Before the NVTT upgrade, no DXT1a file would have been properly decoded:
they would all have been mistaken for a 8bpp greyscale due to a logic
issue in our code, which would have triggered a crash. I did not notice
the logic issue when performing the upgrade. As a result, decoding those
files now fails silently: their alpha bit will be ignored and they will
be handled as DXT1.
This patch fixes the logic and allows us to decode DXT1a properly, in
accordance with the format specifications. Currently, we do not use this
format.
Reviewed By: wraitii
Differential Revision: https://code.wildfiregames.com/D2522
This was SVN commit r23973.