Symlink to symlink to file preload support

[lch361]

Hi. I stumbled upon this pretty nice software, but immediately encountered a problem: hyprpaper can preload only a path to file or path to a symlink that gets dereferenced once. Symlinks to symlinks do not work - well, not anymore :)

[lch361]

There is one problem though: recursive symlinks cause an exception and I have no idea how it's better to handle it in this program. Should it become a parse error, or a debug log, or exception is fine?

[vaxerski]

Should it become a parse error, or a debug log, or exception is fine?

probably debug log

[lch361]

..so I viewed code a little bit more - and turns out, every call to std::filesystem::exists can throw an exception if too many levels of symlinks. Handling these errors around the project would require a separate pull request, I think.

For now, I'll leave this pull request as is, sorry. I can't go right here through multiple parts of the project to handle every std::filesystem function, there has to be a better way.

[vaxerski]

can't we use canonical?

[vaxerski]

sure, we probably can just write a wrapper func in the future

[lch361]

can't we use canonical?

That works too, but also checks whether a file exists (throws an exception/returns an error if it doesn't). And g_pConfigManager->m_dRequestedPreloads contains only paths to existing files. Seems like unnecessary double checking: wallpaper target creation (line 138) should fail anyway if there are any problems with file.

[vaxerski]

yes but canonical is 1 line meanwhile your thing is like 10

[lch361]

Hm.. Then, it may be better to remove exist check in src/config/ConfigManager.cpp (line 70), replace it with std::filesystem::canonical, and leave src/Hyprpaper.cpp without any excessive checks. Or vice versa: have all checks only in src/Hyprpaper.cpp.

[vaxerski]

exist check won't crash, and it shouldn't. We can leave it intact.

[lch361]

It indeed shouldn't crash: instead of throwing an exception, canonical can return an error code through 2nd argument.
In src/Hyprpaper.cpp, we can do something like this:

        std::error_code ec;
        auto create_wp = std::filesystem::canonical(wp, ec);
        if (ec.value() != 0) {
            Debug::log(ERR, "Error preloading %s: %s", wp.c_str(), ec.message().c_str());
            break;
        }

But it takes near-same amount of lines

[vaxerski]

I still prefer not rewriting STL functions we already included

[lch361]

I still prefer not rewriting STL functions we already included

My last written solution is not rewriting any STL functions, as we can see. What's the problem?

[vaxerski]

canonical does the same in my eyes. It won't throw because of a non-existent file because we check for that.

[lch361]

But there is a (albeit very small) possibility that a file gets removed between config parsing and wallpaper target creation. I think best way is to check for file existance only once - that is, only when actually preloading the image. Filesystem is volatile, and changes independently of our program, so sequent checks mean nothing.