View source for Marble/TileDownload

=== Design considerations, ideas, thoughts, nothing final ===

Perhaps create an (abstract) interface / abstract class TileProvider? Not sure, if there is an use case.

Perhaps separation between http download and tile providing since http download is needed for wikipedia (and perhaps other stuff) integration also.

What about redirects? in general it seems to be a good idea to support them, but do we also need the ability to
forbid redirects of inform the user?

The TileLoader should be able to handle not only files, but also QByteArrays or whatever is delivered by the network plugin interface.


=== Documentation of existing code ===

Here are drop notes of understanding how downloading http stuff happens:

{{class|HttpDownloadManager|kdeedu|4.x}} is the entry point if you want to download http things.

This class handles download jobs by first creating a simple {{class|HttpJob|kdeedu|4.x}}, and providing it to one of the {{class|DownloadQueueSet|kdeedu|4.x}} classes which can behave according to various {{class|DownloadPolicyKey|kdeedu|4.x}}. 

A {{class|StoragePolicy|kdeedu|4.x}} belongs to the HttpDownloadManager to handle downloaded files properly.

It also relies on the {{class|PluginManager|kdeedu|4.x}} to provide a {{class|NetworkPlugin|kdeedu|4.x}} which implements the createJob

In the current imlementation (trunk just after 4.4 branching), there are many
HttpDownloadManagers, which in turn have their own PluginManager, StoragePolicy and DownloadQueueSets. This looks suboptimal and hard to evolve.

=== Current Work ===
- Work is ongoing to have only one PluginManager belonging in the {{class|MarbleModel|kdeedu|4.x}}, which others could use when needed, currently
 * {{class|LayerManager|kdeedu|4.x}},
 * {{class|HttpDownloadManager|kdeedu|4.x}},
 * {{class|PositionTracking|kdeedu|4.x}}
So HttpDownloadManagers would need to use it.

- Many HttpDownloadManagers created "in the wild" for different purposes, like in 
 * {{class|AbstractDataPluginModel|kdeedu|4.x}} (and so all *PluginModel which inherit...),
 * {{class|MarbleModel|kdeedu|4.x}},
 * {{class|TwitterPlugin|kdeedu|4.x}}
Maybe one would be enough, given the DownloadQueues and StoragePolicies framework...

=== Design proposal ===

to be done