28.01.2016, 00:05, Even Rouault kirjoitti:

Thanks for the pointer to the geometry codes in SF Common Architecture, somehow I overlooked it.

my point with adding the new capabilities was that drivers that wouldn't advertize the M capabilities would never see a M or ZM geometry / geometry type passed. See what the (non-virtual) methods OGRLayer::SetFeature(),CreateFeature() and GDALDataset::CreateLayer() do for curve geometries. Similar things could be done for M.

Hm. For example shape driver raises an error if the geometry type is not supported. I don't know what scenario would lead to that.

Assume that the user has data in GDAL with measures. She decides to save that using a driver, which does not support measures. The impact is that the measures are stripped out, which is ok if the data is discarded immediately after that but not if she wants to still do something with the measures. I'm not sure if documenting the side-effect is enough. However, the convert to non linear geometries is already there and this would follow that pattern. I guess this is a part of the bigger discussion whether we consider GDAL as a data storage for interactive tools for example or as a data processing library.

Ari

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