cedinia – Architecture Guide

Overview

Android (and secondary desktop) GUI. Architecture mirrors krokiet but adapted for mobile constraints: touch-optimized layout, JNI file picker, runtime permissions, system insets, and no video tools (FFmpeg unavailable on Android).

Entry Points

Android (src/lib.rs):

#[unsafe(no_mangle)]
fn android_main(android_app: AndroidApp) {
    android_logger::init_once(…);        // Log to logcat
    setup_android_paths(&android_app);   // JNI: get /data and /cache paths
    file_picker_android::init(&android_app); // Load DEX + init JNI
    slint::android::init(android_app.clone()).expect(…);
    app::run_app_with_insets(inset_bottom_px, scale, android_app);
}

Desktop (src/app.rs):

pub fn run_app() {
    setup_logger_cache();
    run_app_with_insets(0.0, 1.0, ());
}

Both converge at run_app_inner(): load settings → create MainWindow → wire callbacks → start worker thread → run event loop.

Source Layout

cedinia/src/
├── lib.rs                         # Android entry (#[no_mangle] android_main)
├── app.rs                         # Desktop entry + shared run_app_inner()
├── bin/cedinia.rs                 # Desktop binary wrapper
├── common.rs                      # Column index enums (StrData*, IntData*)
├── model.rs                       # FileEntry toggle/count logic
├── scan_runner.rs                 # Worker thread + ScanRequest/ScanResult
├── scanners.rs                    # Tool-specific scan builders
├── notifications.rs               # Desktop notifications
├── set_initial_gui_infos.rs       # Initial GUI state
├── thumbnail_loader.rs            # Async image thumbnail loading
├── translations.rs                # translate_items() – populates Translations global
├── volumes.rs                     # Storage volume detection
├── localizer_cedinia.rs           # flc! macro, LANGUAGE_LIST, apply_language_preference()
├── file_picker_android.rs         # JNI + embedded DEX file picker
├── callbacks/
│   ├── callbacks.rs               # Module re-exports
│   ├── scan.rs                    # wire_scan() – scan/stop/tool-change callbacks
│   ├── selection.rs               # wire_selection() – delete + model access
│   ├── directories.rs             # wire_directories() – add/remove include/exclude dirs
│   └── misc.rs                    # wire_permission(), language, open-path, settings
├── settings/
│   ├── mod.rs                     # CediniaSettings struct; load/save JSON
│   └── gui_settings_values.rs     # StringComboBoxItems – combo box option arrays
└── ui/
    ├── main_window.slint          # Root component
    ├── app_state.slint            # Global AppState, GeneralSettings, tool-specific globals
    ├── common.slint               # Enums: ActiveTool, ScanState, ConfirmPopupAction
    ├── colors.slint               # CediniaColors theme
    ├── settings_screen.slint      # Settings screen layout
    ├── settings_components.slint  # ToggleRow, SegmentRow, DropdownRow, TextInputRow
    ├── similar_images_gallery.slint
    ├── directories_screen.slint   # Add/remove directory paths
    ├── components.slint           # Shared components
    └── …

Slint Performance: ListView vs. for-in / ScrollView

When displaying more than a few dozen items, always use ListView (from std-widgets.slint) rather than a bare ScrollView / for loop inside a VerticalLayout.

// SLOW – instantiates every item upfront, O(n) per frame
ScrollView {
    VerticalLayout {
        for item in model : Row { ... }
    }
}

// SLOW - same as above
VerticalLayout {
    for item in model : Row { ... }
}

// FAST – virtual scroll via Flickable's Repeater optimization
ListView {
    for item in model : Row { ... }
}

ListView uses Slint's Repeater-inside-Flickable optimization: only visible rows (plus a small buffer) are instantiated at any given time. With a plain ScrollView + VerticalLayout, all N items are created and visited on every frame.

Reference: Slint issue #11021.

Scan Data Flow

1. User selects tool + taps Scan → AppState.on_scan_requested()
2. scan.rs: collect settings from globals → build ScanRequest
3. ScanRequest sent to worker thread via channel
4. Worker: configure tool struct → tool.search(stop_flag, progress_sender)
5. Results stored; ScanResult sent back to main thread
6. invoke_from_event_loop: populate model, update AppState.scan_state

Slint UI Architecture

Settings are stored in Slint globals (not set from Rust at startup):

• GeneralSettings – language, file sizes, cache, extension filters
• DuplicateSettings, SimilarImagesSettings, SameMusicSettings, …
• AppState – scan state, active tool, result models, all callbacks

apply_settings_to_gui() (settings/mod.rs) reads CediniaSettings from JSON and populates these globals. collect_settings_from_gui() reads them back for saving.

DropdownRow (ui/settings_components.slint)

Custom settings row with a scrollable popup:

• Tapping the row opens a PopupWindow.
• Height capped at min(options.length * 48px, 384px).
• Content wrapped in ScrollView with viewport-height = options.length * 48px, allowing the 27-language list to scroll.

Translation System

Same workaround as krokiet:

• All UI text bound to Translations global properties.
• translate_items() in src/translations.rs populates them via flc!("key").
• LANGUAGE_LIST in localizer_cedinia.rs defines the 27 supported languages.
• GeneralSettings.language_options in ui/app_state.slint is hardcoded and must match LANGUAGE_LIST exactly.
• Language index stored in GeneralSettings.language_idx; code stored in CediniaSettings.language.

Settings (src/settings/mod.rs)

JSON file:

• Desktop: ~/.config/Czkawka/cedinia_settings.json
• Android: app-private storage (/data/data/…/files/config/)

CediniaSettings (serde Serialize/Deserialize) covers all tool parameters. Default implementation delegates to serde_json::from_str("{}") so all #[serde(default)] values are used.

Android-Specific Code

File Picker (src/file_picker_android.rs)

A Kotlin helper class is compiled at build time (via android-build crate) and embedded as DEX bytecode:

include_bytes!(concat!(env!("OUT_DIR"), "/classes.dex"))

At runtime:

1. DEX is loaded into an InMemoryDexClassLoader.
2. CediniaFilePicker instance created via JNI.
3. launch_pick_directory(is_include) calls the Java ACTION_OPEN_DOCUMENT_TREE intent.
4. Result arrives via Java_CediniaFilePicker_onDirectoryPicked() JNI callback → dispatched to Rust via invoke_from_event_loop().

Storage Permissions

Runtime permission check/request via JNI. AppState.storage_permission_granted gates scan initiation.

System Insets

Android edge-to-edge layout requires padding for navigation bars. Inset sizes are passed from Kotlin via android_app.content_rect() and plumbed through to Slint as layout properties.

Android Paths via JNI

setup_android_paths() calls getFilesDir() and getCacheDir() on the Activity to find private storage paths; these are set as environment variables and used by czkawka_core's config path logic.

Differences from krokiet

Key Dependencies

Always

Android only

Desktop only

Build

[build-dependencies]
slint-build = "1.15"
android-build = "0.1.2"   # Compiles CediniaFilePicker.java → classes.dex

Android Manifest Permissions

READ_EXTERNAL_STORAGE, WRITE_EXTERNAL_STORAGE, MANAGE_EXTERNAL_STORAGE, POST_NOTIFICATIONS

Optional Features (forwarded to czkawka_core)

heif, libraw, libavif, xdg_portal_trash