apply map transform directly in the feature highligh c++ code

Author: PeterPetrik

src/quickgui/qgsquickfeaturehighlight.cpp

@@ -28,7 +28,10 @@ QgsQuickFeatureHighlight::QgsQuickFeatureHighlight( QQuickItem *parent )
   setFlags( QQuickItem::ItemHasContents );
   setAntialiasing( true );
 
-  connect( this, &QgsQuickFeatureHighlight::mapSettingsChanged, this, &QgsQuickFeatureHighlight::markDirty );
+  // transform to device coords
+  mTransform.appendToItem(this);
+
+  connect( this, &QgsQuickFeatureHighlight::mapSettingsChanged, this, &QgsQuickFeatureHighlight::onMapSettingsChanged );
   connect( this, &QgsQuickFeatureHighlight::featureLayerPairChanged, this, &QgsQuickFeatureHighlight::markDirty );
   connect( this, &QgsQuickFeatureHighlight::colorChanged, this, &QgsQuickFeatureHighlight::markDirty );
   connect( this, &QgsQuickFeatureHighlight::widthChanged, this, &QgsQuickFeatureHighlight::markDirty );
@@ -40,6 +43,12 @@ void QgsQuickFeatureHighlight::markDirty()
   update();
 }
 
+void QgsQuickFeatureHighlight::onMapSettingsChanged()
+{
+  mTransform.setMapSettings(mMapSettings);
+  markDirty();
+}
+
 QSGNode *QgsQuickFeatureHighlight::updatePaintNode( QSGNode *n, QQuickItem::UpdatePaintNodeData * )
 {
   if ( !mDirty || !mMapSettings || !mFeatureLayerPair.isValid() )

src/quickgui/qgsquickfeaturehighlight.h

@@ -20,6 +20,7 @@
 
 #include "qgsquickfeaturelayerpair.h"
 #include "qgis_quick.h"
+#include "qgsquickmaptransform.h"
 
 class QgsQuickMapSettings;
 
@@ -28,9 +29,10 @@ class QgsQuickMapSettings;
  *
  * Creates map highlights for a geometry provided by a FeatureModel.
  *
- * The highlights are compatible with the QtQuick scene graph.
+ * The highlights are compatible with the QtQuick scene graph and
+ * can be direcly shown on map canvas
  *
- * \note QML Type: FeatureModelHighlight
+ * \note QML Type: FeatureHighlight
  *
  * \since QGIS 3.4
  */
@@ -81,6 +83,7 @@ class QUICK_EXPORT QgsQuickFeatureHighlight : public QQuickItem
 
   private slots:
     void markDirty();
+    void onMapSettingsChanged();
 
   private:
     QSGNode *updatePaintNode( QSGNode *n, UpdatePaintNodeData * ) override;
@@ -90,6 +93,7 @@ class QUICK_EXPORT QgsQuickFeatureHighlight : public QQuickItem
     float mWidth = 20;
     QgsQuickFeatureLayerPair mFeatureLayerPair;
     QgsQuickMapSettings *mMapSettings = nullptr; // not owned
+    QgsQuickMapTransform mTransform;
 };
 
 #endif // QGSQUICKFEATUREHIGHLIGHT_H

src/quickgui/qgsquickmaptransform.cpp

@@ -46,10 +46,11 @@ void QgsQuickMapTransform::setMapSettings( QgsQuickMapSettings *mapSettings )
 void QgsQuickMapTransform::updateMatrix()
 {
   QMatrix4x4 matrix;
-  float scaleFactor = 1 / mMapSettings->mapUnitsPerPixel();
+  float scaleFactor = static_cast<float>(1.0 / mMapSettings->mapUnitsPerPixel());
 
   matrix.scale( scaleFactor, -scaleFactor );
-  matrix.translate( -mMapSettings->visibleExtent().xMinimum(), -mMapSettings->visibleExtent().yMaximum() );
+  matrix.translate( static_cast<float>(-mMapSettings->visibleExtent().xMinimum( )),
+                    static_cast<float>(-mMapSettings->visibleExtent().yMaximum() ));
 
   mMatrix = matrix;
   update();

src/quickgui/qgsquickmaptransform.h

@@ -25,10 +25,10 @@ class QgsQuickMapSettings;
 
 /**
  * \ingroup quick
- * The QgsQuickMapTransform is transformation that can be attached to any QQuickItem. Transformation scales and translates
- * Item based on the current QgsQuickMapSettings settings.
+ * The QgsQuickMapTransform is transformation that can be attached to any QQuickItem.
  *
- * For example it can be used on QgsQuickFeatureHighlight to place it correctly on the map canvas.
+ * If the item is based on the map coordinates, QgsQuickMapTransform will
+ * transform it to the device coordintes based on the attached map settings.
  *
  * \note QML Type: MapTransform
  *

tests/src/quickgui/app/main.qml

@@ -44,19 +44,12 @@ ApplicationWindow {
     }
   }
 
-  Item {
+  QgsQuick.FeatureHighlight {
     anchors.fill: mapCanvas
-    transform: QgsQuick.MapTransform {
-      mapSettings: mapCanvas.mapSettings
-    }
-
-    QgsQuick.FeatureHighlight {
-      id: highlight
-      color: "red"
-      mapSettings: mapCanvas.mapSettings
-    }
-
-    z: 1   // make sure items from here are on top of the Z-order
+    id: highlight
+    color: "red"
+    mapSettings: mapCanvas.mapSettings
+    z: 1
   }
 
   Drawer {