G5: still footage layers are kept in the layer cache across times (#1812)

Footage layers had no layer cache key, so a still made a new layer buffer every frame on every
preview worker, and the GPU compositor uploaded it again each time (its upload cache is keyed
by buffer). Stills (without a proxy) are now keyed like text and shape layers, without the
source time; movies and sequences are unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/render/src/cache.rs

@@ -22,7 +22,7 @@ use std::hash::{Hash, Hasher};
 use std::sync::{Arc, Mutex};
 
 use effectcraft_effects::Buf;
-use effectcraft_project::{ItemKind, Layer, LayerSource, Node, PropGroup};
+use effectcraft_project::{FootageKind, ItemKind, Layer, LayerSource, Node, PropGroup};
 
 use crate::eval::EvalCtx;
 
@@ -481,7 +481,7 @@ fn hash_values(h: &mut KeyHasher, ctx: &EvalCtx, layer: &Layer, g: &PropGroup) {
 }
 
 /// Cache key for the processed (source → masks → effects) buffer of `layer` at the context
-/// time, or `None` when the layer must not be cached (footage, precomps, cameras, adjustment
+/// time, or `None` when the layer must not be cached (movie footage, precomps, cameras, adjustment
 /// layers…).
 pub fn layer_key(ctx: &EvalCtx, layer: &Layer, scale: f64, draft: bool, blur: bool) -> Option<u64> {
     // Time effects see property values at other times. Keyframes are part of the hashed
@@ -514,6 +514,13 @@ fn reads_other_times(layer: &Layer) -> bool {
         })
 }
 
+/// A still image (no proxy): its layer is cached like a text or shape layer, so the GPU
+/// compositor uploads it once, not every frame (#1812: four 21120 px plates re-uploaded by every
+/// preview worker ran the GPU out of memory). Movies and sequences stay in the media pool only.
+fn still_footage(ctx: &EvalCtx, item: effectcraft_project::ItemId) -> bool {
+    ctx.project.item(item).is_some_and(|it| it.proxy.is_none() && matches!(&it.kind, ItemKind::Footage(f) if f.kind == FootageKind::Still))
+}
+
 fn has_expression(g: &PropGroup) -> bool {
     g.children.iter().any(|c| match c {
         Node::Prop(p) => p.has_expression(),
@@ -552,14 +559,17 @@ fn key_any(ctx: &EvalCtx, layer: &Layer, scale: f64, draft: bool, blur: bool, fo
             hash_debug(&mut h, s);
         }
         LayerSource::Text | LayerSource::Shape => {}
-        LayerSource::Footage { item } if footage => {
+        LayerSource::Footage { item } if footage || still_footage(ctx, *item) => {
             let it = ctx.project.item(*item)?;
             let ItemKind::Footage(f) = &it.kind else { return None };
             hash_debug(&mut h, f);
             // A proxy (and its Use Proxy switch) changes the pixels.
             hash_debug(&mut h, &it.proxy);
             item.hash(&mut h);
-            ctx.source_time(layer).0.hash(&mut h);
+            // A still is the same at every time (unless a proxy, which may be a movie, stands in).
+            if f.kind != FootageKind::Still || it.proxy.is_some() {
+                ctx.source_time(layer).0.hash(&mut h);
+            }
             // Frame blending mixes neighbouring source frames.
             ctx.comp.enable_frame_blending.hash(&mut h);
         }

crates/render/src/tests_footage_size.rs

@@ -81,3 +81,28 @@ fn reduced_renders_take_footage_resampled_by_the_source() {
     Renderer::new(&p, &sized, RenderOpts { scale: 0.5, ..Default::default() }).comp_frame(cid, Tick::ZERO);
     assert!(sized.sizes.unwrap().into_inner().unwrap().is_empty());
 }
+
+/// #1812: a still's layer is kept in the layer cache across times (its texture then uploads to
+/// the GPU once, not every frame); a movie's is fetched again at every time.
+#[test]
+fn still_layers_are_cached_across_times_and_movies_are_not() {
+    for (kind, fetches) in [(FootageKind::Still, 1), (FootageKind::Video, 3)] {
+        let (mut p, cid) = project(BitDepth::Bpc8, false);
+        let Some(LayerSource::Footage { item }) = p.comp(cid).map(|c| c.layers[0].source.clone()) else { panic!("footage layer") };
+        if let Some(ItemKind::Footage(f)) = p.item_mut(item).map(|it| &mut it.kind) {
+            f.kind = kind;
+        }
+        let cache = crate::LayerCache::default();
+        let src = Clip { sizes: Some(Mutex::default()) };
+        let opts = RenderOpts { scale: 0.5, ..Default::default() };
+        for t in [0.0, 0.25, 0.5] {
+            let t = Tick::from_seconds_f64(t);
+            let mut r = Renderer::new(&p, &src, opts);
+            r.cache = Some(&cache);
+            let frame = r.comp_frame(cid, t);
+            assert_eq!(frame, Renderer::new(&p, &src, opts).comp_frame(cid, t), "{kind:?} at {t:?}");
+        }
+        // (each uncached render above fetches once more)
+        assert_eq!(src.sizes.unwrap().into_inner().unwrap().len(), fetches + 3, "{kind:?}");
+    }
+}