Respect XDG_CONFIG_HOME on macOS when resolving config.toml

[Wolfsrudel]

Problem

On macOS, abtop does not respect XDG_CONFIG_HOME when resolving its configuration file.

The documentation says the configuration is stored at:

~/.config/abtop/config.toml

However, abtop currently resolves the path with:

dirs::config_dir().map(|dir| dir.join("abtop").join("config.toml"))

On macOS, dirs::config_dir() returns:

~/Library/Application Support

Consequently, abtop reads and writes:

~/Library/Application Support/abtop/config.toml

This happens even when the user has explicitly configured:

export XDG_CONFIG_HOME="$HOME/.config"

As a result, $XDG_CONFIG_HOME/abtop/config.toml is silently ignored. This is confusing because the documented configuration file exists, but settings such as theme = "btop" have no effect.

Requested behavior

When XDG_CONFIG_HOME is set and non-empty, abtop should read and write:

$XDG_CONFIG_HOME/abtop/config.toml

For example:

export XDG_CONFIG_HOME="$HOME/.config"

should make abtop use:

~/.config/abtop/config.toml

When XDG_CONFIG_HOME is unset or empty, abtop can retain its current platform-specific fallback:

~/Library/Application Support/abtop/config.toml

Suggested resolution order

1. $XDG_CONFIG_HOME/abtop/config.toml when XDG_CONFIG_HOME is set and non-empty.
2. dirs::config_dir()/abtop/config.toml as the platform-specific fallback.

For example:

fn config_path() -> Option<PathBuf> {
    std::env::var_os("XDG_CONFIG_HOME")
        .filter(|value| !value.is_empty())
        .map(PathBuf::from)
        .or_else(dirs::config_dir)
        .map(|dir| dir.join("abtop").join("config.toml"))
}

The same resolved path should be used for both loading and saving configuration.

Steps to reproduce

1. On macOS, set:

   export XDG_CONFIG_HOME="$HOME/.config"

2. Create ~/.config/abtop/config.toml with:

   theme = "btop"

3. Create or retain ~/Library/Application Support/abtop/config.toml with:

   theme = "catppuccin"

4. Start abtop.

Actual behavior

abtop uses the configuration under ~/Library/Application Support/abtop/ and displays the Catppuccin theme.

The file under $XDG_CONFIG_HOME/abtop/ is ignored.

Expected behavior

Because XDG_CONFIG_HOME is explicitly set, abtop should use $XDG_CONFIG_HOME/abtop/config.toml and display the btop theme.

Environment

• abtop: 0.5.5
• Operating system: macOS
• Installation method: release shell installer
• Relevant dependency: dirs 6.0.0

Documentation

The configuration documentation should also describe the lookup order and mention the macOS fallback path.