Map reference scale

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Sample viewer app

Set the map's reference scale and which feature layers should honor the reference scale.

screenshot

Use case

Setting a reference scale on a Map fixes the size of symbols and text to the desired height and width at that scale. As you zoom in and out, symbols and text will increase or decrease in size accordingly. When no reference scale is set, symbol and text sizes remain the same size relative to the MapView.

Map annotations are typically only relevant at certain scales. For instance, annotations to a map showing a construction site are only relevant at that construction site's scale. So, when the map is zoomed out that information shouldn't scale with the MapView, but should instead remain scaled with the Map.

How to use the sample

  • Use the drop box at the top to set the map's reference scale (1:500,000 1:250,000 1:100,000 1:50,000).
  • Click the button to set the map scale to the reference scale.
  • Use the menu checkboxes in the layer menu to set which feature layers should honor the reference scale.

How it works

  1. Get and set the reference scale property on the Map object.
  2. Get and set the scale symbols property on each individual FeatureLayer object.

Relevant API

  • Map
  • FeatureLayer

Additional information

The map reference scale should normally be set by the map's author and not exposed to the end user like it is in this sample.

Tags

map, reference scale, scene

Sample Code

MapReferenceScale.cppMapReferenceScale.cppMapReferenceScale.hMapReferenceScale.qml
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// [WriteFile Name=MapReferenceScale, Category=Maps]
// [Legal]
// Copyright 2019 Esri.

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0

// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// [Legal]

#ifdef PCH_BUILD
#include "pch.hpp"
#endif // PCH_BUILD

#include "MapReferenceScale.h"

#include "Portal.h"
#include "PortalItem.h"
#include "Map.h"
#include "Layer.h"
#include "FeatureLayer.h"
#include "LayerListModel.h"
#include "MapQuickView.h"


using namespace Esri::ArcGISRuntime;


MapReferenceScale::MapReferenceScale(QObject* parent /* = nullptr */):
  QObject(parent),
  m_portal(new Portal(this)),
  m_portalItem(new PortalItem(m_portal, "3953413f3bd34e53a42bf70f2937a408", this))
{
  m_map = new Map(m_portalItem, this);

  // Once map is loaded set FeatureLayer list model
  connect(m_map, &Map::doneLoading, this, [this](Error loadError)
  {
    if (!loadError.isEmpty())
      return;

    m_layerInfoListModel = m_map->operationalLayers();
    emit layerInfoListModelChanged();
    emit currentMapScaleChanged();

    connect(m_mapView, &MapQuickView::mapScaleChanged, this, [this]()
    {
      emit currentMapScaleChanged();
    });
  });
}

MapReferenceScale::~MapReferenceScale() = default;

void MapReferenceScale::init()
{
  // Register the map view for QML
  qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
  qmlRegisterType<MapReferenceScale>("Esri.Samples", 1, 0, "MapReferenceScaleSample");
  qmlRegisterUncreatableType<QAbstractListModel>("Esri.Samples", 1, 0, "AbstractListModel", "AbstractListModel is uncreateable");
}


double MapReferenceScale::currentMapScale() const
{
  if (!m_mapView)
    return 0.0;

  return m_mapView->mapScale();
}

void MapReferenceScale::setCurrentMapScale(double scale)
{
  if(!m_map)
    return;

  m_map->setReferenceScale(scale);
}

void MapReferenceScale::setMapScaleToReferenceScale(double scale)
{
  if(m_mapView)
    m_mapView->setViewpointScale(scale);
}

void MapReferenceScale::featureLayerScaleSymbols(const QString& layerName, bool checkedStatus)
{
  if(m_layerInfoListModel)
  {
    for(Layer* layer : *static_cast<LayerListModel*>(m_layerInfoListModel))
    {
      if(layer->name() == layerName)
      {
        FeatureLayer* featureLayer = static_cast<FeatureLayer*>(layer);
        if(featureLayer)
          featureLayer->setScaleSymbols(checkedStatus);
      }
    }
  }
}

MapQuickView* MapReferenceScale::mapView() const
{
  return m_mapView;
}

// Set the view (created in QML)
void MapReferenceScale::setMapView(MapQuickView* mapView)
{
  if (!mapView || mapView == m_mapView)
    return;

  m_mapView = mapView;
  m_mapView->setMap(m_map);

  emit mapViewChanged();
}

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