feat: show that a tag action landed

Selecting a thread and hitting Delete changed nothing on screen, so
there was no way to tell the action had stuck.

The tag was always applied: applyTagChange() emitted dataChanged across
the row, and the Tags column did update. But Subject was set to stretch
while Tags came after it, so Subject took all free width and pushed Tags
out of view. The feedback lived in the one column that could not be seen.

Columns are now Tags, Date, From, Subject, with Subject stretching last
so nothing can be pushed off the right edge. A thread tagged deleted or
spam fills its whole row, muted red or orange with white struck-through
text, through the background, foreground and font roles, so no cue
depends on one column remaining visible.

Strike-through accompanies the fill on purpose: it survives a theme that
overrides backgrounds and reads without colour. Bold for unread still
composes with it.

Archive adds no tag, so an archived row is left unstyled for now.

1 files changed, 102 insertions, 0 deletions

diff --git a/tests/test_threadlistmodel.cpp b/tests/test_threadlistmodel.cpp
index 24ba9e2..98c477c 100644
--- a/tests/test_threadlistmodel.cpp
+++ b/tests/test_threadlistmodel.cpp
@@ -33,6 +33,11 @@ private slots:
     void reportsSubjectAndAuthors();
     void subjectShowsMessageCountOnlyForRealThreads();
     void unreadThreadsRenderBold();
+    void tagsAreTheFirstColumnAndSubjectTheLast();
+    void deletedThreadsAreRedAndStruckThrough();
+    void spamThreadsAreOrangeAndStruckThrough();
+    void doomedStylingCoversEveryColumn();
+    void ordinaryThreadsCarryNoRowColour();
     void threadIdIsReachableFromAnIndex();
     void invalidIndexesReturnNothing();
     void threadAtOutOfRangeIsSafe();
@@ -153,6 +158,103 @@ void TestThreadListModel::unreadThreadsRenderBold()
     QVERIFY(unreadFont.value<QFont>().bold());
 }
 
+void TestThreadListModel::tagsAreTheFirstColumnAndSubjectTheLast()
+{
+    // Subject stretches to fill the view, so whatever sits after it is pushed
+    // off-screen. Tags used to be there, which is why acting on a thread
+    // looked like it did nothing: the only column that changed was invisible.
+    QCOMPARE(ThreadListModel::TagsColumn, 0);
+    QCOMPARE(ThreadListModel::SubjectColumn, ThreadListModel::ColumnCount - 1);
+
+    ThreadListModel model;
+    model.appendBatch({ makeThread(QStringLiteral("t1"), QStringLiteral("hello")) });
+    QCOMPARE(model.headerData(ThreadListModel::TagsColumn, Qt::Horizontal,
+                              Qt::DisplayRole).toString(),
+             QStringLiteral("Tags"));
+    QCOMPARE(model.headerData(ThreadListModel::SubjectColumn, Qt::Horizontal,
+                              Qt::DisplayRole).toString(),
+             QStringLiteral("Subject"));
+}
+
+void TestThreadListModel::deletedThreadsAreRedAndStruckThrough()
+{
+    ThreadListModel model;
+    ThreadSummary thread = makeThread(QStringLiteral("t1"), QStringLiteral("doomed"));
+    thread.tags = QStringList{ QStringLiteral("inbox") };
+    model.appendBatch({ thread });
+
+    const QModelIndex subject = model.index(0, ThreadListModel::SubjectColumn);
+    QVERIFY(!model.data(subject, Qt::BackgroundRole).isValid());
+
+    model.applyTagChange(QStringLiteral("t1"), { QStringLiteral("deleted") }, {});
+
+    const QVariant background = model.data(subject, Qt::BackgroundRole);
+    QVERIFY(background.isValid());
+    QCOMPARE(background.value<QBrush>().color(), ThreadListModel::deletedColour());
+
+    // White text on the fill, and struck through so the state reads even in a
+    // screenshot with the colours stripped.
+    QCOMPARE(model.data(subject, Qt::ForegroundRole).value<QBrush>().color(),
+             QColor(Qt::white));
+    QVERIFY(model.data(subject, Qt::FontRole).value<QFont>().strikeOut());
+}
+
+void TestThreadListModel::spamThreadsAreOrangeAndStruckThrough()
+{
+    ThreadListModel model;
+    ThreadSummary thread = makeThread(QStringLiteral("t1"), QStringLiteral("junk"));
+    thread.tags = QStringList{ QStringLiteral("inbox") };
+    model.appendBatch({ thread });
+
+    model.applyTagChange(QStringLiteral("t1"), { QStringLiteral("spam") }, {});
+
+    const QModelIndex subject = model.index(0, ThreadListModel::SubjectColumn);
+    QCOMPARE(model.data(subject, Qt::BackgroundRole).value<QBrush>().color(),
+             ThreadListModel::spamColour());
+    QVERIFY(model.data(subject, Qt::FontRole).value<QFont>().strikeOut());
+
+    // Spam and deleted must be distinguishable, not two shades of one colour.
+    QVERIFY(ThreadListModel::spamColour() != ThreadListModel::deletedColour());
+}
+
+void TestThreadListModel::doomedStylingCoversEveryColumn()
+{
+    // A cue on one column would vanish the moment that column scrolled out of
+    // view, which is the bug this whole change exists to fix.
+    ThreadListModel model;
+    ThreadSummary thread = makeThread(QStringLiteral("t1"), QStringLiteral("doomed"));
+    thread.tags = QStringList{ QStringLiteral("inbox") };
+    model.appendBatch({ thread });
+
+    model.applyTagChange(QStringLiteral("t1"), { QStringLiteral("deleted") }, {});
+
+    for (int column = 0; column < ThreadListModel::ColumnCount; ++column) {
+        const QModelIndex index = model.index(0, column);
+        QVERIFY2(model.data(index, Qt::BackgroundRole).isValid(),
+                 qPrintable(QStringLiteral("column %1 has no background").arg(column)));
+        QVERIFY2(model.data(index, Qt::FontRole).value<QFont>().strikeOut(),
+                 qPrintable(QStringLiteral("column %1 is not struck through").arg(column)));
+    }
+}
+
+void TestThreadListModel::ordinaryThreadsCarryNoRowColour()
+{
+    // Undo has to restore the plain look, not merely drop the tag.
+    ThreadListModel model;
+    ThreadSummary thread = makeThread(QStringLiteral("t1"), QStringLiteral("normal"));
+    thread.tags = QStringList{ QStringLiteral("inbox") };
+    model.appendBatch({ thread });
+
+    model.applyTagChange(QStringLiteral("t1"), { QStringLiteral("deleted") }, {});
+    model.applyTagChange(QStringLiteral("t1"), {}, { QStringLiteral("deleted") });
+
+    const QModelIndex subject = model.index(0, ThreadListModel::SubjectColumn);
+    QVERIFY(!model.data(subject, Qt::BackgroundRole).isValid());
+    QVERIFY(!model.data(subject, Qt::ForegroundRole).isValid());
+    const QVariant font = model.data(subject, Qt::FontRole);
+    QVERIFY(!font.isValid() || !font.value<QFont>().strikeOut());
+}
+
 void TestThreadListModel::threadIdIsReachableFromAnIndex()
 {
     // The view hands MainWindow a QModelIndex; the worker needs a thread id.