qml: Introduce node attribute cache

The QOpcUaNode attributeUpdated signal is emitted even when the actual
value has not changed.

Change-Id: Ib8e232d03903e7442244eccf4f20b607e8c40d39
Reviewed-by: Frank Meerkoetter <frank.meerkoetter@basyskom.com>

9 files changed, 312 insertions, 44 deletions

diff --git a/src/imports/opcua/opcua.pro b/src/imports/opcua/opcua.pro
index 93429b1..cfc94a4 100644
--- a/src/imports/opcua/opcua.pro
+++ b/src/imports/opcua/opcua.pro
@@ -11,7 +11,9 @@ SOURCES += \
     opcuarelativenodeid.cpp \
     opcuanodeidtype.cpp \
     universalnode.cpp \
-    opcuapathresolver.cpp
+    opcuapathresolver.cpp \
+    opcuaattributevalue.cpp \
+    opcuaattributecache.cpp
 
 HEADERS += \
     opcua_plugin.h \
@@ -24,7 +26,9 @@ HEADERS += \
     opcuarelativenodeid.h \
     opcuanodeidtype.h \
     universalnode.h \
-    opcuapathresolver.h
+    opcuapathresolver.h \
+    opcuaattributecache.h \
+    opcuaattributevalue.h
 
 load(qml_plugin)
 
diff --git a/src/imports/opcua/opcuaattributecache.cpp b/src/imports/opcua/opcuaattributecache.cpp
new file mode 100644
index 0000000..b57acc8
--- /dev/null
+++ b/src/imports/opcua/opcuaattributecache.cpp
@@ -0,0 +1,86 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt OPC UA module.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "opcuaattributecache.h"
+#include "opcuaattributevalue.h"
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class OpcUaAttributeCache
+    \inqmlmodule QtOpcUa
+    \brief Flexible attribute value cache providing signals.
+    \internal
+
+    This class is just for internal use in the declarative backend and not exposed to users.
+
+    It caches node attribute values and provides accesss. Main purpose is to
+    let \l OpcUaAttributeValue provide separate value change signals for each attribute.
+
+    \sa OpcUaAttributeValue
+*/
+
+OpcUaAttributeCache::OpcUaAttributeCache(QObject *parent) : QObject(parent)
+{
+}
+
+void OpcUaAttributeCache::setAttributeValue(QOpcUa::NodeAttribute attr, const QVariant &value)
+{
+    attribute(attr)->setValue(value);
+}
+
+void OpcUaAttributeCache::invalidate()
+{
+    // Reset all values in the cache to invalid.
+    // Do not clear() the cache because there are still objects with
+    // connections waiting for notifications
+    for (auto i = m_attributeCache.constBegin(); i != m_attributeCache.constEnd(); ++i)
+        i.value()->invalidate();
+}
+
+OpcUaAttributeValue *OpcUaAttributeCache::attribute(QOpcUa::NodeAttribute attr)
+{
+    if (!m_attributeCache.contains(attr))
+        m_attributeCache.insert(attr, new OpcUaAttributeValue(this));
+    return m_attributeCache.value(attr);
+}
+
+const QVariant &OpcUaAttributeCache::attributeValue(QOpcUa::NodeAttribute attr)
+{
+    return attribute(attr)->value();
+}
+
+QT_END_NAMESPACE
diff --git a/src/imports/opcua/opcuaattributecache.h b/src/imports/opcua/opcuaattributecache.h
new file mode 100644
index 0000000..f9a761b
--- /dev/null
+++ b/src/imports/opcua/opcuaattributecache.h
@@ -0,0 +1,62 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt OPC UA module.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#pragma once
+
+#include "qopcuatype.h"
+#include <QObject>
+
+QT_BEGIN_NAMESPACE
+
+class OpcUaAttributeValue;
+
+class OpcUaAttributeCache : public QObject
+{
+    Q_OBJECT
+public:
+    explicit OpcUaAttributeCache(QObject *parent = nullptr);
+    OpcUaAttributeValue *attribute(QOpcUa::NodeAttribute attribute);
+    const QVariant &attributeValue(QOpcUa::NodeAttribute);
+
+public slots:
+    void setAttributeValue(QOpcUa::NodeAttribute attribute, const QVariant &value);
+    void invalidate();
+
+private:
+    QHash<QOpcUa::NodeAttribute, OpcUaAttributeValue *> m_attributeCache;
+};
+
+QT_END_NAMESPACE
diff --git a/src/imports/opcua/opcuaattributevalue.cpp b/src/imports/opcua/opcuaattributevalue.cpp
new file mode 100644
index 0000000..493d7d0
--- /dev/null
+++ b/src/imports/opcua/opcuaattributevalue.cpp
@@ -0,0 +1,88 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt OPC UA module.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "opcuaattributevalue.h"
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class OpcUaAttributeValue
+    \inqmlmodule QtOpcUa
+    \brief Stores an attribute value and provides a changed signal.
+    \internal
+
+    This class is just for internal use in the declarative backend and not exposed to users.
+
+    When setting the value it will emit a changed signal if the value has changed.
+
+    \sa OpcUaAttributeCache
+*/
+
+OpcUaAttributeValue::OpcUaAttributeValue(QObject *parent)
+    : QObject(parent)
+{
+
+}
+
+bool OpcUaAttributeValue::operator ==(const OpcUaAttributeValue &rhs)
+{
+    return m_value == rhs.m_value;
+}
+
+void OpcUaAttributeValue::setValue(const QVariant &value)
+{
+    if (value != m_value) {
+        m_value = value;
+        emit changed(m_value);
+    }
+}
+
+void OpcUaAttributeValue::invalidate()
+{
+    setValue(QVariant());
+}
+
+const QVariant &OpcUaAttributeValue::value() const
+{
+    return m_value;
+}
+
+OpcUaAttributeValue::operator QVariant() const
+{
+    return value();
+}
+
+QT_END_NAMESPACE
diff --git a/src/imports/opcua/opcuaattributevalue.h b/src/imports/opcua/opcuaattributevalue.h
new file mode 100644
index 0000000..a3c073c
--- /dev/null
+++ b/src/imports/opcua/opcuaattributevalue.h
@@ -0,0 +1,62 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt OPC UA module.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPLv3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#pragma once
+
+#include <QObject>
+#include <QVariant>
+
+QT_BEGIN_NAMESPACE
+
+class OpcUaAttributeValue : public QObject
+{
+    Q_OBJECT
+public:
+    explicit OpcUaAttributeValue(QObject *parent);
+    bool operator ==(const OpcUaAttributeValue &rhs);
+    void setValue(const QVariant &value);
+    void invalidate();
+    const QVariant &value() const;
+    operator QVariant() const;
+
+signals:
+    void changed(QVariant value);
+
+private:
+    QVariant m_value;
+};
+
+QT_END_NAMESPACE
diff --git a/src/imports/opcua/opcuanode.cpp b/src/imports/opcua/opcuanode.cpp
index b9d9025..fdb2188 100644
--- a/src/imports/opcua/opcuanode.cpp
+++ b/src/imports/opcua/opcuanode.cpp
@@ -41,6 +41,7 @@
 #include "opcuarelativenodepath.h"
 #include "opcuarelativenodeid.h"
 #include "opcuapathresolver.h"
+#include "opcuaattributevalue.h"
 #include <QOpcUaNode>
 #include <QOpcUaClient>
 #include <QLoggingCategory>
@@ -192,6 +193,8 @@ void OpcUaNode::setupNode(const QString &absoluteNodePath)
         qCWarning(QT_OPCUA_PLUGINS_QML) << "Invalid node:" << m_absoluteNodePath;
         return;
     }
+
+    connect(m_node, &QOpcUaNode::attributeUpdated, &m_attributeCache, &OpcUaAttributeCache::setAttributeValue);
 }
 
 void OpcUaNode::updateNode()
diff --git a/src/imports/opcua/opcuanode.h b/src/imports/opcua/opcuanode.h
index 821fac3..4466967 100644
--- a/src/imports/opcua/opcuanode.h
+++ b/src/imports/opcua/opcuanode.h
@@ -39,6 +39,7 @@
 #include <QObject>
 #include <qopcuatype.h>
 #include "universalnode.h"
+#include "opcuaattributecache.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -85,6 +86,7 @@ protected:
     QString m_absoluteNodePath; // not exposed
     bool m_readyToUse = false;
     UniversalNode m_resolvedNode;
+    OpcUaAttributeCache m_attributeCache;
 };
 
 QT_END_NAMESPACE
diff --git a/src/imports/opcua/opcuavaluenode.cpp b/src/imports/opcua/opcuavaluenode.cpp
index 83f9c13..98198b0 100644
--- a/src/imports/opcua/opcuavaluenode.cpp
+++ b/src/imports/opcua/opcuavaluenode.cpp
@@ -37,6 +37,7 @@
 #include "opcuavaluenode.h"
 #include "opcuaconnection.h"
 #include "opcuanodeid.h"
+#include "opcuaattributevalue.h"
 #include <QLoggingCategory>
 
 QT_BEGIN_NAMESPACE
@@ -77,11 +78,11 @@ Q_DECLARE_LOGGING_CATEGORY(QT_OPCUA_PLUGINS_QML)
 OpcUaValueNode::OpcUaValueNode(QObject *parent):
     OpcUaNode(parent)
 {
+    connect(m_attributeCache.attribute(QOpcUa::NodeAttribute::Value), &OpcUaAttributeValue::changed, this, &OpcUaValueNode::valueChanged);
 }
 
 OpcUaValueNode::~OpcUaValueNode()
 {
-
 }
 
 void OpcUaValueNode::setValue(const QVariant &value)
@@ -95,8 +96,7 @@ void OpcUaValueNode::setupNode(const QString &absolutePath)
     if (!m_node)
         return;
 
-    connect(m_node, &QOpcUaNode::attributeRead, this, &OpcUaValueNode::handleAttributeUpdate);
-    connect(m_node, &QOpcUaNode::dataChangeOccurred, this, &OpcUaValueNode::handleDataChangeOccurred);
+    connect(m_node, &QOpcUaNode::attributeRead, this, [this](){setReadyToUse(true);});
 
     if (!m_node->readAttributes(QOpcUa::NodeAttribute::Value
                             | QOpcUa::NodeAttribute::NodeClass
@@ -111,40 +111,6 @@ void OpcUaValueNode::setupNode(const QString &absolutePath)
         qCWarning(QT_OPCUA_PLUGINS_QML) << "Failed monitoring" << m_node->nodeId();
 }
 
-void OpcUaValueNode::handleAttributeUpdate(QOpcUa::NodeAttributes attrs)
-{
-    /*
-     if (attr & QOpcUa::NodeAttribute::NodeClass)
-         mNodeClass = mOpcNode->attribute(QOpcUa::NodeAttribute::NodeClass).value<QOpcUa::NodeClass>();
-     if (attr & QOpcUa::NodeAttribute::BrowseName)
-         mNodeBrowseName = mOpcNode->attribute(QOpcUa::NodeAttribute::BrowseName).value<QOpcUa::QQualifiedName>().name();
-     if (attr & QOpcUa::NodeAttribute::DisplayName)
-         mNodeDisplayName = mOpcNode->attribute(QOpcUa::NodeAttribute::DisplayName).value<QOpcUa::QLocalizedText>().text();
-     if (attr & QOpcUa::NodeAttribute::NodeId)
-         mNodeDisplayName = mOpcNode->attribute(QOpcUa::NodeAttribute::NodeId).toString();
-         */
-
-    if (attrs & QOpcUa::NodeAttribute::Value) {
-        const auto value = m_node->attribute(QOpcUa::NodeAttribute::Value);
-        if (value != m_cachedValue) {
-            m_cachedValue = value;
-            emit valueChanged(value);
-        }
-    }
-
-    setReadyToUse();
-}
-
-void OpcUaValueNode::handleDataChangeOccurred(QOpcUa::NodeAttribute attr, QVariant value)
-{
-    if (attr == QOpcUa::NodeAttribute::Value) {
-        if (value != m_cachedValue) {
-            m_cachedValue = value;
-            emit valueChanged(value);
-        }
-    }
-}
-
 QVariant OpcUaValueNode::value() const
 {
     if (!m_node)
diff --git a/src/imports/opcua/opcuavaluenode.h b/src/imports/opcua/opcuavaluenode.h
index 1d892a9..cab3474 100644
--- a/src/imports/opcua/opcuavaluenode.h
+++ b/src/imports/opcua/opcuavaluenode.h
@@ -59,11 +59,6 @@ signals:
 
 private slots:
     void setupNode(const QString &absolutePath) override;
-    void handleAttributeUpdate(QOpcUa::NodeAttributes attrs);
-    void handleDataChangeOccurred(QOpcUa::NodeAttribute attr, QVariant value);
-
- private:
-    QVariant m_cachedValue;
 };
 
 QT_END_NAMESPACE