Make it possible to MapItems to rendered under some style layers

Add a MapParamter to specify the default "before" layer for MapItems
that Mapbox GL can render. This can be used for inserting route lines
before labels.

Change-Id: I3ee414ee8af31f38b74c95b3ecc31df6085bed30
Reviewed-by: Paolo Angelelli <paolo.angelelli@qt.io>

8 files changed, 40 insertions, 9 deletions

diff --git a/src/location/doc/src/plugins/mapboxgl.qdoc b/src/location/doc/src/plugins/mapboxgl.qdoc
index a412548e..4084e4c6 100644
--- a/src/location/doc/src/plugins/mapboxgl.qdoc
+++ b/src/location/doc/src/plugins/mapboxgl.qdoc
@@ -128,6 +128,14 @@ The following table lists optional parameters that can be passed to the Mapbox p
     experimental, and it does not support QQuickItem transformations nor stencil
     clipping. It might be also produce rendering artifacts e.g. when adding it
     inside a \l{QtQuick::Flipable}{Flipable} item.
+\row
+    \li mapboxgl.mapping.items.insert_before
+    \li Some map items such as \l{QtLocation::MapPolyline}{MapPolyline},
+    \l{QtLocation::MapPolygon}{MapPolygon} and \l{QtLocation::MapRectangle}{MapRectangle}
+    will be rendered after the topmost \l {https://www.mapbox.com/mapbox-gl-js/style-spec/#layers}{layer}
+    of the style. With this parameter set, the map items will be rendered \b before the layer ID
+    specified, unless the layer is not present on the current style, which will fallback
+    to the default behavior. This parameter can be used to display route lines under labels.
 \endtable
 
 \section2 Optional map parameters
@@ -166,7 +174,7 @@ replacing the dash with camel case for technical reasons (i.e. \b line-cap will
     \li layer
     \li Adds a new \l {https://www.mapbox.com/mapbox-gl-js/style-spec/#layers}{style layer} to the map. On a Mapbox GL map,
     layers are used in styles for adding styling rules to specific subsets of data. A layer will contain a reference to the
-    data for which they are defining a style.
+    data for which they are defining a style. Use the \b before attribute to insert a layer before an existing layer.
 \row
     \li paint
     \li Defines how a layer will be painted. \l {https://www.mapbox.com/mapbox-gl-js/style-spec/#layer-paint}{Paint} properties
@@ -218,6 +226,10 @@ Map {
         property var name: "route"
         property var layerType: "line"
         property var source: "routeSource"
+
+        // Draw under the first road label layer
+        // of the mapbox-streets style.
+        property var before: "road-label-small"
     }
 
     MapParameter {
diff --git a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.cpp b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.cpp
index 563c84f2..82378f0a 100644
--- a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.cpp
+++ b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.cpp
@@ -210,7 +210,7 @@ void QGeoMapMapboxGLPrivate::addMapItem(QDeclarativeGeoMapItemBase *item)
 
     QObject::connect(item, &QDeclarativeGeoMapItemBase::mapItemOpacityChanged, q, &QGeoMapMapboxGL::onMapItemPropertyChanged);
 
-    m_styleChanges << QMapboxGLStyleChange::addMapItem(item);
+    m_styleChanges << QMapboxGLStyleChange::addMapItem(item, m_mapItemsBefore);
 
     emit q->sgNodeChanged();
 }
@@ -342,6 +342,12 @@ void QGeoMapMapboxGL::setUseFBO(bool useFBO)
     d->m_useFBO = useFBO;
 }
 
+void QGeoMapMapboxGL::setMapItemsBefore(const QString &before)
+{
+    Q_D(QGeoMapMapboxGL);
+    d->m_mapItemsBefore = before;
+}
+
 QSGNode *QGeoMapMapboxGL::updateSceneGraph(QSGNode *oldNode, QQuickWindow *window)
 {
     Q_D(QGeoMapMapboxGL);
@@ -362,7 +368,7 @@ void QGeoMapMapboxGL::onMapChanged(QMapboxGL::MapChange change)
             d->m_styleChanges << QMapboxGLStyleChange::addMapParameter(param);
 
         for (QDeclarativeGeoMapItemBase *item : d->m_mapItems)
-            d->m_styleChanges << QMapboxGLStyleChange::addMapItem(item);
+            d->m_styleChanges << QMapboxGLStyleChange::addMapItem(item, d->m_mapItemsBefore);
     }
 }
 
diff --git a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.h b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.h
index 56b97e99..73cfd75a 100644
--- a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.h
+++ b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl.h
@@ -56,6 +56,7 @@ public:
     QString copyrightsStyleSheet() const Q_DECL_OVERRIDE;
     void setMapboxGLSettings(const QMapboxGLSettings &);
     void setUseFBO(bool);
+    void setMapItemsBefore(const QString &);
 
 private Q_SLOTS:
     // QMapboxGL
diff --git a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl_p.h b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl_p.h
index 15e5d167..598c9078 100644
--- a/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl_p.h
+++ b/src/plugins/geoservices/mapboxgl/qgeomapmapboxgl_p.h
@@ -79,6 +79,7 @@ public:
     QMapboxGLSettings m_settings;
     bool m_useFBO = true;
     bool m_developmentMode = false;
+    QString m_mapItemsBefore;
 
     QTimer m_refresh;
     bool m_shouldRefresh = true;
diff --git a/src/plugins/geoservices/mapboxgl/qgeomappingmanagerenginemapboxgl.cpp b/src/plugins/geoservices/mapboxgl/qgeomappingmanagerenginemapboxgl.cpp
index 0535bf96..211c0bba 100644
--- a/src/plugins/geoservices/mapboxgl/qgeomappingmanagerenginemapboxgl.cpp
+++ b/src/plugins/geoservices/mapboxgl/qgeomappingmanagerenginemapboxgl.cpp
@@ -138,6 +138,10 @@ QGeoMappingManagerEngineMapboxGL::QGeoMappingManagerEngineMapboxGL(const QVarian
         m_useFBO = parameters.value(QStringLiteral("mapboxgl.mapping.use_fbo")).toBool();
     }
 
+    if (parameters.contains(QStringLiteral("mapboxgl.mapping.items.insert_before"))) {
+        m_mapItemsBefore = parameters.value(QStringLiteral("mapboxgl.mapping.items.insert_before")).toString();
+    }
+
     engineInitialized();
 }
 
@@ -150,6 +154,7 @@ QGeoMap *QGeoMappingManagerEngineMapboxGL::createMap()
     QGeoMapMapboxGL* map = new QGeoMapMapboxGL(this, 0);
     map->setMapboxGLSettings(m_settings);
     map->setUseFBO(m_useFBO);
+    map->setMapItemsBefore(m_mapItemsBefore);
 
     return map;
 }
diff --git a/src/plugins/geoservices/mapboxgl/qgeomappingmanagerenginemapboxgl.h b/src/plugins/geoservices/mapboxgl/qgeomappingmanagerenginemapboxgl.h
index c5923cda..44096e60 100644
--- a/src/plugins/geoservices/mapboxgl/qgeomappingmanagerenginemapboxgl.h
+++ b/src/plugins/geoservices/mapboxgl/qgeomappingmanagerenginemapboxgl.h
@@ -59,6 +59,7 @@ public:
 private:
     QMapboxGLSettings m_settings;
     bool m_useFBO = true;
+    QString m_mapItemsBefore;
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/geoservices/mapboxgl/qmapboxglstylechange.cpp b/src/plugins/geoservices/mapboxgl/qmapboxglstylechange.cpp
index eccc64b8..8229b784 100644
--- a/src/plugins/geoservices/mapboxgl/qmapboxglstylechange.cpp
+++ b/src/plugins/geoservices/mapboxgl/qmapboxglstylechange.cpp
@@ -175,7 +175,7 @@ QList<QSharedPointer<QMapboxGLStyleChange>> QMapboxGLStyleChange::addMapParamete
     return changes;
 }
 
-QList<QSharedPointer<QMapboxGLStyleChange>> QMapboxGLStyleChange::addMapItem(QDeclarativeGeoMapItemBase *item)
+QList<QSharedPointer<QMapboxGLStyleChange>> QMapboxGLStyleChange::addMapItem(QDeclarativeGeoMapItemBase *item, const QString &before)
 {
     QList<QSharedPointer<QMapboxGLStyleChange>> changes;
 
@@ -191,7 +191,7 @@ QList<QSharedPointer<QMapboxGLStyleChange>> QMapboxGLStyleChange::addMapItem(QDe
 
     QMapbox::Feature feature = featureFromMapItem(item);
 
-    changes << QMapboxGLStyleAddLayer::fromFeature(feature);
+    changes << QMapboxGLStyleAddLayer::fromFeature(feature, before);
     changes << QMapboxGLStyleAddSource::fromFeature(feature);
     changes << QMapboxGLStyleSetPaintProperty::fromMapItem(item);
     changes << QMapboxGLStyleSetLayoutProperty::fromMapItem(item);
@@ -390,7 +390,7 @@ QList<QSharedPointer<QMapboxGLStyleChange>> QMapboxGLStyleSetPaintProperty::from
 
 void QMapboxGLStyleAddLayer::apply(QMapboxGL *map)
 {
-    map->addLayer(m_params);
+    map->addLayer(m_params, m_before);
 }
 
 QSharedPointer<QMapboxGLStyleChange> QMapboxGLStyleAddLayer::fromMapParameter(QGeoMapParameter *param)
@@ -406,10 +406,12 @@ QSharedPointer<QMapboxGLStyleChange> QMapboxGLStyleAddLayer::fromMapParameter(QG
         layer->m_params[QStringLiteral("source-layer")] = param->property("sourceLayer");
     }
 
+    layer->m_before = param->property("before").toString();
+
     return QSharedPointer<QMapboxGLStyleChange>(layer);
 }
 
-QSharedPointer<QMapboxGLStyleChange> QMapboxGLStyleAddLayer::fromFeature(const QMapbox::Feature &feature)
+QSharedPointer<QMapboxGLStyleChange> QMapboxGLStyleAddLayer::fromFeature(const QMapbox::Feature &feature, const QString &before)
 {
     auto layer = new QMapboxGLStyleAddLayer();
     layer->m_params[QStringLiteral("id")] = feature.id;
@@ -427,6 +429,8 @@ QSharedPointer<QMapboxGLStyleChange> QMapboxGLStyleAddLayer::fromFeature(const Q
         break;
     }
 
+    layer->m_before = before;
+
     return QSharedPointer<QMapboxGLStyleChange>(layer);
 }
 
diff --git a/src/plugins/geoservices/mapboxgl/qmapboxglstylechange_p.h b/src/plugins/geoservices/mapboxgl/qmapboxglstylechange_p.h
index a380660b..9164591a 100644
--- a/src/plugins/geoservices/mapboxgl/qmapboxglstylechange_p.h
+++ b/src/plugins/geoservices/mapboxgl/qmapboxglstylechange_p.h
@@ -58,7 +58,7 @@ public:
     virtual ~QMapboxGLStyleChange() = default;
 
     static QList<QSharedPointer<QMapboxGLStyleChange>> addMapParameter(QGeoMapParameter *);
-    static QList<QSharedPointer<QMapboxGLStyleChange>> addMapItem(QDeclarativeGeoMapItemBase *);
+    static QList<QSharedPointer<QMapboxGLStyleChange>> addMapItem(QDeclarativeGeoMapItemBase *, const QString &before);
     static QList<QSharedPointer<QMapboxGLStyleChange>> removeMapItem(QDeclarativeGeoMapItemBase *);
 
     virtual void apply(QMapboxGL *map) = 0;
@@ -109,7 +109,7 @@ class QMapboxGLStyleAddLayer : public QMapboxGLStyleChange
 {
 public:
     static QSharedPointer<QMapboxGLStyleChange> fromMapParameter(QGeoMapParameter *);
-    static QSharedPointer<QMapboxGLStyleChange> fromFeature(const QMapbox::Feature &feature);
+    static QSharedPointer<QMapboxGLStyleChange> fromFeature(const QMapbox::Feature &feature, const QString &before);
 
     void apply(QMapboxGL *map) Q_DECL_OVERRIDE;
 
@@ -117,6 +117,7 @@ private:
     QMapboxGLStyleAddLayer() = default;
 
     QVariantMap m_params;
+    QString m_before;
 };
 
 class QMapboxGLStyleRemoveLayer : public QMapboxGLStyleChange