_rows(rowsFor(changes))
+{
+    setWindowTitle(tr("Unsynced changes"));
+
+    auto *layout = new QVBoxLayout(this);
+
+    auto *intro = new QLabel(
+        tr("Changes made here that a sync has not yet carried to the mail "
+           "store. This list is a snapshot taken when it was opened."),
+        this);
+    intro->setWordWrap(true);
+    layout->addWidget(intro);
+
+    auto *content = new QWidget;
+    auto *grid = new QGridLayout(content);
+    grid->setColumnStretch(0, 1);
+
+    int line = 0;
+    for (const PendingChangeRow &row : m_rows) {
+        if (row.startsMessage) {
+            // PlainText stated rather than left to Qt, for the reason
+            // MessageDetailsDialog states it on every value: a subject comes
+            // from a stranger, and a QLabel guesses under Qt::AutoText. Plain
+            // text cannot interpret markup, so there is nothing to escape.
+            QString text = row.subject;
+            if (text.isEmpty()) {
+                // The id no longer resolves. The row stays, because the count
+                // the user clicked has to equal the list they are shown.
+                text = tr("(no longer in the index)");
+            }
+            if (row.messageCount >= 0) {
+                text = tr("%1 (whole thread, %n message(s))", "",
+                          row.messageCount).arg(text);
+            }
+            auto *subject = new QLabel(text, content);
+            subject->setTextFormat(Qt::PlainText);
+            subject->setWordWrap(true);
+            grid->addWidget(subject, line, 0);
+        }
+
+        auto *action = new QLabel(row.action, content);
+        action->setTextFormat(Qt::PlainText);
+        grid->addWidget(action, line, 1, Qt::AlignTop | Qt::AlignRight);
+        ++line;
+    }
+
+    if (m_rows.isEmpty()) {
+        grid->addWidget(new QLabel(tr("Nothing is waiting to be synced."),
+                                   content),
+                        0, 0);
+    }
+
+    grid->setRowStretch(line, 1);
+
+    auto *scroll = new QScrollArea(this);
+    scroll->setWidget(content);
+    scroll->setWidgetResizable(true);
+    layout->addWidget(scroll);
+
+    auto *buttons = new QDialogButtonBox(QDialogButtonBox::Close, this);
+    connect(buttons, &QDialogButtonBox::rejected, this, &QDialog::reject);
+    layout->addWidget(buttons);
+
+    resize(600, 380);
+}