Timeline and keyframes

The timeline runs along the bottom of the editor. It has a transport (play/pause and record), a loop duration field, a ruler, and one row per animated view with a keypoint for each of its keyframes.

The controls

Control	What it does
/	Plays or pauses the loop. Space does the same thing.
	Arms keyframe recording. Red means armed.
Loop duration	How many seconds one loop lasts.
Playhead	Drag to scrub. The app under test holds the frame the playhead points at.

Space works anywhere in the editor except while you are typing in a text field, so you can play back without moving the mouse out of the viewport.

Recording a keyframe

1. Select the view in the simulator viewport.
2. Position the playhead at the time you want the pose to land.
3. Arm recording with the record button.
4. Drag the view in the viewport. When you release, a keyframe is written at the playhead with the position you dropped it at.

Repeat for each pose. The order you record in does not matter — a keyframe goes where the playhead is, not after whatever you recorded last.

Recording on top of an existing keypoint replaces it rather than stacking a second keyframe at the same time. Two keypoints closer together than a millisecond or so are treated as the same keypoint, because a zero-length keyframe cannot be interpolated.

Nothing records without recording armed

With recording off, dragging a selected view moves it in the viewport but writes nothing. That is deliberate — it lets you reposition and inspect without editing — but it is the most common reason a drag seems not to have taken.

Scrubbing

Dragging the playhead while playback is stopped holds every animated view at the values its track reaches at that time, so the simulator shows the frame the timeline is pointing at. It is the fastest way to check a pose.

Scrubbing is disabled while the animation is playing. During playback the playhead is reporting the runtime's own clock position back to you, and dragging it would fight that clock.

Loop duration

The loop length is a property of the timeline, not of any one animation. Every track is padded out to the loop: a view that stops moving after half a second holds its final pose until the loop comes around again. That is what keeps tracks of different lengths restarting together.

• Default: 3 seconds
• Range: 0.1 to 60 seconds
• Remembered across launches, since it reflects how you work rather than any one project

Changing it is pushed to the running app immediately, so playback in the simulator always covers the span the timeline draws.

Deleting a keyframe

Right-click a keypoint on its row and choose Delete Keyframe.

The remaining keyframes stay at the times they were recorded at. This is worth stating because the file stores durations relative to the preceding keyframe — removing one naively would drag everything after it earlier by the gap that disappeared. The editor refolds the durations so nothing else moves.

What gets written

Keyframes are held in memory as you record and written to the project's animations/animation.inertia on save — autosave every 10 seconds, or when you close the project. Reopening a project loads its tracks back and parks each playhead at the end of what was recorded, so recording continues after the existing keyframes.

See Animation files for the format.