I haven't properly tabulated this, but I guess at some point I (or someone motivated) has to inspect the iframe a of the webstores (itch io, gamejolt, Newgrounds, ...) and make a relation of what types of Feature-Policy are allowed in those. This would give a general idea of what is allowed and what isn't.
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My general feeling towards file download is that it's best to have it inside a Share action instead, which can have files attached to it. This is more portable - in Android these translate to intent. This avoids having to concede file permissions to an app and instead allows to work with these as they are needed - general file access in Android would require blank permission access to files, which is weird for a game.
Unfortunately SDL doesn't include anything similar to a share action so we would have to either maintain our on or contribute some version of this for SDL. I think in this specific case MAYBE maintaining our own is easier, but I would need to think about this.
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My general feeling towards file download is that it's best to have it inside a Share action instead, which can have files attached to it. This is more portable - in Android these translate to intent. This avoids having to concede file permissions to an app and instead allows to work with these as they are needed - general file access in Android would require blank permission access to files, which is weird for a game.
Unfortunately SDL doesn't include anything similar to a share action so we would have to either maintain our on or contribute some version of this for SDL. I think in this specific case MAYBE maintaining our own is easier, but I would need to think about this.