[flutter/plugins] Support shared_preferences

[stuartmorgan-g]

This is simple for macOS since it can use NSUserDefaults as on iOS. Investigation is needed to figure out what the best equivalents would be for Linux and Windows.

[axellebot]

So you forked the shared_preferences package from flutter/plugins repository into a subfolder and they will be merged later, right ?

[stuartmorgan-g]

There's no forking involved, the "plugins" in the flutter_plugins directory here contain only the desktop platform implementations. The are meant to be combined with the actual plugins.

[stellarbear]

This is a must have desktop feature

[axellebot]

For Windows though, since the current plugin API is expected to completely change (right now it shares the Linux C++ API; I expect it to switch to C# later), that's probably premature; discussions about how to proceed with that are still in progress. In the short term, I think adding a Windows implementation of shared_preferences here, with the expectation that it would move to flutter/plugins later, would be reasonable.

@stuartmorgan ATM if we want the plugin to work on windows we need to add linux support with GTK since windows and linux plugins are sharing Linux C++ lib, right ? Or I totally miss understood ?

[stuartmorgan-g]

Sorry, I'm not following the question. Windows and Linux implementations are entirely unrelated, so no, a Linux implementation is not required for a Windows implementation to exist. Even on Linux I don't see where GTK would come into it since shared_preferences has no UI.

I recommend looking at the Windows example plugin to see the basics of implementing a Windows plugin with the C++ API.

[axellebot]

I probably miss understood the purpose of GTK, I thought GTK was used as a platform SDK as we do with Android SDK and iOS SDK.

Glad to hear that you created #408 for windows example, I will take a look ! Thanks 👌

[lucacasonato]

Do Windows and Linux have equivalents to NSUserDefaults? I presume we will have to write a json or xml file to disk (sorta like android shared preferences works under the hood). For Linux this can be in $XDG_CONFIG_HOME/bundle_id/shared_prefrences.json (https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html). For Windows we can probably use %AppData%bundle_id/shared_prefrences.json.

I haven't really done C++ stuff extensively so it is probably best that someone who knows more about this implements this.

[stuartmorgan-g]

@csells has been looking into a Windows implementation. I believe what you're describing is basically the approach he is taking.

[csells]

Correct.