[feat] Read dark/light theme on MacOS and Linux

[kkoomen]

Describe the problem

Currently, the API can only read out the current system theme on Windows, but not on MacOS.

The following code below will result in light even though I'm in dark mode.

import { appWindow } from '@tauri-apps/api/window';

appWindow.theme().then((theme) => {
  console.log(theme); // returns 'light' even though I'm in dark mode
});

Describe the solution you'd like

This should work on MacOS as well.

Alternatives considered

None.

Additional context

N/A

[keiya01]

https://indiestack.com/2018/10/dark-mode-series-introduction/
I think this is useful but I could not find some property in objc.

[keiya01]

This issue is resolved on macOS, but Linux has still this issue.

[Layendan]

Currently using Tao 0.11.2, Tauri 1.0.0, and MacOS 12.4.

Tested with your example using async/await instead of .then() and it did not work. It returned "light" no matter what system appearance I used. Using the provided "tauri://theme-changed" event listener DID return the correct appearance setting though.

Tested on two different MacBooks (M1 and x86) both resulted in the same problem.

[lucasfernog]

@Layendan support on Tauri will be available in the next release (either tomorrow or wednesday).