4 files changed, 107 insertions, 0 deletions

diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index e8b4dda..e2df6de 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -1324,6 +1324,9 @@ void MainWindow::showTagRulesDialog()
     // setFolders refills the rows that exist by then.
     QMetaObject::invokeMethod(m_worker, "requestFolders", Qt::QueuedConnection);
 
+    connect(dialog, &TagRulesDialog::previewRequested,
+            this, &MainWindow::onRulePreviewRequested);
+
     connect(dialog, &TagRulesDialog::countsRequested, this, [this, dialog]() {
         QMetaObject::invokeMethod(
             m_worker, "requestMessageCounts", Qt::QueuedConnection,
@@ -1570,6 +1573,46 @@ void MainWindow::onCountsReady(const QVector<int> &counts, quint64 generation)
         m_messageView->showPlaceholder(placeholderHelpers());
 }
 
+QString MainWindow::queryTextForTesting() const
+{
+    return m_queryEdit->text();
+}
+
+QString MainWindow::selectedAccountForTesting() const
+{
+    return m_accountBox->currentData().toString();
+}
+
+void MainWindow::selectAccountForTesting(const QString &key)
+{
+    const int index = m_accountBox->findData(key);
+    if (index >= 0)
+        m_accountBox->setCurrentIndex(index);
+}
+
+void MainWindow::onRulePreviewRequested(const QString &query)
+{
+    // Unscoped, deliberately. runQuery() wraps the bar's text in the selected
+    // account's scope, and a rule query usually names its own path already
+    // (path:"work/**" is what every account rule looks like), so previewing
+    // one with an account selected would scope it twice and match nothing.
+    // That reads as "this rule collects no mail", which is the opposite of
+    // what the preview is for.
+    m_accountBox->setCurrentIndex(0);
+
+    // Through the query bar, like onPlaceholderQueryRequested: the bar then
+    // shows what is on screen and the user can edit the rule's query there
+    // before deciding to change the rule itself.
+    m_queryEdit->setText(query);
+    runCurrentQuery();
+
+    // The dialog is a separate window and may be covering this one or sitting
+    // beside it. Raising makes the result visible either way, and the dialog
+    // stays open so the two can be compared.
+    raise();
+    activateWindow();
+}
+
 void MainWindow::onPlaceholderQueryRequested(const QString &query)
 {
     // Through the query bar rather than straight to the worker, so the bar
diff --git a/src/mainwindow.h b/src/mainwindow.h
index adf63b0..18fbbb4 100644
--- a/src/mainwindow.h
+++ b/src/mainwindow.h
@@ -185,6 +185,27 @@ public:
     /// The generation the next counts reply must carry to be accepted.
     quint64 countsGenerationForTesting() const { return m_countsGeneration; }
 
+    /// The query bar's text, and the account the selector is scoped to
+    /// (empty for "All accounts"). Both are what a rule preview writes: the
+    /// bar so the user can see and edit what ran, and the selector because
+    /// runQuery() wraps the text in the selected account's scope, which would
+    /// double-scope a rule query that already names its own path.
+    QString queryTextForTesting() const;
+    QString selectedAccountForTesting() const;
+
+    /// Scopes the view to one account, as choosing it in the selector does.
+    /// A test for the rule preview needs this: with no account selected the
+    /// box already sits at "All accounts", so asserting that a preview leaves
+    /// it there passes whether or not the preview clears it.
+    void selectAccountForTesting(const QString &key);
+
+    /// Runs a rule preview without the dialog, which the offscreen platform
+    /// cannot click a button in.
+    void previewRuleQueryForTesting(const QString &query)
+    {
+        onRulePreviewRequested(query);
+    }
+
 protected:
     void closeEvent(QCloseEvent *event) override;
 
@@ -293,6 +314,11 @@ private slots:
     /// Runs a query the user clicked on the placeholder pane.
     void onPlaceholderQueryRequested(const QString &query);
 
+    /// Runs one tagging rule's query in the thread list, so the user can see
+    /// which mail it collects. The rules dialog stays open; the point is to
+    /// compare the rule against its results.
+    void onRulePreviewRequested(const QString &query);
+
     /// Opens the auto-tagging rules editor, or raises the one already open.
     void showTagRulesDialog();
 
diff --git a/src/tagrulesdialog.cpp b/src/tagrulesdialog.cpp
index 285043a..4fca971 100644
--- a/src/tagrulesdialog.cpp
+++ b/src/tagrulesdialog.cpp
@@ -234,6 +234,11 @@ TagRulesDialog::TagRulesDialog(QWidget *parent)
     buttons->addWidget(copyButton);
     buttons->addWidget(deleteButton);
     buttons->addStretch();
+    m_previewButton = new QPushButton(tr("&Preview in list"), this);
+    m_previewButton->setToolTip(
+        tr("Run this rule's query in the main window, to see which mail it "
+           "collects. This does not tag anything."));
+    buttons->addWidget(m_previewButton);
     buttons->addWidget(refreshButton);
     layout->addLayout(buttons);
 
@@ -251,6 +256,8 @@ TagRulesDialog::TagRulesDialog(QWidget *parent)
             this, &TagRulesDialog::onCopyRule);
     connect(deleteButton, &QPushButton::clicked,
             this, &TagRulesDialog::onDeleteRule);
+    connect(m_previewButton, &QPushButton::clicked,
+            this, &TagRulesDialog::previewForTest);
     connect(refreshButton, &QPushButton::clicked,
             this, &TagRulesDialog::countsRequested);
     connect(box, &QDialogButtonBox::accepted,
@@ -369,6 +376,23 @@ int TagRulesDialog::heightDemandedBelowListForTest() const
     return m_splitter->widget(1)->minimumSizeHint().height();
 }
 
+void TagRulesDialog::previewForTest()
+{
+    // Flush any half-typed edit first, so previewing shows what the rule
+    // says NOW rather than what it said when the row was selected.
+    applyEditsToCurrentRule();
+
+    const int index = currentIndex();
+    if (index < 0 || index >= m_working.size())
+        return;
+
+    const QString query = m_working.at(index).query;
+    if (query.isEmpty())
+        return;
+
+    emit previewRequested(query);
+}
+
 int TagRulesDialog::conditionAreaHeightForTest() const
 {
     // The CAP itself, not a qMin against the scroll area's own size hint: a
diff --git a/src/tagrulesdialog.h b/src/tagrulesdialog.h
index de35a55..e8979fe 100644
--- a/src/tagrulesdialog.h
+++ b/src/tagrulesdialog.h
@@ -109,6 +109,10 @@ public:
     /// the width the user had dragged.
     void reloadListForTest();
 
+    /// Presses Preview, which is otherwise reachable only through a click on
+    /// a button whose geometry the offscreen platform does not guarantee.
+    void previewForTest();
+
     /// The height the condition-row editor asks for. This is what squeezed
     /// the rule list: a stretch factor only shares out space ABOVE each
     /// widget's minimum, so every row added here came out of the list.
@@ -133,6 +137,15 @@ signals:
     /// Asks the owner to run countQueries() through the worker.
     void countsRequested();
 
+    /// Asks the owner to run one rule's query in the main window, so the user
+    /// can see WHICH mail a rule collects rather than how much.
+    ///
+    /// The query goes out exactly as stored: no `tag:new`, and no wrapping
+    /// parentheses. The post-new hook adds both when it applies a rule, and a
+    /// preview that copied them would match nothing outside a sync window,
+    /// since `tag:new` is set only on mail that has just arrived.
+    void previewRequested(const QString &query);
+
 public slots:
     /// Corpus counts, positionally paired with countQueries().
     void setCounts(const QVector<int> &counts);
@@ -241,6 +254,7 @@ private:
     /// still squeezed, because a stretch factor only shares out space above
     /// each widget's minimum and the form's grew with every condition row.
     QSplitter *m_splitter = nullptr;
+    QPushButton *m_previewButton = nullptr;
     QVBoxLayout *m_rowsLayout = nullptr;
     QVBoxLayout *m_exclusionsLayout = nullptr;
     QLabel *m_exclusionsHeader = nullptr;