filmcraft/crates/ui-egui/README.md

FilmCraft interface

The egui frontend draws panels and dialogs, and dispatches project changes through the engine. Interactive controls keep stable automation ids regardless of the interface language.

Transition drop previews

Dragging a video or audio transition over a compatible clip shows its actual time span, the selected cut and an In/Out label. Shared cuts center the span; isolated edges use a one-sided span. The preview uses the engine's read-only transition planner, including Timeline duration preferences, and release dispatches effects.apply with the same edge. Locked tracks and incompatible clip types show no valid transition preview. Ordinary effects retain their clip outline. timeline.transitionDropPreview exposes the span and edge to automation.

transition_drop_ui covers both edges of short video/audio clips, hover without project edits, the committed span and undo. Set FILMCRAFT_UI_SNAPSHOT_DIR to render screenshots with wgpu.

Localisation

Edit > Language offers English, Japanese, Spanish, Brazilian Portuguese, Ukrainian, Simplified Chinese, German, Russian, French and Indonesian (which covers the whole interface). The language is stored in the engine's general.interfaceLanguage preference, restored on startup, and also available in Settings > General. Its default, System Language (system), follows the operating system: the first of the user's preferred languages that the interface has (the host supplies them through HostHooks::system_languages: sys-locale on the desktop, navigator.languages on the web), otherwise English. The app.language.* UI commands and prefs.set reach it through the control channel. Japanese requires a craft-fonts build or a suitable installed font.

English source strings are lookup keys in src/i18n/<code>.tsv. tl! translates literals, tlf! fills translated templates, and i18n::t translates names from registries. Placeholder values (including user filenames containing braces) are inserted literally. Catalog translations are original work using ordinary language, without proprietary localisation resources.

Spanish, Japanese, Simplified Chinese and French cover menus, panels, dialogs, settings and registry labels. Searches accept both the translated label and its English source, including Unicode capitals. Project content, command ids and preference values retain their original values. Engine errors, CLI and MCP messages remain English. Brazilian Portuguese and Ukrainian currently cover the core menus, German every menu; they fall back to English elsewhere.

Verification: cargo test -p filmcraft-ui-egui checks catalog syntax, duplicate keys, placeholders, literal/menu/registry coverage and UI behaviour; cargo xtask ci runs the workspace gates. Visual checks use the control channel to switch language and capture the resulting panels.

Source playback

source_playback.rs auditions media independently of Program playback. It reuses MediaSource decoding, output mapping, the device clock and the desktop play-ahead buffer. Only one monitor owns the device at a time. Source frame jobs use the existing frame server and Source resolution. The live project, undo stack and timeline playhead are unchanged. See monitor documentation for behavior, commands, limitations and regression tests. Source playback tests use synthetic demo media and fake audio outputs; no third-party assets are introduced.

Source drag controls snapshot the selected span and dispatch timeline.place for video, audio, or linked video/audio. Full-clip marks are implicit until set by the user. The engine owns edits, range validation and undo; the UI owns the drag gesture. See source_drag_ui and the engine's source_placement_tests for regression coverage.

Source range handles use transient gesture previews and the engine's integer-frame source_monitor::adjust_range; release dispatches one mark edit. Monitor command routing keeps Source navigation, markers and marked-range playback separate from Program.

Pane layout controls

Dock transactions and pointer targets use craft-ui::docking; bounded split geometry and keyboard-accessible resize handles use craft-ui::layout. FilmCraft adapts its existing saved dock tree and panel identities to the shared model. Panel tabs or their header grip can move between tab groups, split at an edge, reorder, or float when released with Cmd/Ctrl. Floating panels move by their empty header and resize from the bottom-right corner. Timeline sequence tabs retain their sequence-opening, closing and horizontal reorder behavior; the header grip moves the Timeline panel. Workspace saves retain floating groups alongside the legacy layout JSON, and workspaces without floating data still load. Automation IDs and workspace commands remain the integration boundary.

Tools and dock tabs expose their actual egui widget IDs, paint keyboard focus, and support Tab/Shift-Tab traversal and Space/Enter activation. Control-injected keys can reach focused widgets in a background window. The optional --control-input-only native launch mode isolates automation from native widget/menu input; ui.inspect reports native and effective focus separately. Focus and input-ownership regressions cover document/playhead preservation.

Compact monitor layouts separate the current and duration timecodes from zoom, resolution and settings. Source video/audio drag choices retain their existing placement behavior. Transport buttons use craft-ui::layout::fit_toolbar; commands beyond the available width remain available through More, including their selected state and Source/Program routing. A scrolling fallback retains all commands if even More cannot fit. monitor_geometry checks the painted readouts, control bounds, overflow actions and Source drag payloads across monitor widths and themes.