Entities
The whole document is one plain struct, vv_core::Project (model.rs). There is no node graph: every clip carries a fixed EffectStack. The project is owned by a vv_session::Session together with its undo History; every change goes through a command (see Commands, Undo/Redo).
Entity diagram
Clip sources
| ClipSource | Content |
|---|
Media(MediaId) | A file of the media pool, or a compound clip (a pool item pointing at a timeline). |
SolidColor | Colour from EffectStack::color. |
Text | Title from EffectStack::title. |
Adjustment | No content: its effects apply to the composite of the tracks below. |
Time on a clip
| Field | Meaning |
|---|
timeline_start, timeline_len | Position on the timeline, in timeline frames. |
source_offset | Start in the media, also in timeline frames: a conformed clip can start mid source frame. |
rate, speed | Private. rate = timeline frames per source frame (fps conform ÷ speed); written only through conform / set_speed so the two never drift. |
source_frame_at() | The single timeline → source mapping, shared by preview and export. |
Invariants
| Rule | Why |
|---|
Track::clips is sorted by timeline_start and never overlaps. | At most one clip per track covers a frame; lookups and compositing rely on it. |
| Track order is compositing order, bottom → top. | V1/A1 labels are derived per kind (track_label), never stored. |
| Each timeline has its own fps and resolution. | Clips from other rates are conformed through Clip::rate. |
A CrossTransition stores only the two clip ids. | Its window is recomputed from the clips' current edges; commands that split, delete or move a clip to another track must call take_crossings_for. |
| A linked group has no entity. | Membership is Clip::linked_group; selection, drag and delete treat the group as a unit. |
Compound clips
A timeline is used inside another through a pool MediaItem whose compound is Some(TimelineId). Its meta is recomputed from the nested timeline (sync_compound_meta) and its content_hash is bumped on every change, which invalidates cached composited frames without comparing timelines. would_create_a_cycle forbids nesting a timeline inside itself; MAX_COMPOUND_DEPTH (16) is only a safety net.
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