[quick] Fix slow value relation widget

If value relation widget in qgis_quick was populated with lots of items, it was getting very slow - this was due to the use of ListModel QML item. The fix introduces a c++ based model which is fast to populate and look up values in the list.
qgis · Mar 13, 2020 · 31ee21d · 31ee21d
1 parent 5552e12
commit 31ee21d
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Showing 7 changed files with 149 additions and 28 deletions.
diff --git a/src/quickgui/CMakeLists.txt b/src/quickgui/CMakeLists.txt
@@ -18,6 +18,7 @@ SET(QGIS_QUICK_GUI_MOC_HDRS
   qgsquickscalebarkit.h
   qgsquicksimulatedpositionsource.h
   qgsquickutils.h
+  qgsquickvaluerelationlistmodel.h
 )
 
 SET(QGIS_QUICK_GUI_HDRS
@@ -43,6 +44,7 @@ SET(QGIS_QUICK_GUI_SRC
   qgsquickscalebarkit.cpp
   qgsquicksimulatedpositionsource.cpp
   qgsquickutils.cpp
+  qgsquickvaluerelationlistmodel.cpp
 )
 
 INCLUDE_DIRECTORIES(

diff --git a/src/quickgui/plugin/editor/qgsquickeditorwidgetcombobox.qml b/src/quickgui/plugin/editor/qgsquickeditorwidgetcombobox.qml
@@ -44,7 +44,7 @@ ComboBox {
   delegate: ItemDelegate {
     width: comboBox.width
     height: comboBox.height * 0.8
-    text: modelData
+    text: model.display
     font.weight: comboBox.currentIndex === index ? Font.DemiBold : Font.Normal
     font.pixelSize: comboStyle.fontPixelSize
     highlighted: comboBox.highlightedIndex == index

diff --git a/src/quickgui/plugin/editor/qgsquickvaluemap.qml b/src/quickgui/plugin/editor/qgsquickvaluemap.qml
@@ -41,7 +41,7 @@ Item {
     property var currentValue: value
 
     comboStyle: customStyle.fields
-    textRole: 'text'
+    textRole: 'display'
     height: parent.height
     model: ListModel {
       id: listModel
@@ -57,7 +57,7 @@ Item {
           {
             var currentMap = config['map'][i]
             var currentKey = Object.keys(currentMap)[0]
-            listModel.append( { text: currentKey } )
+            listModel.append( { display: currentKey } )
             reverseConfig[currentMap[currentKey]] = currentKey;
           }
         }
@@ -67,7 +67,7 @@ Item {
           var currentMap = config['map'].length ? config['map'][currentIndex] : config['map']
           var currentKey = Object.keys(currentMap)[0]
           for(var key in config['map']) {
-            listModel.append( { text: key } )
+            listModel.append( { display: key } )
             reverseConfig[config['map'][key]] = key;
           }
         }

diff --git a/src/quickgui/plugin/editor/qgsquickvaluerelation.qml b/src/quickgui/plugin/editor/qgsquickvaluerelation.qml
@@ -36,42 +36,30 @@ Item {
   }
 
   QgsQuick.EditorWidgetComboBox {
-    // Value relation cache map
-    property var currentMap
-    // Reversed to currentMap. It is used to find key (currentValue) according value (currentText)
-    property var reversedMap: ({})
+
     property var currentValue: value
 
     comboStyle: customStyle.fields
-    textRole: 'text'
+    textRole: 'display'
     height: parent.height
-    model: ListModel {
-      id: listModel
+
+    model: QgsQuick.ValueRelationListModel {
+        id: vrModel
     }
 
     Component.onCompleted: {
-      currentMap = QgsQuick.Utils.createValueRelationCache(config)
-      var valueInKeys = false
-      var keys = Object.keys(currentMap)
-      for(var i=0; i< keys.length; i++)
-      {
-        var currentKey = keys[i]
-        if (value == currentKey) valueInKeys = true
-        var valueText = currentMap[currentKey]
-        listModel.append( { text: valueText } )
-        reversedMap[valueText] = currentKey;
-      }
-      model = listModel
-      currentIndex = valueInKeys ? find(currentMap[value]) : -1
+        vrModel.populate(config)
+        currentIndex = vrModel.rowForKey(value);
     }
 
-    onCurrentTextChanged: {
-      valueChanged(reversedMap[currentText], false)
+    // Called when user makes selection in the combo box
+    onCurrentIndexChanged: {
+      valueChanged(vrModel.keyForRow(currentIndex), false)
     }
 
-    // Workaround to get a signal when the value has changed
+    // Called when the same form is used for a different feature
     onCurrentValueChanged: {
-      currentIndex = currentMap ? find(currentMap[value]) : -1
+        currentIndex = vrModel.rowForKey(value);
     }
 
   }

diff --git a/src/quickgui/plugin/qgsquickplugin.cpp b/src/quickgui/plugin/qgsquickplugin.cpp
@@ -46,6 +46,7 @@
 #include "qgsquickscalebarkit.h"
 #include "qgsquicksubmodel.h"
 #include "qgsquickutils.h"
+#include "qgsquickvaluerelationlistmodel.h"
 
 static QObject *_utilsProvider( QQmlEngine *engine, QJSEngine *scriptEngine )
 {
@@ -87,6 +88,7 @@ void QgsQuickPlugin::registerTypes( const char *uri )
   qmlRegisterType< QgsQuickScaleBarKit >( uri, 0, 1, "ScaleBarKit" );
   qmlRegisterType< QgsQuickSubModel >( uri, 0, 1, "SubModel" );
   qmlRegisterType< QgsVectorLayer >( uri, 0, 1, "VectorLayer" );
+  qmlRegisterType< QgsQuickValueRelationListModel > ( uri, 0, 1, "ValueRelationListModel" );
 
   qmlRegisterSingletonType< QgsQuickUtils >( uri, 0, 1, "Utils", _utilsProvider );
 }

diff --git a/src/quickgui/qgsquickvaluerelationlistmodel.cpp b/src/quickgui/qgsquickvaluerelationlistmodel.cpp
@@ -0,0 +1,72 @@
+/***************************************************************************
+  qgsquickvaluerelationlistmodel.cpp
+  --------------------------------------
+  Date                 : March 2020
+  Copyright            : (C) 2020 by Martin Dobias
+  Email                : wonder dot sk at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsquickvaluerelationlistmodel.h"
+
+#include "qgslogger.h"
+
+
+QgsQuickValueRelationListModel::QgsQuickValueRelationListModel( QObject *parent )
+  : QAbstractListModel( parent )
+{
+}
+
+void QgsQuickValueRelationListModel::populate( const QVariantMap &config, const QgsFeature &formFeature )
+{
+  beginResetModel();
+  mCache = QgsValueRelationFieldFormatter::createCache( config, formFeature );
+  endResetModel();
+}
+
+QVariant QgsQuickValueRelationListModel::keyForRow( int row ) const
+{
+  if ( row < 0 || row >= mCache.count() )
+  {
+    QgsDebugMsg( "keyForRow: access outside of range " + QString::number( row ) );
+    return QVariant();
+  }
+  return mCache[row].key;
+}
+
+int QgsQuickValueRelationListModel::rowForKey( const QVariant &key ) const
+{
+  for ( int i = 0; i < mCache.count(); ++i )
+  {
+    if ( mCache[i].key == key )
+      return i;
+  }
+  QgsDebugMsg( "rowForKey: key not found: " + key.toString() );
+  return -1;
+}
+
+int QgsQuickValueRelationListModel::rowCount( const QModelIndex & ) const
+{
+  return mCache.count();
+}
+
+QVariant QgsQuickValueRelationListModel::data( const QModelIndex &index, int role ) const
+{
+  if ( !index.isValid() )
+    return QVariant();
+
+  int row = index.row();
+  if ( row < 0 || row >= mCache.count() )
+    return QVariant();
+
+  if ( role == Qt::DisplayRole )
+    return mCache[row].value;
+
+  return QVariant();
+}
diff --git a/src/quickgui/qgsquickvaluerelationlistmodel.h b/src/quickgui/qgsquickvaluerelationlistmodel.h
@@ -0,0 +1,57 @@
+/***************************************************************************
+  qgsquickvaluerelationlistmodel.h
+  --------------------------------------
+  Date                 : March 2020
+  Copyright            : (C) 2020 by Martin Dobias
+  Email                : wonder dot sk at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSQUICKVALUERELATIONLISTMODEL_H
+#define QGSQUICKVALUERELATIONLISTMODEL_H
+
+#include "qgis_quick.h"
+
+#include <QAbstractListModel>
+
+#include "qgsvaluerelationfieldformatter.h"
+
+/**
+ * \ingroup quick
+ * List model for combo box in Value Relation widget.
+ * The model keeps a list of key-value pairs fetched from a vector layer. "Values" are the human readable
+ * descriptions (QString), "keys" are unique identifiers of items (QVariant).
+ *
+ * \note QML Type: ValueRelationListModel
+ *
+ * \since QGIS 3.14
+ */
+class QUICK_EXPORT QgsQuickValueRelationListModel : public QAbstractListModel
+{
+    Q_OBJECT
+  public:
+    //! Construct an empty list model
+    QgsQuickValueRelationListModel( QObject *parent = nullptr );
+
+    //! Populate the model from vector layer's widget configuration
+    Q_INVOKABLE void populate( const QVariantMap &config, const QgsFeature &formFeature = QgsFeature() );
+
+    //! Returns key for the given rown number (invalid variant if outside of the valid range)
+    Q_INVOKABLE QVariant keyForRow( int row ) const;
+    //! Returns row number
+    Q_INVOKABLE int rowForKey( const QVariant &key ) const;
+
+    int rowCount( const QModelIndex & ) const override;
+    QVariant data( const QModelIndex &index, int role = Qt::DisplayRole ) const override;
+
+  private:
+    QgsValueRelationFieldFormatter::ValueRelationCache mCache;
+};
+
+#endif // QGSQUICKVALUERELATIONLISTMODEL_H