Implement XDG Desktop Portal Settings D-Bus service in Rust

[Copilot]

Implements a minimal D-Bus service for org.freedesktop.impl.portal.Settings with all documented settings from the XDG portal specification.

Architecture

Workspace structure:

• portal_setting - Library implementing the D-Bus interface with type-safe settings storage
• portal_setting_cli - Service executable that registers and serves the D-Bus interface
• portal_setting_client - Integration test client that exercises all settings

Implementation

Settings coverage:

• org.freedesktop.appearance: color-scheme (u32), accent-color (f64 tuple), contrast (u32)
• org.gnome.desktop.interface: gtk-theme, icon-theme, cursor-theme, font-name, monospace-font-name, clock-format (all strings)
• org.gnome.desktop.privacy: remember-recent-files (bool), recent-files-max-age (i32)

Key features:

• Type validation on setting updates with signature checking
• Namespace-based filtering in ReadAll operations
• Thread-safe async storage using Arc<RwLock<HashMap>>
• zbus 4.0 interface macros for D-Bus integration

CI workflow:

• Builds workspace and runs unit tests
• Integration test runs service + client in dbus-run-session
• On tag push: publishes release binary as GitHub artifact

Usage

# Start the service
cargo run --bin portal-setting-service

# In another terminal, test all settings
cargo run --bin portal-setting-client

The service registers at org.freedesktop.impl.portal.Settings and serves the interface at /org/freedesktop/portal/desktop per XDG portal conventions.

Original prompt

Implement a Rust workspace containing:

• portal_setting: a library crate that implements the D-Bus interface org.freedesktop.impl.portal.Setting and supports all known settings as documented at https://flatpak.github.io/xdg-desktop-portal/docs/doc-org.freedesktop.portal.Settings.html. It provides type-checking on setting update, and filtering on key listing.
• portal_setting_cli: an executable crate that runs the D-Bus service using the library.
• portal_setting_client: a test executable that exercises all settings for read/write, confirming values.
• A thorough README with usage instructions and documentation.
• A CI workflow (.github/workflows/ci.yml) that builds, runs tests, and publishes a release artifact.
• CI workflow should build the workspace, run the client test against the server, and on tag push, publish the built executable as a release.

Refer to detailed design and sample files in conversation. All files below must be created:
*Cargo.toml (workspace)
*portal_setting/Cargo.toml, src/lib.rs
*portal_setting_cli/Cargo.toml, src/main.rs
*portal_setting_client/Cargo.toml, src/main.rs
*README.md
*.github/workflows/ci.yml

The CI workflow should:

• Build all workspace members
• Run tests (ensure service and client interaction)
• On new tag push, build release binary for cli and publish as GitHub release artifact.

This pull request was created as a result of the following prompt from Copilot chat.

Implement a Rust workspace containing:

• portal_setting: a library crate that implements the D-Bus interface org.freedesktop.impl.portal.Setting and supports all known settings as documented at https://flatpak.github.io/xdg-desktop-portal/docs/doc-org.freedesktop.portal.Settings.html. It provides type-checking on setting update, and filtering on key listing.
• portal_setting_cli: an executable crate that runs the D-Bus service using the library.
• portal_setting_client: a test executable that exercises all settings for read/write, confirming values.
• A thorough README with usage instructions and documentation.
• A CI workflow (.github/workflows/ci.yml) that builds, runs tests, and publishes a release artifact.
• CI workflow should build the workspace, run the client test against the server, and on tag push, publish the built executable as a release.

Refer to detailed design and sample files in conversation. All files below must be created:
*Cargo.toml (workspace)
*portal_setting/Cargo.toml, src/lib.rs
*portal_setting_cli/Cargo.toml, src/main.rs
*portal_setting_client/Cargo.toml, src/main.rs
*README.md
*.github/workflows/ci.yml

The CI workflow should:

• Build all workspace members
• Run tests (ensure service and client interaction)
• On new tag push, build release binary for cli and publish as GitHub release artifact.

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[jwinarske]

@copilot The implementation is missing interface version, exposed