commit d8339715e428ea3d5eb2cc12388d85996e44ac9c
Author: David Edmundson <kde@davidedmundson.co.uk>
Date:   Thu Jun 13 13:27:17 2019 +0100

    Allow QtQuick applets and wallpapers to defer UiReadyConstraint - V1

diff --git a/src/scriptengines/qml/plasmoid/appletinterface.cpp b/src/scriptengines/qml/plasmoid/appletinterface.cpp
index 41c8d423c..afb6f69bf 100644
--- a/src/scriptengines/qml/plasmoid/appletinterface.cpp
+++ b/src/scriptengines/qml/plasmoid/appletinterface.cpp
@@ -169,7 +169,9 @@ void AppletInterface::init()
     geometryChanged(QRectF(), QRectF(x(), y(), width(), height()));
     emit busyChanged();
 
-    applet()->updateConstraints(Plasma::Types::UiReadyConstraint);
+    updateUiReadyConstraint();
+
+    connect(this, &AppletInterface::isLoadingChanged, this, &AppletInterface::updateUiReadyConstraint);
 
     connect(applet(), &Plasma::Applet::activated, this,
     [ = ]() {
@@ -851,5 +853,16 @@ bool AppletInterface::eventFilter(QObject *watched, QEvent *event)
     return AppletQuickItem::eventFilter(watched, event);
 }
 
+void AppletInterface::updateUiReadyConstraint()
+{
+    if (!isLoading()) {
+        applet()->updateConstraints(Plasma::Types::UiReadyConstraint);
+    }
+}
+
+bool AppletInterface::isLoading() const
+{
+    return m_loading;
+}
 
 #include "moc_appletinterface.cpp"
diff --git a/src/scriptengines/qml/plasmoid/appletinterface.h b/src/scriptengines/qml/plasmoid/appletinterface.h
index f09f99f48..9f75b5e47 100644
--- a/src/scriptengines/qml/plasmoid/appletinterface.h
+++ b/src/scriptengines/qml/plasmoid/appletinterface.h
@@ -238,6 +238,8 @@ class AppletInterface : public PlasmaQuick::AppletQuickItem
      */
     Q_PROPERTY(QVariantList availableScreenRegion READ availableScreenRegion NOTIFY availableScreenRegionChanged)
 
+    Q_PROPERTY(bool loading MEMBER m_loading NOTIFY isLoadingChanged)
+
 public:
     AppletInterface(DeclarativeAppletScript *script, const QVariantList &args = QVariantList(), QQuickItem *parent = nullptr);
     ~AppletInterface() override;
@@ -448,6 +450,8 @@ Q_SIGNALS:
     void configurationRequiredChanged();
     void configurationRequiredReasonChanged();
 
+    void isLoadingChanged();
+
 protected Q_SLOTS:
     void init() override;
 
@@ -455,6 +459,15 @@ protected:
     bool event(QEvent *event) override;
     bool eventFilter(QObject *watched, QEvent *event) override;
 
+   /*
+   * Returns true if this plasmoid or a dependent feature (i.e wallpaper) is loading
+   */
+    virtual bool isLoading() const;
+   /*
+   * Set UIReadyConstraint if we're not currently loading
+   */
+    void updateUiReadyConstraint();
+
 private Q_SLOTS:
     void destroyedChanged(bool destroyed);
 
@@ -474,6 +487,7 @@ private:
     QVariantList m_args;
     Plasma::Types::BackgroundHints m_backgroundHints;
     bool m_hideOnDeactivate : 1;
+    bool m_loading = false;
     //this is used to build an emacs style shortcut
     int m_oldKeyboardShortcut;
     QObject *m_dummyNativeInterface;
diff --git a/src/scriptengines/qml/plasmoid/containmentinterface.cpp b/src/scriptengines/qml/plasmoid/containmentinterface.cpp
index db0d8b9d1..cd06ec92f 100644
--- a/src/scriptengines/qml/plasmoid/containmentinterface.cpp
+++ b/src/scriptengines/qml/plasmoid/containmentinterface.cpp
@@ -860,6 +860,8 @@ void ContainmentInterface::loadWallpaper()
         //Qml seems happier if the parent gets set in this way
         m_wallpaperInterface->setProperty("parent", QVariant::fromValue(this));
 
+        connect(m_wallpaperInterface, &WallpaperInterface::isLoadingChanged, this, &AppletInterface::updateUiReadyConstraint);
+
         //set anchors
         QQmlExpression expr(qmlObject()->engine()->rootContext(), m_wallpaperInterface, QStringLiteral("parent"));
         QQmlProperty prop(m_wallpaperInterface, QStringLiteral("anchors.fill"));
@@ -1216,4 +1218,14 @@ void ContainmentInterface::addContainmentActions(QMenu *desktopMenu, QEvent *eve
     return;
 }
 
+bool ContainmentInterface::isLoading() const
+{
+    bool loading = AppletInterface::isLoading();
+    if (m_wallpaperInterface) {
+        loading &= m_wallpaperInterface->isLoading();
+    }
+    return loading;
+}
+
+
 #include "moc_containmentinterface.cpp"
diff --git a/src/scriptengines/qml/plasmoid/containmentinterface.h b/src/scriptengines/qml/plasmoid/containmentinterface.h
index 34a3f2f8c..ef4e54c6e 100644
--- a/src/scriptengines/qml/plasmoid/containmentinterface.h
+++ b/src/scriptengines/qml/plasmoid/containmentinterface.h
@@ -168,6 +168,8 @@ protected:
     void addAppletActions(QMenu *desktopMenu, Plasma::Applet *applet, QEvent *event);
     void addContainmentActions(QMenu *desktopMenu, QEvent *event);
 
+    virtual bool isLoading() const override;
+
 Q_SIGNALS:
     /**
      * Emitted when an applet is added
diff --git a/src/scriptengines/qml/plasmoid/wallpaperinterface.cpp b/src/scriptengines/qml/plasmoid/wallpaperinterface.cpp
index 2269fee3b..d1988b566 100644
--- a/src/scriptengines/qml/plasmoid/wallpaperinterface.cpp
+++ b/src/scriptengines/qml/plasmoid/wallpaperinterface.cpp
@@ -266,4 +266,10 @@ WallpaperInterface * WallpaperInterface::qmlAttachedProperties(QObject* object)
     return object->parent() ? nullptr : s_rootObjects.value(QtQml::qmlEngine(object));
 }
 
+bool WallpaperInterface::isLoading() const
+{
+    return m_loading;
+}
+
+
 #include "moc_wallpaperinterface.cpp"
diff --git a/src/scriptengines/qml/plasmoid/wallpaperinterface.h b/src/scriptengines/qml/plasmoid/wallpaperinterface.h
index b315f519d..daea6a80a 100644
--- a/src/scriptengines/qml/plasmoid/wallpaperinterface.h
+++ b/src/scriptengines/qml/plasmoid/wallpaperinterface.h
@@ -49,6 +49,7 @@ class WallpaperInterface : public QQuickItem
 
     Q_PROPERTY(QString pluginName READ pluginName NOTIFY packageChanged)
     Q_PROPERTY(KDeclarative::ConfigPropertyMap *configuration READ configuration NOTIFY configurationChanged)
+    Q_PROPERTY(bool loading MEMBER m_loading NOTIFY isLoadingChanged)
 
 public:
     explicit WallpaperInterface(ContainmentInterface *parent = nullptr);
@@ -86,9 +87,12 @@ public:
 
     static WallpaperInterface *qmlAttachedProperties(QObject *object);
 
+    bool isLoading() const;
+
 Q_SIGNALS:
     void packageChanged();
     void configurationChanged();
+    void isLoadingChanged();
 
 private Q_SLOTS:
     void syncWallpaperPackage();
@@ -103,6 +107,7 @@ private:
     KDeclarative::ConfigPropertyMap *m_configuration;
     KConfigLoader *m_configLoader;
     KActionCollection *m_actions;
+    bool m_loading = false;
 
     static QHash<QObject *, WallpaperInterface *> s_rootObjects;
 };