[graphics/krita] libs/global: Implement kiszug::has_value

Git commit 98ea24d9519af29c3ec3a9d7b2ae0a49dbf7631a by Dmitry Kazakov.
Committed on 07/08/2026 at 09:19.
Pushed by dkazakov into branch 'master'.

Implement kiszug::has_value

To be used when unwrapping std::optional values in the GUI

M  +3    -0    libs/global/KisZug.h
M  +1    -0    libs/global/tests/CMakeLists.txt
A  +38   -0    libs/global/tests/KisLagerTest.cpp     [License: GPL(v2.0+)]
A  +18   -0    libs/global/tests/KisLagerTest.h     [License: GPL(v2.0+)]

https://invent.kde.org/graphics/krita/-/commit/98ea24d9519af29c3ec3a9d7b2ae0a49dbf7631a

diff --git a/libs/global/KisZug.h b/libs/global/KisZug.h
index 4d37d3e0a80..840b26ceaf6 100644
--- a/libs/global/KisZug.h
+++ b/libs/global/KisZug.h
@@ -63,6 +63,9 @@ inline constexpr auto map_less_equal<qreal> = [] (qreal value) { return zug::map
 
 constexpr auto map_round = zug::map([](qreal x) -> int { return qRound(x); });
 
+// a state getter for an std::optional
+constexpr auto has_value = zug::map([](auto&& x) -> bool { return x.has_value(); });
+
 struct empty_t
 {
 };
diff --git a/libs/global/tests/CMakeLists.txt b/libs/global/tests/CMakeLists.txt
index a947485d667..a53fb39acd4 100644
--- a/libs/global/tests/CMakeLists.txt
+++ b/libs/global/tests/CMakeLists.txt
@@ -2,6 +2,7 @@ kis_add_tests(KisSignalAutoConnectionTest.cpp
     KisSignalCompressorTest.cpp
     KisForestTest.cpp
     KisMplTest.cpp
+    KisLagerTest.cpp
     KisRectsGridTest.cpp
     KisLazyStorageTest.cpp
     KisValueCacheTest.cpp
diff --git a/libs/global/tests/KisLagerTest.cpp b/libs/global/tests/KisLagerTest.cpp
new file mode 100644
index 00000000000..19f5d4ed8ab
--- /dev/null
+++ b/libs/global/tests/KisLagerTest.cpp
@@ -0,0 +1,38 @@
+/*
+ *  SPDX-FileCopyrightText: 2026 Dmitry Kazakov <[email protected]>
+ *
+ *  SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include "KisLagerTest.h"
+
+#include <simpletest.h>
+
+#include <kis_debug.h>
+
+#include <optional>
+
+#include <lager/state.hpp>
+
+#include <KisLager.h>
+#include <KisZug.h>
+
+
+void KisLagerTest::testOptionalHasValue()
+{
+    auto x = lager::state<std::optional<int>, lager::automatic_tag>{};
+    x.set(11);
+
+    // connect to the presence state
+    auto isPresentReader = lager::reader<bool>{x.xform(kiszug::has_value)};
+    auto valueReader = lager::reader<int>{x.zoom(lager::lenses::value_or(42))};
+
+    QCOMPARE(isPresentReader.get(), true);
+    QCOMPARE(valueReader.get(), 11);
+
+    x.set(std::nullopt);
+
+    QCOMPARE(isPresentReader.get(), false);
+    QCOMPARE(valueReader.get(), 42);
+}
+
+SIMPLE_TEST_MAIN(KisLagerTest)
diff --git a/libs/global/tests/KisLagerTest.h b/libs/global/tests/KisLagerTest.h
new file mode 100644
index 00000000000..e9d9342fd7c
--- /dev/null
+++ b/libs/global/tests/KisLagerTest.h
@@ -0,0 +1,18 @@
+/*
+ *  SPDX-FileCopyrightText: 2026 Dmitry Kazakov <[email protected]>
+ *
+ *  SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef KISLAGERTEST_H
+#define KISLAGERTEST_H
+
+#include <QTest>
+
+class KisLagerTest : public QObject
+{
+    Q_OBJECT
+private Q_SLOTS:
+    void testOptionalHasValue();
+};
+
+#endif // KISLAGERTEST_H