feat: lay out the calendar's month grid without a painter

2 files changed, 82 insertions, 0 deletions

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 6721340..bea6a31 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -76,6 +76,7 @@ add_qtmaildir_test(repeatrule)
 add_qtmaildir_test(calendarstore)
 add_qtmaildir_test(calendarwriter)
 add_qtmaildir_test(calendarsync)
+add_qtmaildir_test(monthlayout)
 add_qtmaildir_test(signatures)
 add_qtmaildir_test(busyindicator)
 add_qtmaildir_test(tagstrip)
diff --git a/tests/test_monthlayout.cpp b/tests/test_monthlayout.cpp
new file mode 100644
index 0000000..fbeb219
--- /dev/null
+++ b/tests/test_monthlayout.cpp
@@ -0,0 +1,81 @@
+/*
+ * 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 <QtTest>
+
+#include "monthlayout.h"
+
+class TestMonthLayout : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void theGridStartsOnTheLocalesFirstDay();
+    void cellsTileTheAreaWithNoGapOrOverlap();
+    void chipsThatDoNotFitBecomeMore();
+    void aPointFindsItsCell();
+};
+
+void TestMonthLayout::theGridStartsOnTheLocalesFirstDay()
+{
+    // 2026-09-01 is a Tuesday.
+    QCOMPARE(MonthLayout::gridStart(2026, 9, Qt::Monday), QDate(2026, 8, 31));
+    QCOMPARE(MonthLayout::gridStart(2026, 9, Qt::Sunday), QDate(2026, 8, 30));
+    // A month starting ON the first weekday starts on its own first day.
+    QCOMPARE(MonthLayout::gridStart(2026, 6, Qt::Monday), QDate(2026, 6, 1));
+    const MonthLayout layout(QRect(0, 0, 700, 600), 2026, 9, Qt::Monday, 20, 16);
+    QCOMPARE(layout.dateAt(0), QDate(2026, 8, 31));
+    QCOMPARE(layout.dateAt(41), QDate(2026, 10, 11));
+}
+
+void TestMonthLayout::cellsTileTheAreaWithNoGapOrOverlap()
+{
+    // 703 does not divide by 7: the remainder must go somewhere, not vanish
+    // as a gap down the right edge.
+    const QRect area(0, 0, 703, 605);
+    const MonthLayout layout(area, 2026, 9, Qt::Monday, 20, 16);
+    QCOMPARE(layout.cellRect(0).left(), area.left());
+    QCOMPARE(layout.cellRect(6).right(), area.right());
+    QCOMPARE(layout.cellRect(41).bottom(), area.bottom());
+    for (int i = 0; i < 6; ++i)
+        QCOMPARE(layout.cellRect(i).right() + 1, layout.cellRect(i + 1).left());
+    QCOMPARE(layout.cellRect(0).bottom() + 1, layout.cellRect(7).top());
+}
+
+void TestMonthLayout::chipsThatDoNotFitBecomeMore()
+{
+    // 600 / 6 rows = 100 px a cell; 20 px of day number; 16 px chips: 5 fit.
+    const MonthLayout layout(QRect(0, 0, 700, 600), 2026, 9, Qt::Monday, 20, 16);
+    QCOMPARE(layout.capacity(), 5);
+    QCOMPARE(layout.visibleChips(3), 3);
+    QCOMPARE(layout.visibleChips(5), 5);
+    // Six do not fit: four chips and a "+2 more" line in the fifth slot.
+    QCOMPARE(layout.visibleChips(6), 4);
+    QCOMPARE(layout.chipRect(0, 0).top(), layout.cellRect(0).top() + 20);
+    QVERIFY(layout.cellRect(0).contains(layout.chipRect(0, 4)));
+}
+
+void TestMonthLayout::aPointFindsItsCell()
+{
+    const MonthLayout layout(QRect(0, 0, 700, 600), 2026, 9, Qt::Monday, 20, 16);
+    QCOMPARE(layout.cellAt(layout.cellRect(17).center()), 17);
+    QCOMPARE(layout.cellAt(QPoint(-5, 10)), -1);
+}
+
+QTEST_MAIN(TestMonthLayout)
+#include "test_monthlayout.moc"