Why I think it is needed:
You can open a file with FILE_ATTRIBUTE_TEMPORARY as an attribute to CreateFileW function, and the file should stay in cache only. But Windows can flush it on disk in any moment, it if want's to. For example, on my system I were only able to create 1-2 MB file. Just 10 MB—and file is written to disk. And I have about 8 GB of free memory. I feel that it's possible that Windows just ignore this flag and always write file, if some conditions are met. For example, if there is less memory available.
It would be great though to at least have the ability to make small and unreliable in-memory files. It's better than nothing.
Unfortunately, Rainmeter can't open images created this way because it doesn't specify FILE_SHARE_WRITE when opening files. But I can't close the file handle because as soon as I do it, the file is flushed to disk.
Can you please accept my pull request that fixes this?