QmlDesigner: Introduce SkipIterator

Instead of having a cache using an iterator skipping entries is much
easier because the cache has not to be anymore updated. When we get
C++ 20 ranges use them instead.

Change-Id: If5b45c53bbd0b12138328862ac152788ffd911b2
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

5 files changed, 111 insertions, 27 deletions

diff --git a/src/plugins/qmldesigner/CMakeLists.txt b/src/plugins/qmldesigner/CMakeLists.txt
index b9459aeb1b..c7989fda36 100644
--- a/src/plugins/qmldesigner/CMakeLists.txt
+++ b/src/plugins/qmldesigner/CMakeLists.txt
@@ -371,6 +371,7 @@ extend_qtc_library(QmlDesignerCore
     rewriteactioncompressor.h
     rewriterview.cpp
     signalhandlerproperty.cpp
+    skipiterator.h
     stylesheetmerger.cpp
     textmodifier.cpp
     texttomodelmerger.cpp
diff --git a/src/plugins/qmldesigner/designercore/model/abstractview.cpp b/src/plugins/qmldesigner/designercore/model/abstractview.cpp
index 07692f4a10..a09db03dac 100644
--- a/src/plugins/qmldesigner/designercore/model/abstractview.cpp
+++ b/src/plugins/qmldesigner/designercore/model/abstractview.cpp
@@ -143,9 +143,6 @@ The default implementation is setting the reference of the model to the view.
 void AbstractView::modelAttached(Model *model)
 {
     setModel(model);
-
-    if (model)
-        model->d->updateEnabledViews();
 }
 
 /*!
@@ -617,9 +614,6 @@ bool AbstractView::isEnabled() const
 void AbstractView::setEnabled(bool b)
 {
     m_enabled = b;
-
-    if (model())
-        model()->d->updateEnabledViews();
 }
 
 QList<ModelNode> AbstractView::allModelNodes() const
diff --git a/src/plugins/qmldesigner/designercore/model/model.cpp b/src/plugins/qmldesigner/designercore/model/model.cpp
index e630cc96d8..fcdb66b802 100644
--- a/src/plugins/qmldesigner/designercore/model/model.cpp
+++ b/src/plugins/qmldesigner/designercore/model/model.cpp
@@ -96,7 +96,6 @@ void ModelPrivate::detachAllViews()
         detachView(view.data(), true);
 
     m_viewList.clear();
-    updateEnabledViews();
 
     if (m_nodeInstanceView) {
         m_nodeInstanceView->modelAboutToBeDetached(m_model);
@@ -299,9 +298,9 @@ void ModelPrivate::removeNodeFromModel(const InternalNodePointer &node)
     m_internalIdNodeHash.remove(node->internalId);
 }
 
-const QList<QPointer<AbstractView>> ModelPrivate::enabledViews() const
+EnabledViewRange ModelPrivate::enabledViews() const
 {
-    return m_enabledViewList;
+    return EnabledViewRange{m_viewList};
 }
 
 void ModelPrivate::removeAllSubNodes(const InternalNodePointer &node)
@@ -754,7 +753,6 @@ void ModelPrivate::detachView(AbstractView *view, bool notifyView)
     if (notifyView)
         view->modelAboutToBeDetached(m_model);
     m_viewList.removeOne(view);
-    updateEnabledViews();
 }
 
 void ModelPrivate::notifyNodeCreated(const InternalNodePointer &newInternalNodePointer)
@@ -1317,13 +1315,6 @@ InternalNodePointer ModelPrivate::currentTimelineNode() const
     return m_currentTimelineNode;
 }
 
-void ModelPrivate::updateEnabledViews()
-{
-    m_enabledViewList = Utils::filtered(m_viewList, [](QPointer<AbstractView> view) {
-        return view->isEnabled();
-    });
-}
-
 InternalNodePointer ModelPrivate::nodeForId(const QString &id) const
 {
     return m_idNodeHash.value(id);
diff --git a/src/plugins/qmldesigner/designercore/model/model_p.h b/src/plugins/qmldesigner/designercore/model/model_p.h
index d167819280..ce2a49fc42 100644
--- a/src/plugins/qmldesigner/designercore/model/model_p.h
+++ b/src/plugins/qmldesigner/designercore/model/model_p.h
@@ -3,17 +3,20 @@
 
 #pragma once
 
+#include "qmldesignercorelib_global.h"
+
+#include "abstractview.h"
+#include "metainfo.h"
+#include "modelnode.h"
+#include "skipiterator.h"
+
 #include <QList>
 #include <QPointer>
 #include <QSet>
 #include <QUrl>
 #include <QVector3D>
 
-#include "modelnode.h"
-#include "abstractview.h"
-#include "metainfo.h"
-
-#include "qmldesignercorelib_global.h"
+#include <algorithm>
 
 QT_BEGIN_NAMESPACE
 class QPlainTextEdit;
@@ -64,7 +67,28 @@ private:
     QPointer<ModelPrivate> m_model;
 };
 
-class ModelPrivate : public QObject {
+struct Increment
+{
+    using iterator = QList<QPointer<AbstractView>>::const_iterator;
+    auto operator()(iterator current) {
+        return std::find_if(std::next(current),
+                            end,
+                            [] (iterator::reference &view) { return view && view->isEnabled(); });
+    }
+
+   iterator end;
+};
+
+class EnabledViewRange : public SkipRange<QList<QPointer<AbstractView>>, Increment>
+{
+public:
+    EnabledViewRange(const container &views)
+        : base{views, Increment{views.end()}}
+    {}
+};
+
+class ModelPrivate : public QObject
+{
     Q_OBJECT
 
     friend Model;
@@ -249,8 +273,6 @@ public:
     InternalNodePointer currentStateNode() const;
     InternalNodePointer currentTimelineNode() const;
 
-    void updateEnabledViews();
-
 private:
     void removePropertyWithoutNotification(const InternalPropertyPointer &property);
     void removeAllSubNodes(const InternalNodePointer &node);
@@ -259,7 +281,7 @@ private:
     QList<ModelNode> toModelNodeList(const QList<InternalNodePointer> &nodeList, AbstractView *view) const;
     QVector<ModelNode> toModelNodeVector(const QVector<InternalNodePointer> &nodeVector, AbstractView *view) const;
     QVector<InternalNodePointer> toInternalNodeVector(const QVector<ModelNode> &modelNodeVector) const;
-    const QList<QPointer<AbstractView>> enabledViews() const;
+    EnabledViewRange enabledViews() const;
 
 public:
     NotNullPointer<ProjectStorageType> projectStorage = nullptr;
@@ -271,7 +293,6 @@ private:
     Imports m_possibleImportList;
     Imports m_usedImportList;
     QList<QPointer<AbstractView>> m_viewList;
-    QList<QPointer<AbstractView>> m_enabledViewList;
     QList<InternalNodePointer> m_selectedInternalNodeList;
     QHash<QString,InternalNodePointer> m_idNodeHash;
     QHash<qint32, InternalNodePointer> m_internalIdNodeHash;
diff --git a/src/plugins/qmldesigner/designercore/model/skipiterator.h b/src/plugins/qmldesigner/designercore/model/skipiterator.h
new file mode 100644
index 0000000000..11efb7d97f
--- /dev/null
+++ b/src/plugins/qmldesigner/designercore/model/skipiterator.h
@@ -0,0 +1,77 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#pragma once
+
+#include <iterator>
+
+namespace QmlDesigner {
+
+template<typename BaseIterator, typename Increment>
+class SkipIterator
+{
+public:
+    using iterator_category = std::forward_iterator_tag;
+    using difference_type = qsizetype;
+    using value_type = typename BaseIterator::value_type;
+    using pointer = typename BaseIterator::pointer;
+    using reference = typename BaseIterator::reference;
+
+    SkipIterator() = default;
+    SkipIterator(BaseIterator current, Increment increment)
+        : m_current{current}
+        , m_increment{std::move(increment)}
+    {}
+
+    SkipIterator operator++()
+    {
+        m_current = m_increment(m_current);
+        return *this;
+    }
+
+    SkipIterator operator++(int)
+    {
+        auto tmp = *this;
+        m_current = m_increment(m_current);
+        return tmp;
+    }
+
+    reference operator*() const { return *m_current; }
+    pointer operator->() const { return m_current.operator->(); }
+
+    friend bool operator==(const SkipIterator &first, const SkipIterator &second)
+    {
+        return first.m_current == second.m_current;
+    }
+
+    friend bool operator!=(const SkipIterator &first, const SkipIterator &second)
+    {
+        return first.m_current != second.m_current;
+    }
+
+private:
+    BaseIterator m_current = {};
+    Increment m_increment;
+};
+
+template<typename Container, typename Increment>
+class SkipRange
+{
+public:
+    using container = Container;
+    using base = SkipRange<Container, Increment>;
+    using iterator = SkipIterator<typename Container::const_iterator, Increment>;
+
+    SkipRange(const Container &container, Increment increment)
+        : m_begin{container.begin(), increment}
+        , m_end{container.end(), increment}
+    {}
+
+    iterator begin() const { return m_begin; }
+    iterator end() const { return m_end; }
+
+private:
+    iterator m_begin;
+    iterator m_end;
+};
+} // namespace QmlDesigner