Revision as of 10:43, 30 January 2011

ModelView framework in Marble

Marble uses Qt's Model/View framework as a way to signal updates to a model to interested parts. In that respect, a Model class can wrap any possible data.

The Model-View framework is designed to hide the details of the model content, and to present it in a standardised way to views. The advantage of this solution is that the View need not know much about the data it presents.

The multiple models and proxies in Marble each fit the purpose of feeding some GeoData classes to interested widgets. Those models are fed by the Expression error: Unrecognized word "x"..

Here is the list of Model and Proxy classes, and a description of how they are used.

GeoDataTreeModel

The Expression error: Unrecognized word "x". represents the list of all Expression error: Unrecognized word "x". registered through the Expression error: Unrecognized word "x"..

It has signals/slots to react to files being added or removed in the FileManager.

It is used as the base model for GeoDataDocuments.

The Expression error: Unrecognized word "x". renders all Expression error: Unrecognized word "x". related placemarks.

FileViewModel

The Expression error: Unrecognized word "x". represents the list of opened files. The Expression error: Unrecognized word "x". appends the documents it opens. It is used by the Expression error: Unrecognized word "x"..

KDescendantsProxyModel

The Expression error: Unrecognized word "x". is used to flatten the tree of GeoData features. It represents the list of all Placemarks of all opened files.

The Expression error: Unrecognized word "x". uses that proxy model to provide the list of placemarks to search for, and the Expression error: Unrecognized word "x". uses it also to determine layouting on the map.

@@ Line 3: / Line 3: @@
 Marble uses Qt's Model/View framework as a way to signal updates to a model to interested parts. In that respect, a Model class can wrap any possible data.
-The multiple models in Marble each fit the purpose of feeding some GeoData classes to interested widgets. The way those models are fed could be improved however:
+The Model-View framework is designed to hide the details of the model content, and to present it in a standardised way to views. The advantage of this solution is that the View need not know much about the data it presents.
-== Model and Data Location ==
+The multiple models and proxies in Marble each fit the purpose of feeding some GeoData classes to interested widgets. Those models are fed by the {{class|FileManager|kdeedu|4.x}}.
-* At the moment, each Model contains the list/vector/tree of data it presents. This is not a problem per se, unless all those models present the same data, and retain their own copies. Once the time to edit this data comes, it is tedious or quite impossible to trace back all those copies.
+Here is the list of Model and Proxy classes, and a description of how they are used.
-The solution to this is twofold:
+=== GeoDataTreeModel ===
-** keep data unique in one store (wherever that is, a Model class or a list in one Manager)
+The {{class|GeoDataTreeModel|kdeedu|4.x}} represents the list of all {{class|GeoDataDocument|kdeedu|4.x}} registered through the {{class|FileManager|kdeedu|4.x}}.
-** Try and manipulate references to the data in the Models in such a case: with one change to the central data, multiple models can be notified and each react differently for the views they feed.
-== Model or not Model ==
+It has signals/slots to react to files being added or removed in the FileManager.
-* The Model-View framework is designed to hide the details of the model content, and to present it in a standardised way to views. The advantage of this solution is that the View need not know much about the data it presents.
+It is used as the base model for GeoDataDocuments.
-This solution however is not a one size fit all, because an interested class with some knowledge of the GeoDataTypes for example would be far better off manipulating the methods of GeoData classes.
+The {{class|GeometryLayer|kdeedu|4.x}} renders all {{class|GeoDataGeometry|kdeedu|4.x}} related placemarks.
-As a consequence, a choice should be made whether to access GeoData through the model-view framework (nice for a List Widget or for a generic presentation of 'data as a tree', really not so nice for a class which for example would like to calculate the bounding box of all geometric data of a GeoDataDocument, or even for the File read/write, as the knowledge of data types is really known).
+=== FileViewModel ===
+The {{class|FileViewModel|kdeedu|4.x}} represents the list of opened files. The {{class|FileManager|kdeedu|4.x}} appends the documents it opens.
+It is used by the {{class|FileViewFloatItem|kdeedu|4.x}}.
-== State of the Model ==
+=== KDescendantsProxyModel ===
+The {{class|KDescendantsProxyModel|kdeedu|4.x}} is used to flatten the tree of GeoData features. It represents the list of all Placemarks of all opened files.
-There are multiple models with various levels of implementation. Some are needed, others should die...
+The {{class|MarbleControlBox|kdeedu|4.X}} uses that proxy model to provide the list of placemarks to search for, and the {{class|PlacemarkLayout|kdeedu|4.x}} uses it also to determine layouting on the map.
-Here is the list of Model class, and a description of how they are used.
-=== QAbstractItemModel ===
-* {{class|GeoDataDebugModel|kdeedu|4.x}}
-It represents a data file, parsed into a {{class|GeoDataDocument|kdeedu|4.x}} tree structure.
-It is used by the {{class|DataViewPlugin|kdeedu|4.x}} debug plugin (and is broken atm)
-* {{class|GpxFileModel|kdeedu|4.x}}
-It represents a list of gpx data file represented as {{class|GpxFile|kdeedu|4.x}}
-This was originally intended to but used as the model for the File List View ( which is accessible by running marble with --enableFileView ) but has since been replaced by the FileViewModel.
-The model that is in the GpsLayer is currently only being used as a collection class and is deprecated. This, along with the whole current GPX implementation, needs to be removed and updated to the current concepts in Marble. See [[Projects/Marble/GPXStatus|Gpx Status]]
-* {{class|MarbleGeometryModel|kdeedu|4.x}}
-It represents the {{class|GeoDataGeometry|kdeedu}} and the {{class|GeoDataFeature|kdeedu|4.x}} items of the last opened {{class|GeoDataDocument|kdeedu|4.x}}.
-It is used by the {{class|GeoRenderPlugin|kdeedu|4.x}} to access the list of vector data to draw it.
-=== QAbstractListModel ===
-* {{class|FileViewModel|kdeedu|4.x}}
-It represents the list of opened files. The {{class|PlacemarkManager|kdeedu|4.x}} appends the documents it opens, and the {{class|MarbleWidget|kdeedu}} appends the gpx files it opens.
-It is used by the {{class|FileViewFloatItem|kdeedu|4.x}} and manipulated by the {{class|PlaceMarkManager|kdeedu|4.x}} and the {{class|MarbleModel|kdeedu|4.x}}.
-* {{class|MarbleGeoDataModel|kdeedu|4.x}}
-It represents a list of {{class|GeoDataDocuments|kdeedu|4.x}}. Only the {{class|PlacemarksPlugin|kdeedu|4.x}} uses it
-It is used by no other code.
-* {{class|MarblePlacemarkModel|kdeedu|4.x}}
-It represents the list of all Placemarks of all opened kml files. the {{class|PlaceMarkManager|kdeedu|4.x}} appends all the placemarks after reading a file.
-It is used by the {{class|MarbleControlBox|kdeedu|4.X}} to provide the list of placemarks to search for, and by the {{class|PlacemarkLayout|kdeedu|4.x}} to determine layouting on the map.