Add layer resolver

src/core/CMakeLists.txt

@@ -21,6 +21,7 @@ SET(QFIELD_CORE_SRCS
   identifytool.cpp
   layertreemapcanvasbridge.cpp
   layertreemodel.cpp
+  layerresolver.cpp
   legendimageprovider.cpp
   linepolygonhighlight.cpp
   locatormodelsuperbridge.cpp
@@ -94,6 +95,7 @@ SET(QFIELD_CORE_HDRS
   identifytool.h
   layertreemapcanvasbridge.h
   layertreemodel.h
+  layerresolver.h
   legendimageprovider.h
   linepolygonhighlight.h
   locatormodelsuperbridge.h

src/core/layerresolver.cpp

@@ -0,0 +1,128 @@
+/***************************************************************************
+                            layerresolver.cpp
+
+                              -------------------
+              begin                : January 2021
+              copyright            : (C) 2011 by Matthias Kuhn
+              email                : matthias@opengis.ch
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   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 "layerresolver.h"
+#include <qgsvectorlayerref.h>
+
+LayerResolver::LayerResolver( QObject *parent )
+  : QObject( parent )
+{
+
+}
+
+void LayerResolver::resolve()
+{
+  if ( !mProject )
+  {
+    setLayer( nullptr );
+    return;
+  }
+
+  QgsVectorLayerRef ref { mLayerId,
+                          mLayerName,
+                          mLayerSource,
+                          mLayerProviderName };
+  setLayer( ref.resolveByIdOrNameOnly( mProject ) );
+}
+
+QString LayerResolver::layerId() const
+{
+  return mLayerId;
+}
+
+void LayerResolver::setLayerId( const QString &layerId )
+{
+  if ( mLayerId == layerId )
+    return;
+
+  mLayerId = layerId;
+  resolve();
+  emit layerIdChanged();
+}
+
+QString LayerResolver::layerName() const
+{
+  return mLayerName;
+}
+
+void LayerResolver::setLayerName( const QString &layerName )
+{
+  if ( mLayerName == layerName )
+    return;
+
+  mLayerName = layerName;
+  resolve();
+  emit layerNameChanged();
+}
+
+QString LayerResolver::layerSource() const
+{
+  return mLayerSource;
+}
+
+void LayerResolver::setLayerSource( const QString &layerSource )
+{
+  if ( mLayerSource == layerSource )
+    return;
+
+  mLayerSource = layerSource;
+  emit layerSourceChanged();
+}
+
+QString LayerResolver::layerProviderName() const
+{
+  return mLayerProviderName;
+}
+
+void LayerResolver::setLayerProviderName( const QString &layerProviderName )
+{
+  if ( mLayerProviderName == layerProviderName )
+    return;
+
+  mLayerProviderName = layerProviderName;
+  resolve();
+  emit layerProviderNameChanged();
+}
+
+QgsVectorLayer *LayerResolver::currentLayer() const
+{
+  return mLayer;
+}
+
+void LayerResolver::setLayer( QgsVectorLayer *layer )
+{
+  if ( mLayer == layer )
+    return;
+
+  mLayer = layer;
+  emit currentLayerChanged();
+}
+
+QgsProject *LayerResolver::project() const
+{
+  return mProject;
+}
+
+void LayerResolver::setProject( QgsProject *project )
+{
+  if ( project == mProject )
+    return;
+
+  mProject = project;
+  resolve();
+  emit projectChanged();
+}

src/core/layerresolver.h

@@ -0,0 +1,104 @@
+/***************************************************************************
+                            layerresolver.h
+
+                              -------------------
+              begin                : January 2021
+              copyright            : (C) 2011 by Matthias Kuhn
+              email                : matthias@opengis.ch
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   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 LAYERRESOLVER_H
+#define LAYERRESOLVER_H
+
+#include <QObject>
+
+class QgsVectorLayer;
+class QgsProject;
+
+/**
+ * Helper class to resolve layers by id, name, source and provider.
+ */
+class LayerResolver : public QObject
+{
+    Q_OBJECT
+
+    /**
+     * The layer id to resolve
+     */
+    Q_PROPERTY( QString layerId READ layerId WRITE setLayerId NOTIFY layerIdChanged )
+
+    /**
+     * The layer name to resolve
+     */
+    Q_PROPERTY( QString layerName READ layerName WRITE setLayerName NOTIFY layerNameChanged )
+
+    /**
+     * The layer source to resolve
+     */
+    Q_PROPERTY( QString layerSource READ layerSource WRITE setLayerSource NOTIFY layerSourceChanged )
+
+    /**
+     * The layer provider name to resolve
+     */
+    Q_PROPERTY( QString layerProviderName READ layerProviderName WRITE setLayerProviderName NOTIFY layerProviderNameChanged )
+
+    /**
+     * The qgis project from which layers will be acquired
+     */
+    Q_PROPERTY( QgsProject *project READ project WRITE setProject NOTIFY projectChanged )
+
+    /**
+     * Contains the layer after a successful resolving process
+     */
+    Q_PROPERTY( QgsVectorLayer *currentLayer READ currentLayer NOTIFY currentLayerChanged )
+
+  public:
+    explicit LayerResolver( QObject *parent = nullptr );
+
+    void resolve();
+
+    QString layerId() const;
+    void setLayerId( const QString &layerId );
+
+    QString layerName() const;
+    void setLayerName( const QString &layerName );
+
+    QString layerSource() const;
+    void setLayerSource( const QString &layerSource );
+
+    QString layerProviderName() const;
+    void setLayerProviderName( const QString &layerProviderName );
+
+    QgsVectorLayer *currentLayer() const;
+
+    QgsProject *project() const;
+    void setProject( QgsProject *project );
+
+  signals:
+    void layerIdChanged();
+    void layerNameChanged();
+    void layerSourceChanged();
+    void layerProviderNameChanged();
+    void currentLayerChanged();
+    void projectChanged();
+
+  private:
+    void setLayer( QgsVectorLayer *layer );
+
+    QString mLayerId;
+    QString mLayerName;
+    QString mLayerSource;
+    QString mLayerProviderName;
+    QgsProject *mProject = nullptr;
+    QgsVectorLayer *mLayer = nullptr;
+};
+
+#endif // LAYERRESOLVER_H

src/core/qgismobileapp.cpp

@@ -115,6 +115,7 @@
 #include "bluetoothdevicemodel.h"
 #include "gnsspositioninformation.h"
 #include "changelogcontents.h"
+#include "layerresolver.h"
 
 #define QUOTE(string) _QUOTE(string)
 #define _QUOTE(string) #string
@@ -345,6 +346,7 @@ void QgisMobileapp::initDeclarative()
   qmlRegisterType<BluetoothDeviceModel>( "org.qfield", 1, 0, "BluetoothDeviceModel" );
   qmlRegisterType<BluetoothReceiver>( "org.qfield", 1, 0, "BluetoothReceiver" );
   qmlRegisterType<ChangelogContents>( "org.qfield", 1, 0, "ChangelogContents" );
+  qmlRegisterType<LayerResolver>( "org.qfield", 1, 0, "LayerResolver" );
 
   qRegisterMetaType<GnssPositionInformation>( "GnssPositionInformation" );
 

src/qml/editorwidgets/ValueRelation.qml

@@ -17,6 +17,16 @@ Item {
   height: Number(config['AllowMulti']) !== 1 ? valueRelationCombobox.height : valueRelationList.height
   enabled: true
 
+  LayerResolver {
+      id: layerResolver
+
+      layerId: config['Layer']
+      layerName: config['LayerName']
+      layerSource: config['LayerSource']
+      layerProviderName: config['LayerProviderName']
+      project: qgisProject
+  }
+
   RelationCombobox {
     id: valueRelationCombobox
 
@@ -32,7 +42,7 @@ Item {
       attributeField: field
       //passing "" instead of undefined, so the model is cleared on adding new features
       attributeValue: value !== undefined ? value : ""
-      currentLayer: qgisProject.mapLayer(config['Layer'])
+      currentLayer: layerResolver.currentLayer
       currentFormFeature: currentFeature
       keyField: config['Key']
       displayValueField: config['Value']
@@ -65,7 +75,7 @@ Item {
         attributeField: field
         //passing "" instead of undefined, so the model is cleared on adding new features
         attributeValue: value !== undefined ? value : ""
-        currentLayer: qgisProject.mapLayer(config['Layer'])
+        currentLayer: layerResolver.currentLayer
         currentFormFeature: currentFeature
         keyField: config['Key']
         displayValueField: config['Value']