[mapguide-internals] Some pointers please for Integration into server code for MapGuide RFC 60

Bruce Dechant bruce.dechant at autodesk.com
Mon Mar 2 14:29:33 EST 2009


Please see my comments below.

Note: I will comment on the RFC60 in the other thread.


-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of UV
Sent: Thursday, February 26, 2009 9:35 PM
To: MapGuide Internals Mail List
Subject: [mapguide-internals] Some pointers please for Integration into server code for MapGuide RFC 60

Hi all,

I am working on  improvement of color palette quantization for PNG8 tiles.

The RFC has been set up in the wiki: MapGuideRfc60
Any further ideas and comments are greatly appreciated.

The general algorithm has been implemented within AGGImageIO.cpp and
I found some pieces of png C code in there and simply added another 2
methods (~100 lines) to it.

Whats remaining now is the clean integration into the server and the
configuration issues.
Being fairly new to the mapguide server I can use some help where to
find things.
Searching the whole codebase has turned out to be very unefficient.

Therefore I would appreciate some pointers into the code tree:
- where to add the color extraction code from the  map definitions
[Bruce Dechant] You could add it to the GetTile() method as it extracts the Map definition information and caches it for future use. 

- where is the best place to add the color palette in the resource tree.
[Bruce Dechant] I think as a new ColorPalatte resource that is referenced by the Map Definition. 
- where I can find example code that parses the map definition (for the
color extraction)

[Bruce Dechant] Here is some sample code that parses the map definition resource:

    // get the map definition from the resource repository
    Ptr<MgByteReader> content = m_resourceService->GetResourceContent(mapDefinition);
    Ptr<MgByteSink> sink = new MgByteSink(content);
    Ptr<MgByte> bytes = sink->ToBuffer();

    // parse the map definition
    MdfParser::SAX2Parser parser;
    parser.ParseString((const char*)bytes->Bytes(), bytes->GetLength());

    if (!parser.GetSucceeded())
        STRING errorMsg = parser.GetErrorMessage();
        MgStringCollection arguments;
        throw new MgInvalidMapDefinitionException(L"MgMap.Create", __LINE__, __WFILE__, &arguments, L"", NULL);

    // build the runtime map object from the parsed definition
    std::auto_ptr<MdfModel::MapDefinition> mdef(parser.DetachMapDefinition());

- whats the recommended way to throw an exception from the included C-code
 throw new std::exception("AGGImageIO.cpp:1086: the base color cannot be
found in the provided colormap: ABORT")
[Bruce Dechant] Aborting the program due to this failure is not a good idea - I assume that is just part of your sample exception comment and not what you really want to do. The existing AGG code has a couple of example exceptions - see _DWFCORE_THROW. These are DWF specific so I would suggest you introduce a new type something like _AGG_THROW.

thanks for your support.
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