Introduce SharedQmlEngine class

Allows to drop the direct dependency on KDeclarative only used
for `QmlObjectSharedEngine` outside of `KCModuleQML`

Signed-off-by: Eike Hein <eike.hein@mbition.io>

src/libkwineffects/CMakeLists.txt

@@ -43,6 +43,7 @@ set(kwin_EFFECTSLIB_SRCS
     kwinoffscreenquickview.cpp
     kwinquickeffect.cpp
     logging.cpp
+    sharedqmlengine.cpp
 )
 
 add_library(kwineffects SHARED ${kwin_EFFECTSLIB_SRCS})
@@ -55,7 +56,7 @@ target_link_libraries(kwineffects
         XCB::XCB
     PRIVATE
         Qt::Quick
-        KF5::Declarative
+        KF5::I18n
         kwinglutils
 )
 set_target_properties(kwineffects PROPERTIES

src/libkwineffects/kwinoffscreenquickview.cpp

@@ -11,12 +11,14 @@
 
 #include "kwinglutils.h"
 #include "logging_p.h"
+#include "sharedqmlengine.h"
 
 #include <QGuiApplication>
 #include <QQmlEngine>
 #include <QQuickItem>
 #include <QQmlContext>
 #include <QQmlComponent>
+#include <QQmlEngine>
 #include <QQuickView>
 #include <QQuickRenderControl>
 #include <QStyleHints>
@@ -26,8 +28,6 @@
 #include <QOpenGLFramebufferObject>
 #include <QTimer>
 
-#include <KDeclarative/QmlObjectSharedEngine>
-
 namespace KWin
 {
 
@@ -87,7 +87,15 @@ public:
 class Q_DECL_HIDDEN OffscreenQuickScene::Private
 {
 public:
-    KDeclarative::QmlObjectSharedEngine *qmlObject = nullptr;
+    Private()
+        : qmlEngine(SharedQmlEngine::engine())
+    {
+
+    }
+
+    SharedQmlEngine::Ptr qmlEngine;
+    QScopedPointer<QQmlComponent> qmlComponent;
+    QScopedPointer<QQuickItem> quickItem;
 };
 
 OffscreenQuickView::OffscreenQuickView(QObject *parent)
@@ -541,44 +549,53 @@ OffscreenQuickScene::OffscreenQuickScene(QObject *parent)
     : OffscreenQuickView(parent)
     , d(new OffscreenQuickScene::Private)
 {
-    d->qmlObject = new KDeclarative::QmlObjectSharedEngine(this);
 }
 
 OffscreenQuickScene::OffscreenQuickScene(QObject *parent, QWindow *renderWindow)
     : OffscreenQuickView(parent, renderWindow)
     , d(new OffscreenQuickScene::Private)
 {
-    d->qmlObject = new KDeclarative::QmlObjectSharedEngine(this);
 }
 
 OffscreenQuickScene::OffscreenQuickScene(QObject *parent, QWindow *renderWindow, ExportMode exportMode)
     : OffscreenQuickView(parent, renderWindow, exportMode)
     , d(new OffscreenQuickScene::Private)
 {
-    d->qmlObject = new KDeclarative::QmlObjectSharedEngine(this);
 }
 
 OffscreenQuickScene::OffscreenQuickScene(QObject *parent, OffscreenQuickView::ExportMode exportMode)
     : OffscreenQuickView(parent, exportMode)
     , d(new OffscreenQuickScene::Private)
 {
-    d->qmlObject = new KDeclarative::QmlObjectSharedEngine(this);
 }
 
-OffscreenQuickScene::~OffscreenQuickScene()
+OffscreenQuickScene::~OffscreenQuickScene() = default;
-{
-    delete d->qmlObject;
-}
 
 void OffscreenQuickScene::setSource(const QUrl &source)
 {
-    d->qmlObject->setSource(source);
+    if (!d->qmlComponent) {
+        d->qmlComponent.reset(new QQmlComponent(d->qmlEngine.data()));
+    }
 
-    QQuickItem *item = rootItem();
+    d->qmlComponent->loadUrl(source);
-    if (!item) {
+    if (d->qmlComponent->isError()) {
-        qCDebug(LIBKWINEFFECTS) << "Could not load effect quick view" << source;
+        qCWarning(LIBKWINEFFECTS).nospace() << "Failed to load effect quick view " << source << ": " << d->qmlComponent->errors();
+        d->qmlComponent.reset();
         return;
     }
+
+    d->quickItem.reset();
+
+    QScopedPointer<QObject> qmlObject(d->qmlComponent->create());
+    QQuickItem *item = qobject_cast<QQuickItem *>(qmlObject.data());
+    if (!item) {
+        qCWarning(LIBKWINEFFECTS) << "Root object of effect quick view" << source << "is not a QQuickItem";
+        return;
+    }
+
+    qmlObject.take();
+    d->quickItem.reset(item);
+
     item->setParentItem(contentItem());
 
     auto updateSize = [item, this]() { item->setSize(contentItem()->size()); };
@@ -589,12 +606,12 @@ void OffscreenQuickScene::setSource(const QUrl &source)
 
 QQmlContext *OffscreenQuickScene::rootContext() const
 {
-    return d->qmlObject->rootContext();
+    return d->qmlEngine->rootContext();
 }
 
 QQuickItem *OffscreenQuickScene::rootItem() const
 {
-    return qobject_cast<QQuickItem *>(d->qmlObject->rootObject());
+    return d->quickItem.data();
 }
 
 } // namespace KWin

src/libkwineffects/kwinquickeffect.cpp

@@ -6,9 +6,10 @@
 
 #include "kwinquickeffect.h"
 
-#include <KDeclarative/QmlObjectSharedEngine>
+#include "sharedqmlengine.h"
 
 #include <QQuickItem>
+#include <QQmlEngine>
 #include <QWindow>
 
 namespace KWin
@@ -19,7 +20,7 @@ class QuickSceneEffectPrivate
 public:
     static QuickSceneEffectPrivate *get(QuickSceneEffect *effect) { return effect->d.data(); }
 
-    QScopedPointer<KDeclarative::QmlObjectSharedEngine> qmlEngine;
+    SharedQmlEngine::Ptr qmlEngine;
     QScopedPointer<QQmlComponent> qmlComponent;
     QUrl source;
     QHash<EffectScreen *, QuickSceneView *> views;
@@ -254,11 +255,11 @@ void QuickSceneEffect::startInternal()
     }
 
     if (!d->qmlEngine) {
-        d->qmlEngine.reset(new KDeclarative::QmlObjectSharedEngine(this));
+        d->qmlEngine = SharedQmlEngine::engine();
     }
 
     if (!d->qmlComponent) {
-        d->qmlComponent.reset(new QQmlComponent(d->qmlEngine->engine()));
+        d->qmlComponent.reset(new QQmlComponent(d->qmlEngine.data()));
         d->qmlComponent->loadUrl(d->source);
         if (d->qmlComponent->isError()) {
             qWarning().nospace() << "Failed to load " << d->source << ": " << d->qmlComponent->errors();

src/libkwineffects/sharedqmlengine.cpp

@@ -0,0 +1,35 @@
+/*
+    SPDX-FileCopyrightText: 2022 MBition GmbH
+    SPDX-FileContributor: Kai Uwe Broulik <kai_uwe.broulik@mbition.io>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+
+#include "sharedqmlengine.h"
+
+#include <QQmlContext>
+#include <QQmlEngine>
+
+#include <KLocalizedContext>
+
+namespace KWin
+{
+
+QWeakPointer<QQmlEngine> SharedQmlEngine::s_engine;
+
+SharedQmlEngine::Ptr SharedQmlEngine::engine()
+{
+    if (!s_engine) {
+        Ptr ptr(new QQmlEngine());
+
+        auto *i18nContext = new KLocalizedContext(ptr.data());
+        ptr->rootContext()->setContextObject(i18nContext);
+
+        s_engine = ptr;
+        return ptr;
+    }
+
+    return s_engine.toStrongRef();
+}
+
+} // namespace KWin

src/libkwineffects/sharedqmlengine.h

@@ -0,0 +1,27 @@
+/*
+    SPDX-FileCopyrightText: 2022 MBition GmbH
+    SPDX-FileContributor: Kai Uwe Broulik <kai_uwe.broulik@mbition.io>
+
+    SPDX-License-Identifier: GPL-2.0-or-later
+*/
+
+#pragma once
+
+#include <QSharedPointer>
+
+class QQmlEngine;
+
+namespace KWin
+{
+
+class SharedQmlEngine
+{
+public:
+    using Ptr = QSharedPointer<QQmlEngine>;
+    static Ptr engine();
+
+private:
+    static QWeakPointer<QQmlEngine> s_engine;
+};
+
+} // namespace KWin