Marble/GeoData/PointerVsImplicitShare

Implicit sharing and storing objects as value is very reasonable for basic data as QStrings, but there are reasonable doubts regarding Placemarks and other GeoData. There are some possibilities:

• Don't use implicit sharing at all and store all objects on the heap with a pointer to it.
• Use implicit sharing and storing as value for GeoDataCoordinates only.
• Use implicit sharing and storing as value for all GeoData classes.

To find out which is the wisest I try to look at every single class: (please add your thoughts here)

Base data

• GeoDataCoordinates This one is quite simple. It is not more than a QPoint in GeoCoordinates. This should stay implicilty shared.
• GeoDataLatLonBox (GeoDataObject) It seems to nothing more than a QRect for GeoCoordinates. I'm not sure if it must be derived from GeoDataObject
  • GeoDataLatLonAltBox same for this
• GeoDataAccuracy Should be base data => value
• GeoDataLod
• GeoDataRegion I'm not sure if it belongs into this group ...

Geometric structures

• GeoDataGeometry The base class for all geometric. We could want a pointer for this, so using it as data may not be the right way.
  • GeoDataPoint This one uses multiple inheritance (GeoDataCoordinates). I don't think that this is semantically correct.
  • GeoDataLineString
    • GeoDataLinearRing
  • GeoDataMultiGeometry
  • GeoDataPolygon

Features

• GeoDataFeature These should be pointered, so GeoGraphicsItems could refer to them and change them easily.
  • GeoDataFeature
  • GeoDataContainer
    • GeoDataFolder (by the way, this is an object which probably wouldn't need a GeoGraphics representation)
    • GeoDataDocument (GeoDocument)

views

• GeoDataAbstractView It's nothing more than a view, this could stay implicitly shared.
  • GeoDataLookAt Same for this as this is a child.

styles

• GeoDataColorStyle
  • GeoDataIconStyle
  • GeoDataLabelStyle
  • GeoDataLineStyle
  • GeoDataPolyStyle
• GeoDataStyleSelector
  • GeoDataStyle
  • GeoDataStyleMap (QMap<QString, QString>)

• GeoDataHotSpot

It is possible to group these things in two groups:

• objects that represent data which is actually shown on the map:
  • Features
• objects that are abstract
  • everything else :)

I'm not sure to which of the groups the geometry classes belongs.

A compromise could be to use the classes of the first group with a pointer and all others as a value. In KML all items are children of GeoDataObject (except GeoDataCoordinates). See here.