lockscreen: Reset state when screen is off

Wipe a partially entered password, and the open state of the lockscreen when the screen is off.
Addresses https://invent.kde.org/plasma/plasma-mobile/-/issues/110

components/CMakeLists.txt

@@ -10,3 +10,4 @@ add_subdirectory(quicksettingsplugin)
 add_subdirectory(windowplugin)
 add_subdirectory(shellsettingsplugin)
 add_subdirectory(wallpaperimageplugin)
+add_subdirectory(dpmsplugin)

components/dpmsplugin/CMakeLists.txt

@@ -0,0 +1,16 @@
+# SPDX-FileCopyrightText: 2024 Devin Lin <devin@kde.org>
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+ecm_add_qml_module(dpmsplugin URI org.kde.plasma.private.mobileshell.dpmsplugin GENERATE_PLUGIN_SOURCE)
+
+target_sources(dpmsplugin PRIVATE dpmsutil.cpp)
+
+target_link_libraries(dpmsplugin PRIVATE
+    Qt::Qml
+    Qt::DBus
+    Qt::Gui
+    Qt::Quick
+    KF6::ScreenDpms
+)
+
+ecm_finalize_qml_module(dpmsplugin)

components/dpmsplugin/dpmsutil.cpp

@@ -0,0 +1,35 @@
+//  SPDX-FileCopyrightText: 2024 Devin Lin <devin@kde.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "dpmsutil.h"
+
+#include <QGuiApplication>
+
+DPMSUtil::DPMSUtil(QObject *parent)
+    : QObject{parent}
+    , m_dpms(new KScreen::Dpms)
+{
+    connect(m_dpms.get(), &KScreen::Dpms::modeChanged, this, [this](auto mode, auto screen) {
+        switch (mode) {
+        case KScreen::Dpms::On:
+            Q_EMIT dpmsTurnedOn(screen);
+            break;
+        case KScreen::Dpms::Off:
+        case KScreen::Dpms::Standby:
+        case KScreen::Dpms::Suspend:
+        default:
+            Q_EMIT dpmsTurnedOff(screen);
+            break;
+        }
+    });
+}
+
+void DPMSUtil::turnDpmsOn()
+{
+    m_dpms->switchMode(KScreen::Dpms::On);
+}
+
+void DPMSUtil::turnDpmsOff()
+{
+    m_dpms->switchMode(KScreen::Dpms::Off);
+}

components/dpmsplugin/dpmsutil.h

@@ -0,0 +1,37 @@
+// SPDX-FileCopyrightText: 2024 Devin Lin <devin@kde.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <QObject>
+#include <QPointer>
+#include <QQuickItem>
+#include <QQuickWindow>
+#include <QTimer>
+#include <qqmlregistration.h>
+
+#include <KScreenDpms/Dpms>
+
+/**
+ * Utility class that provides useful functions related to dpms.
+ *
+ * @author Devin Lin <devin@kde.org>
+ **/
+class DPMSUtil : public QObject
+{
+    Q_OBJECT
+    QML_ELEMENT
+
+public:
+    DPMSUtil(QObject *parent = nullptr);
+
+    Q_INVOKABLE void turnDpmsOn();
+    Q_INVOKABLE void turnDpmsOff();
+
+Q_SIGNALS:
+    void dpmsTurnedOn(QScreen *screen);
+    void dpmsTurnedOff(QScreen *screen);
+
+private:
+    QScopedPointer<KScreen::Dpms> m_dpms;
+};

shell/contents/lockscreen/LockScreen.qml

@@ -8,6 +8,8 @@ import QtQuick.Layouts
 
 import org.kde.plasma.core as PlasmaCore
 import org.kde.notificationmanager as Notifications
+import org.kde.plasma.private.mobileshell.dpmsplugin as DPMS
+
 
 import org.kde.kirigami 2.12 as Kirigami
 
@@ -64,6 +66,18 @@ Item {
         }
     }
 
+    // when screen turns off, reset state
+    DPMS.DPMSUtil {
+        id: dpms
+
+        onDpmsTurnedOff: (screen) => {
+            if (screen.name === Screen.name) {
+                flickable.goToClosePosition();
+                lockScreenState.resetPassword();
+            }
+        }
+    }
+
     Item {
         id: lockscreenContainer
         anchors.fill: parent