feat(scene)!: overlays restart on air

README.md

@@ -287,9 +287,9 @@ machine's fonts, so it looks the same on every machine.
 An overlay's own images and fonts, such as a logo or a brand face, come from
 `data:` URLs or from files in the scene file's directory, named relative to
 it (`url(brand/logo.png)`), never from the web or anywhere else on disk. The
-studio reads them all as the overlay starts, so its first frame has them, and
-a file changed on disk changes nothing on air until the overlay starts again,
-as when it is edited. Images are PNG or JPEG, at most 4096 pixels a side;
+studio reads them all as the overlay opens, so its first frame has them, and
+a file changed on disk changes nothing on air until the overlay opens again,
+as when it is edited; a restart on program reuses what it read. Images are PNG or JPEG, at most 4096 pixels a side;
 fonts are TrueType, OpenType, WOFF, or WOFF2, loaded with `@font-face`:
 
 ```css
@@ -318,8 +318,15 @@ element, attribute, rule, property, or asset it refused:
   draws more.
 
 An overlay's animation starts when the overlay does: when the studio opens
-it, and again whenever it is edited. One that no preview or program shows
-costs nothing until it is shown again, where its animation has carried on.
+it, and again whenever it is edited. It also starts over each time a scene
+showing it goes on program, as an item's keyframes do, so a lower third plays
+its entrance at every cut, and when a scene showing it goes into preview while
+program does not show it, so the preview shows the entrance too. Preview and
+program share its timeline, so a preview never restarts one program shows.
+Set `restart = false` (**Restart on program**, off, in the add form) for one
+that runs on across cuts, such as a clock or a ticker. One that no preview or
+program shows costs nothing until it is shown again, where its animation has
+carried on unless it restarts.
 Overlays publish no track of their own, so viewers see them only in the
 program.
 
@@ -512,6 +519,7 @@ height = 600
 kind = "overlay"
 width = 1920 # the overlay's own size, like a page's
 height = 1080
+restart = true # start over each time it goes on program, the default
 html = '''
 <style>
   .third { position: absolute; left: 80px; bottom: 120px; padding: 16px 32px;
@@ -583,7 +591,7 @@ Source kinds are `camera`, `display`, and `microphone` (each with an optional
 (macOS), `image` (PNG or JPEG), `media` (a video or audio file; see
 [Media files](#media-files)), `color` (`#rrggbb` or `#rrggbbaa`),
 `broadcast`, `browser` (a `url`, and a `width` and `height` up to 4096),
-`overlay` (its `html`, and a `width` and `height` up to 4096), `clone` (with the `source` it shows), `lut` (a 3D Adobe or Resolve `.cube`
+`overlay` (its `html`, a `width` and `height` up to 4096, and whether it `restart`s, true by default), `clone` (with the `source` it shows), `lut` (a 3D Adobe or Resolve `.cube`
 file, which no item places, but which grades what a `lut` filter names it in),
 and `replay`, where the Replay panel plays replays. The Devices panel fills in
 ids. `[[top]]` items make up the top layer.

quest/m1/README.md

@@ -24,7 +24,6 @@ than opening an m2 for them.
 ## Required
 
 - [Viewer-side composition](/quest/m1/compose/README.md) - sources as their own tracks plus a layout track, composed by viewers and by a server
-- [Overlays restart on air](/quest/m1/overlay-restart.md) - an overlay's CSS timeline restarts at each cut unless set to keep running
 - [Hotkeys and editor preferences](/quest/m1/hotkeys.md) - system-wide hotkeys, arrow nudge, aspect lock, and persisted editor settings
 - [Isolated guest recordings](/quest/m1/guest-recording.md) - record-each-source also writes each guest's tracks to its own file
 - [Scene graph view](/quest/m1/scene-graph.md) - a node view of picture and audio scenes, their routing, volume, pan, and waveforms

rs/moq-scene/src/collection.rs

@@ -743,7 +743,7 @@ pub struct Item {
 	/// Where on the canvas, stretched to fill it.
 	pub rect: Rect,
 	/// Whether the item is drawn. A hidden item keeps its place.
-	#[serde(default = "visible")]
+	#[serde(default = "yes")]
 	pub visible: bool,
 	/// Trimmed from what its source's crop leaves, before every filter.
 	#[serde(default, skip_serializing_if = "Crop::is_none")]
@@ -924,10 +924,14 @@ fn is_zero(value: &f32) -> bool {
 	*value == 0.0
 }
 
-fn visible() -> bool {
+fn yes() -> bool {
 	true
 }
 
+fn is_true(value: &bool) -> bool {
+	*value
+}
+
 /// What a source or item is drawn through, in order.
 ///
 /// Every filter is a pure function of the picture, so every host that composes
@@ -1497,6 +1501,12 @@ pub enum Source {
 		width: u32,
 		/// The overlay's viewport height in pixels.
 		height: u32,
+		/// Whether its CSS timeline starts over each time a scene showing it
+		/// goes on program, or into preview while program does not show it,
+		/// as keyframes do, rather than running on from when it opened, as a
+		/// clock should.
+		#[serde(default = "yes", skip_serializing_if = "is_true")]
+		restart: bool,
 	},
 	/// Another source's picture, captured once, with [`Collection::video`]
 	/// filters of its own. Its sound is not mixed a second time.
@@ -1769,6 +1779,18 @@ mod tests {
 				height: 800,
 			},
 		);
+		// Restarting is the default, written by leaving it out.
+		for (name, restart) in [("title", true), ("clock", false)] {
+			collection.sources.insert(
+				name.into(),
+				Source::Overlay {
+					html: "<h1>Live</h1>".into(),
+					width: 1920,
+					height: 1080,
+					restart,
+				},
+			);
+		}
 		collection.mixes = Mixes {
 			names: vec!["Stream".into(), "Recording".into()],
 			program: "Stream".into(),