VRT Simple Source fails when a source is an explicit overview band

[Lucian Plesea]

When a VRT simple source band is explicitly created from a specific overview band and the content is read, the following occurs:

• VRTDataset::CheckCompatibleForDatasetIO() returns TRUE
• VRTSimpleSource::DatasetRasterIO() is called

But an overview band does not necessarily have a valid poDS field, in which case DatasetRasterIO returns failure with no error message.

Even if the overview has a valid pointer to the parent dataset, the RasterIO performed by the parent dataset does not necessarily use the overview band as the one used to create the VRT, contrary to the purpose of creating an VRT from a specific overview.

Proposed Fix: In addition to the current code: Return FALSE from CheckCompatibleForDatasetIO()

• if any of the source bands don't have a valid parent dataset pointer
• if any of the source bands are overviews

Both of these conditions are not compatible with DatasetIO.

[Even Rouault]

Could you attach a patch for this ?

[Lucian Plesea]

Attaching patch against 1.11.2/frtms/vrt/vrtdataset.cpp

[Lucian Plesea]

The check for overview is wrong in the patch, give me a bit of time!

[Lucian Plesea]

Even better test

[Even Rouault]

trunk r29173, branches/1.11 r29174 "VRT: add more checks to CheckCompatibleForDatasetIO() to avoid issues with overview bands (patch by lplesea, #5954)"

[Even Rouault]

trunk r29192, branches/1.11 r29193 "VRT: additional fix for #5954 to avoid new warnings by CheckCompatibleForDatasetIO()"