Add KWindowStateSaver

This is basically the C++ counter-part to
https://invent.kde.org/frameworks/kconfig/-/merge_requests/94
and allows to easily retrofit window size persistence on existing windows/
dialogs, replacing e.g. code like
https://invent.kde.org/pim/pimcommon/-/blob/master/src/pimcommon/widgets/kpimprintpreviewdialog.cpp.

This is a bit more complicated than one might expect, as KWindowConfig
works with QWindows, but that's something freshly created QWidget windows/
dialogs don't have yet. Additionally, we are in a library here that doesn't
depend on Qt::Widgets. To overcome this we move the widget-dependent code
(basically just a call to QWidget::windowHandle()) to inline template code
(and thus into the consumer), use std::function's type erasure to pass it
into the library code, and an event filter on the widget to wait for the
QWindow to become available.

2 files changed, 95 insertions, 0 deletions

diff --git a/autotests/CMakeLists.txt b/autotests/CMakeLists.txt
index 7b5a73b1..458f8f97 100644
--- a/autotests/CMakeLists.txt
+++ b/autotests/CMakeLists.txt
@@ -82,3 +82,8 @@ if (NOT CMAKE_CROSSCOMPILING)
     add_subdirectory(kconfig_compiler)
 endif()
 endif()
+
+find_package(Qt${QT_MAJOR_VERSION} OPTIONAL_COMPONENTS Widgets)
+if (TARGET Qt${QT_MAJOR_VERSION}::Widgets)
+    ecm_add_test(kwindowstatesavertest.cpp LINK_LIBRARIES KF5::ConfigGui Qt${QT_MAJOR_VERSION}::Test Qt${QT_MAJOR_VERSION}::Widgets)
+endif()
diff --git a/autotests/kwindowstatesavertest.cpp b/autotests/kwindowstatesavertest.cpp
new file mode 100644
index 00000000..a8b67218
--- /dev/null
+++ b/autotests/kwindowstatesavertest.cpp
@@ -0,0 +1,90 @@
+/*
+    SPDX-FileCopyrightText: 2022 Volker Krause <vkrause@kde.org>
+    SPDX-License-Identifier: LGPL-2.0-or-later
+*/
+
+#include "kwindowstatesaver.h"
+#include "kconfiggroup.h"
+#include "ksharedconfig.h"
+
+#include <QSignalSpy>
+#include <QStandardPaths>
+#include <QTest>
+
+#include <QFontDialog>
+
+class KWindowStateSaverTest : public QObject
+{
+    Q_OBJECT
+private Q_SLOTS:
+    void initTestCase();
+    void testTopLevelDialog();
+    void testSubDialog();
+};
+
+void KWindowStateSaverTest::initTestCase()
+{
+    QStandardPaths::setTestModeEnabled(true);
+}
+
+void KWindowStateSaverTest::testTopLevelDialog()
+{
+    auto cfg = KSharedConfig::openStateConfig();
+    cfg->deleteGroup("topLevelDialogTest");
+    QSize dlgSize(720, 720);
+
+    {
+        QFontDialog dlg;
+        new KWindowStateSaver(&dlg, "topLevelDialogTest");
+        dlg.show();
+        QTest::qWait(10); // give the window time to show up, so we simulate a user-triggered resize
+        dlg.resize(dlgSize);
+        QTest::qWait(500); // give the state saver time to trigger
+        QCOMPARE(dlg.size(), dlgSize);
+    }
+
+    QVERIFY(cfg->hasGroup("topLevelDialogTest"));
+
+    {
+        QFontDialog dlg;
+        new KWindowStateSaver(&dlg, "topLevelDialogTest");
+        dlg.show();
+        QTest::qWait(100); // give the window time to show up properly
+        QCOMPARE(dlg.size(), dlgSize);
+    }
+}
+
+void KWindowStateSaverTest::testSubDialog()
+{
+    QWidget mainWindow;
+    mainWindow.show();
+    QTest::qWait(10);
+
+    auto cfg = KSharedConfig::openStateConfig();
+    cfg->deleteGroup("subDialogTest");
+    QSize dlgSize(700, 500);
+
+    {
+        auto dlg = new QFontDialog(&mainWindow);
+        new KWindowStateSaver(dlg, "subDialogTest");
+        dlg->show();
+        QTest::qWait(10); // give the window time to show up, so we simulate a user-triggered resize
+        dlg->resize(dlgSize);
+        QTest::qWait(500); // give the state saver time to trigger
+        QCOMPARE(dlg->size(), dlgSize);
+        delete dlg;
+    }
+
+    QVERIFY(cfg->hasGroup("subDialogTest"));
+
+    {
+        auto dlg = new QFontDialog(&mainWindow);
+        new KWindowStateSaver(dlg, "subDialogTest");
+        dlg->show();
+        QTest::qWait(100); // give the window time to show up properly
+        QCOMPARE(dlg->size(), dlgSize);
+    }
+}
+
+QTEST_MAIN(KWindowStateSaverTest)
+#include "kwindowstatesavertest.moc"