Add unique values cpp model

app/CMakeLists.txt

@@ -56,6 +56,7 @@ set(MM_SRCS
     featurelayerpair.cpp
     featuresmodel.cpp
     fieldsmodel.cpp
+    filter/uniquevaluesfiltermodel.cpp
     filtercontroller.cpp
     guidelinecontroller.cpp
     hapticsmodel.cpp
@@ -148,6 +149,7 @@ set(MM_HDRS
     featurelayerpair.h
     featuresmodel.h
     fieldsmodel.h
+    filter/uniquevaluesfiltermodel.h
     filtercontroller.h
     guidelinecontroller.h
     hapticsmodel.h
@@ -320,6 +322,7 @@ target_include_directories(
   MerginMaps
   PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/
          ${CMAKE_CURRENT_SOURCE_DIR}/attributes
+         ${CMAKE_CURRENT_SOURCE_DIR}/filter
          ${CMAKE_CURRENT_SOURCE_DIR}/map
          ${CMAKE_CURRENT_SOURCE_DIR}/layer
          ${CMAKE_CURRENT_SOURCE_DIR}/maptools

app/attributes/attributeformmodel.cpp

@@ -178,7 +178,7 @@ bool AttributeFormModel::setData( const QModelIndex &index, const QVariant &valu
     case AttributeValue:
     {
       const FormItem *item = mController->formItem( uuid );
-      //if ( mController->formValue( item->fieldIndex() ) == value )
+
       if ( item->rawValue() == value )
       {
         return false;

app/filter/uniquevaluesfiltermodel.cpp

@@ -0,0 +1,141 @@
+/***************************************************************************
+ *                                                                         *
+ *   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 "uniquevaluesfiltermodel.h"
+#include "coreutils.h"
+
+#include <qgsproject.h>
+#include <qgsvectorlayer.h>
+#include <QtConcurrentRun>
+
+
+UniqueValuesFilterModel::UniqueValuesFilterModel( QObject *parent )
+  : QAbstractListModel( parent )
+{
+  // <TODO> remove me once this class is used! :)
+  const QMap<QString, QgsMapLayer *> layers = QgsProject::instance()->mapLayers();
+  for ( auto it = layers.constBegin(); it != layers.constEnd(); ++it )
+  {
+    QgsVectorLayer *vectorLayer = qobject_cast<QgsVectorLayer *>( it.value() );
+    if ( vectorLayer )
+    {
+      setLayer( vectorLayer );
+      setFieldName( "fid" );
+      break;
+    }
+  }
+  // </TODO>
+
+  connect( &mResultWatcher, &QFutureWatcher<QVariantList>::finished, this, &UniqueValuesFilterModel::onLoadingFinished );
+}
+
+int UniqueValuesFilterModel::rowCount( const QModelIndex &parent ) const
+{
+  Q_UNUSED( parent )
+  return mItems.size();
+}
+
+QVariant UniqueValuesFilterModel::data( const QModelIndex &index, int role ) const
+{
+  if ( !index.isValid() || index.row() >= mItems.size() )
+    return {};
+
+  switch ( role )
+  {
+    case Qt::DisplayRole:
+      return mItems.at( index.row() );
+    default:
+      return {};
+  }
+}
+
+QgsVectorLayer *UniqueValuesFilterModel::layer() const
+{
+  return mLayer;
+}
+
+void UniqueValuesFilterModel::setLayer( QgsVectorLayer *layer )
+{
+  if ( mLayer == layer )
+    return;
+
+  mLayer = layer;
+  emit layerChanged();
+}
+
+QString UniqueValuesFilterModel::fieldName() const
+{
+  return mFieldName;
+}
+
+void UniqueValuesFilterModel::setFieldName( const QString &fieldName )
+{
+  if ( mFieldName == fieldName )
+    return;
+
+  mFieldName = fieldName;
+  emit fieldNameChanged();
+}
+
+void UniqueValuesFilterModel::populate()
+{
+  if ( !mLayer || mFieldName.isEmpty() )
+    return;
+
+  int fieldIndex = mLayer->fields().lookupField( mFieldName );
+  if ( fieldIndex < 0 )
+  {
+    CoreUtils::log( QStringLiteral( "Filtering" ), QStringLiteral( "Error, field %1 could not be found, dropdown filter won't work." ).arg( mFieldName ) );
+    return;
+  }
+
+  if ( mItems.size() > 0 ) return;
+
+  if ( mResultWatcher.isRunning() ) return;
+
+  QgsVectorLayer *layerClone = mLayer->clone();
+
+  mResultWatcher.setFuture( QtConcurrent::run( &UniqueValuesFilterModel::loadUniqueValues, this, layerClone, fieldIndex ) );
+}
+
+QVariantList UniqueValuesFilterModel::loadUniqueValues( QgsVectorLayer *layer, int fieldIndex )
+{
+  std::unique_ptr<QgsVectorLayer> l( layer );
+
+  const QSet<QVariant> uniqueValues = l->uniqueValues( fieldIndex, 1000000 );
+
+  QVariantList results;
+
+  results.reserve( uniqueValues.size() );
+
+  for ( const QVariant &v : uniqueValues )
+  {
+    results.append( v );
+  }
+
+  std::sort( results.begin(), results.end(), []( const QVariant & a, const QVariant & b )
+  {
+    return a.toString() < b.toString();
+  } );
+
+  return results;
+}
+
+void UniqueValuesFilterModel::onLoadingFinished()
+{
+  beginResetModel();
+
+  mItems.clear();
+  mItems = mResultWatcher.result();
+
+  // TODO: do we need boolean to indicate if the model is loading?
+  // TODO: measure how long it takes to move results from future result to mItems ~ there might be a way to avoid the copy
+
+  endResetModel();
+}

app/filter/uniquevaluesfiltermodel.h

@@ -0,0 +1,60 @@
+/***************************************************************************
+ *                                                                         *
+ *   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 UNIQUEVALUESFILTERMODEL_H
+#define UNIQUEVALUESFILTERMODEL_H
+
+#include <QAbstractListModel>
+#include <QFutureWatcher>
+#include <QtQml/qqmlregistration.h>
+
+class QgsVectorLayer;
+
+// This model loads unique values from the selected layer+field and exposes them via Qt::DisplayRole
+class UniqueValuesFilterModel : public QAbstractListModel
+{
+    Q_OBJECT
+    QML_ELEMENT
+
+    Q_PROPERTY( QgsVectorLayer *layer READ layer WRITE setLayer NOTIFY layerChanged )
+    Q_PROPERTY( QString fieldName READ fieldName WRITE setFieldName NOTIFY fieldNameChanged )
+
+  public:
+    explicit UniqueValuesFilterModel( QObject *parent = nullptr );
+    ~UniqueValuesFilterModel() override = default;
+
+    int rowCount( const QModelIndex &parent = QModelIndex() ) const override;
+    QVariant data( const QModelIndex &index, int role = Qt::DisplayRole ) const override;
+
+    QgsVectorLayer *layer() const;
+    void setLayer( QgsVectorLayer *layer );
+
+    QString fieldName() const;
+    void setFieldName( const QString &fieldName );
+
+    Q_INVOKABLE void populate();
+
+  signals:
+    void layerChanged();
+    void fieldNameChanged();
+
+  public slots:
+    void onLoadingFinished();
+
+  private:
+    QVariantList loadUniqueValues( QgsVectorLayer *layer, int fieldIndex );
+
+    QgsVectorLayer *mLayer = nullptr;
+    QString mFieldName;
+
+    QVariantList mItems;
+    QFutureWatcher<QVariantList> mResultWatcher;
+};
+
+#endif // UNIQUEVALUESFILTERMODEL_H