19.02.2016, 02:23, Even Rouault kirjoitti:
Le vendredi 19 février 2016 00:55:21, Nyall Dawson a écrit :
Hi all,
I'm aware that for drivers I can use OGR_Dr_TestCapability to
determine whether a particular driver as a specific capability. But is
there anyway to test whether a specific driver also has support for a
layer capability?
The situation is that I'd like to populate a list with all available
OGR drivers for which a created layer would then be able to support
SequentialWrite, DeleteFeature, RandomWrite and CreateField.
What would be the best way to go about this?
There seems to be growing interests for such topic (see yesterday similar
thread : https://lists.osgeo.org/pipermail/gdal-dev/2016-February/043782.html
)
The way to go is to add such capability flags at the driver metadata level.
This is now possible since GDAL 2.0 since OGR drivers can expose arbitrary
metadata items.
What has to be done :
- define which capabilities must be exposed
- enhance drivers to advertize them
In this case the question is about existing layer capabilities. One
obstacle to testing them is that there is usually no way to create
"blank" or minimal layer objects. For example Shapefile layer
constructor requires all kinds of information and it represents an
actual file (which can be in memory, though).
Blank or minimal layer objects could be useful as they can answer
capability questions - the TestCapability method usually requires no or
only minimal property information (is the layer read only or not, is
filtering on).
Hm. Since the property information plays a part, the capability is not
always a simple on/off issue, but the answer to a question whether a
layer has a specific capability can also be "it depends" if you only
know the driver.
Ari
Nyall
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