lockscreen: Dynamically load status bar and action drawer as needed for performance

Currently the lockscreen takes 5 seconds to load for me on the OnePlus 6. This MR moves the quicksettings and status bar to only load once the initial lockscreen has loaded (to avoid blocking it). This brings it down the initial load to 1 second for me.

components/mobileshell/qml/actiondrawer/ActionDrawerOpenSurface.qml

@@ -18,8 +18,6 @@ MobileShell.SwipeArea {
 
     required property ActionDrawer actionDrawer
 
-    property int oldMouseY: 0
-
     function startSwipe() {
         if (actionDrawer.visible) {
             // ensure the action drawer state is consistent

shell/contents/lockscreen/HeaderComponent.qml

@@ -21,9 +21,23 @@ Item {
 
     signal passwordRequested()
 
-    // top status bar
-    MobileShell.StatusBar {
-        id: statusBar
+    // The status bar and quicksettings take a while to load, don't pause initial lockscreen loading for it
+    Timer {
+        id: loadTimer
+        running: true
+        repeat: false
+        onTriggered: {
+            statusBarLoader.active = true
+            actionDrawerLoader.active = true
+        }
+    }
+
+    // Status bar
+    Loader {
+        id: statusBarLoader
+        active: false
+        asynchronous: true
+        visible: status == Loader.Ready
 
         anchors.top: parent.top
         anchors.left: parent.left
@@ -31,6 +45,14 @@ Item {
 
         height: root.statusBarHeight
 
+        sourceComponent: MobileShell.StatusBar {
+            id: statusBar
+
+            anchors.top: parent.top
+            anchors.left: parent.left
+            anchors.right: parent.right
+            height: root.statusBarHeight
+
             Kirigami.Theme.inherit: false
             Kirigami.Theme.colorSet: Kirigami.Theme.Complementary
 
@@ -41,15 +63,29 @@ Item {
             showTime: false
             disableSystemTray: true // prevent SIGABRT, since loading the system tray on the lockscreen leads to bad... things
         }
-
-    // drag down gesture to open action drawer
-    MobileShell.ActionDrawerOpenSurface {
-        id: swipeArea
-        actionDrawer: drawer
-        anchors.fill: statusBar
     }
 
-    // action drawer component
+    // Drag down gesture to open action drawer
+    MobileShell.ActionDrawerOpenSurface {
+        id: swipeArea
+        actionDrawer: actionDrawerLoader.item ? actionDrawerLoader.item.actionDrawer : null
+
+        anchors.fill: statusBarLoader
+    }
+
+    // Dynamically load on swipe-down to avoid having to load at start
+    Loader {
+        id: actionDrawerLoader
+        active: false
+        asynchronous: true
+        visible: status == Loader.Ready
+
+        anchors.fill: parent
+
+        sourceComponent: Item {
+            property var actionDrawer: drawer
+
+            // Action drawer component
             MobileShell.ActionDrawer {
                 id: drawer
                 anchors.fill: parent
@@ -85,4 +121,6 @@ Item {
                     drawer.requestNotificationAction = false;
                 }
             }
+        }
+    }
 }

shell/contents/lockscreen/LockScreen.qml

@@ -69,21 +69,15 @@ Item {
         anchors.fill: parent
 
         // Header bar and action drawer
-        Loader {
-            id: headerBarLoader
-            z: 1 // on top of flick area
-            readonly property real statusBarHeight: Kirigami.Units.gridUnit * 1.25
-
+        HeaderComponent {
+            id: headerBar
+            z: 1
             anchors.fill: parent
-            asynchronous: true
-
-            sourceComponent: HeaderComponent {
-                statusBarHeight: headerBarLoader.statusBarHeight
+            statusBarHeight: Kirigami.Units.gridUnit * 1.25
             openFactor: flickable.openFactor
             notificationsModel: root.notifModel
             onPasswordRequested: root.askPassword()
         }
-        }
 
         FlickContainer {
             id: flickable
@@ -120,7 +114,7 @@ Item {
                 onNotificationsShownChanged: root.notificationsShown = notificationsShown
                 onPasswordRequested: flickable.goToOpenPosition()
 
-                anchors.topMargin: headerBarLoader.statusBarHeight
+                anchors.topMargin: headerBar.statusBarHeight
                 anchors.top: parent.top
                 anchors.bottom: parent.bottom
                 anchors.left: parent.left