Render: memoized audio detection, bounded stretch, preroll, waveform, cache entries, 3D bounds, solids and selector time

comp_has_audio walked a precomp again for every layer using it; each comp
is answered once. A tiny stored stretch made one audio block fetch a vast
source range; playback speed is capped at 100x. Effect preroll is capped at
10 s. Waveforms stop where the audio ends and summarise at most a day.
Disk cache entries are decompressed only when their stated size matches
what their dimensions need (and at most 1 GiB). Advanced 3D triangle bounds
are clamped on both sides before narrowing. Solids larger than 16 Mpx are
made at a lower scale. A camera-facing layer's parent recursion is bounded.
A layer's Expression Selectors share one time allowance. A disk cache
folder under the temp folder is made private and may not be a link.

crates/render/src/audio.rs

@@ -24,6 +24,15 @@ use crate::{EvalCtx, ExprHost, FootageSource};
 
 const MAX_DEPTH: usize = 16;
 
+/// The fastest a layer's audio plays (a Stretch of 1%).
+const MAX_SPEED: f64 = 100.0;
+
+/// The most effect preroll (history before a block) mixed, in seconds, across a layer's effects.
+const MAX_PREROLL_SECONDS: f64 = 10.0;
+
+/// The longest footage a waveform summarises (a day).
+const MAX_PEAK_SECONDS: i64 = 24 * 3600;
+
 /// `frames` stereo sample frames of `comp`'s mix from comp time `start` at `rate` Hz,
 /// interleaved (L R L R …).
 pub fn mix_comp(project: &Project, footage: &dyn FootageSource, expr: Option<&dyn ExprHost>, comp: ItemId, start: Tick, frames: usize, rate: u32) -> Vec<f32> {
@@ -35,7 +44,19 @@ pub fn mix_comp(project: &Project, footage: &dyn FootageSource, expr: Option<&dy
 /// Whether the comp has anything audible (footage with audio, a sound generator, or a precomp
 /// that has).
 pub fn comp_has_audio(project: &Project, comp: ItemId) -> bool {
-    fn walk(project: &Project, comp: ItemId, depth: usize) -> bool {
+    // Each comp is answered once: a comp used by many layers at each of several levels was
+    // walked again for every use.
+    fn walk(project: &Project, comp: ItemId, depth: usize, seen: &mut std::collections::HashMap<ItemId, bool>) -> bool {
+        if let Some(&r) = seen.get(&comp) {
+            return r;
+        }
+        // In progress: a cycle back into it adds nothing.
+        seen.insert(comp, false);
+        let r = walk_once(project, comp, depth, seen);
+        seen.insert(comp, r);
+        r
+    }
+    fn walk_once(project: &Project, comp: ItemId, depth: usize, seen: &mut std::collections::HashMap<ItemId, bool>) -> bool {
         let Some(c) = project.comp(comp) else { return false };
         depth < MAX_DEPTH
             && c.layers.iter().any(|l| {
@@ -45,12 +66,12 @@ pub fn comp_has_audio(project: &Project, comp: ItemId) -> bool {
                             LayerSource::Footage { item } => {
                                 matches!(project.item(*item).map(|i| &i.kind), Some(ItemKind::Footage(f)) if f.has_audio && !f.missing)
                             }
-                            LayerSource::Comp { item } => walk(project, *item, depth + 1),
+                            LayerSource::Comp { item } => walk(project, *item, depth + 1, seen),
                             _ => false,
                         })
             })
     }
-    walk(project, comp, 0)
+    walk(project, comp, 0, &mut std::collections::HashMap::new())
 }
 
 /// Enabled audio effects of a layer (in stack order) with their effect ids.
@@ -155,7 +176,9 @@ impl MixEnv<'_> {
             return out;
         }
         let m = b - a;
-        let speed = 100.0 / l.stretch;
+        // A tiny stretch would fetch a vast source range for one block: past MAX_SPEED the layer
+        // plays at that speed.
+        let speed = (100.0 / l.stretch).min(MAX_SPEED);
         let src_n = ((m as f64 * speed).ceil() as usize).max(1);
         let lt = l.layer_time(sample_tick(i0 + a as i64, rate));
         let buf = match &l.source {
@@ -211,7 +234,7 @@ impl MixEnv<'_> {
             return self.layer_raw(l, i0, n, false);
         }
         let reversed = fx.iter().any(|(id, _, _)| audio_fx::reverses(id));
-        let pre_s: f64 = fx.iter().map(|(id, _, p)| audio_fx::preroll(id, p)).sum();
+        let pre_s: f64 = fx.iter().map(|(id, _, p)| audio_fx::preroll(id, p)).sum::<f64>().clamp(0.0, MAX_PREROLL_SECONDS);
         let pre = (pre_s * self.rate as f64).ceil() as usize;
         let b0 = i0 - pre as i64;
         let mut buf = self.layer_raw(l, b0, n + pre, reversed);
@@ -339,12 +362,14 @@ pub fn footage_peaks(footage: &dyn FootageSource, item: ItemId, f: &effectcraft_
     let bin = (64usize).max(4000 / bins_per_sec as usize);
     let rate = bin as u32 * bins_per_sec;
     let chunk = bin * bins_per_sec as usize;
-    let total = units_ceil(duration, rate).max(0) as usize;
+    // The stated duration comes from the project: at most a day is summarised, and the summary
+    // ends where the audio does.
+    let total = units_ceil(duration, rate).clamp(0, MAX_PEAK_SECONDS.saturating_mul(rate as i64)) as usize;
     let mut out = Vec::with_capacity(total / bin + 1);
     let mut i = 0usize;
     while i < total {
         let n = chunk.min(total - i);
-        let buf = footage.audio(item, f, sample_tick(i as i64, rate), n, rate).unwrap_or_else(|| vec![0.0; n * 2]);
+        let Some(buf) = footage.audio(item, f, sample_tick(i as i64, rate), n, rate) else { break };
         out.extend(peak_summary(&buf, bin));
         i += n;
     }
@@ -372,6 +397,28 @@ mod tests {
         }
     }
 
+    #[test]
+    fn audio_detection_answers_each_comp_once() {
+        // Twenty levels, each comp holding two layers of the one below: 2^20 walks without a
+        // memo, and all silent. A cycle is answered too.
+        let mut p = Project::default();
+        let mk = |p: &mut Project, layers: Vec<Layer>| {
+            let mut c = Comp::new(8, 8, FrameRate::new(25, 1), Tick::from_seconds_f64(1.0));
+            c.layers = layers.into();
+            p.add_item("C", effectcraft_color::Label::Sandstone, None, ItemKind::Comp(c.into()))
+        };
+        let base = Comp::new(8, 8, FrameRate::new(25, 1), Tick::from_seconds_f64(1.0));
+        let mut below = mk(&mut p, vec![]);
+        for _ in 0..20 {
+            let a = build::layer(&mut p, &base, "a", LayerSource::Comp { item: below }, (0, 0), None);
+            let b = build::layer(&mut p, &base, "b", LayerSource::Comp { item: below }, (0, 0), None);
+            below = mk(&mut p, vec![a, b]);
+        }
+        let (tx, rx) = std::sync::mpsc::channel();
+        std::thread::spawn(move || tx.send(comp_has_audio(&p, below)).ok());
+        assert!(!rx.recv_timeout(std::time::Duration::from_secs(20)).expect("detection finishes"));
+    }
+
     #[test]
     fn mixes_layers_with_levels_and_in_out() {
         let mut p = Project::default();

crates/render/src/disk_cache.rs

@@ -299,12 +299,36 @@ pub fn default_folder() -> PathBuf {
     if let Some(x) = std::env::var_os("XDG_CACHE_HOME") {
         return PathBuf::from(x).join("effectcraft/disk-cache");
     }
-    home.map(|h| h.join(".cache/effectcraft/disk-cache")).unwrap_or_else(|| std::env::temp_dir().join("effectcraft-disk-cache"))
+    // Without a home folder: a per-user folder in the shared temp folder, made private by `open`.
+    let user = std::env::var("USER").or_else(|_| std::env::var("USERNAME")).unwrap_or_default();
+    home.map(|h| h.join(".cache/effectcraft/disk-cache")).unwrap_or_else(|| std::env::temp_dir().join(format!("effectcraft-disk-cache-{user}")))
+}
+
+/// A cache folder in the shared temp folder must be ours alone: not a link someone placed there,
+/// and private (setting the mode fails unless we own it), so another user cannot redirect the
+/// cache's writes and clean-up or read its files.
+#[cfg(unix)]
+fn make_private(folder: &Path) -> std::io::Result<()> {
+    use std::os::unix::fs::PermissionsExt;
+    if !folder.starts_with(std::env::temp_dir()) {
+        return Ok(());
+    }
+    if std::fs::symlink_metadata(folder)?.file_type().is_symlink() {
+        return Err(std::io::Error::new(std::io::ErrorKind::PermissionDenied, "the disk cache folder is a link"));
+    }
+    std::fs::set_permissions(folder, std::fs::Permissions::from_mode(0o700))
+}
+
+#[cfg(not(unix))]
+fn make_private(_: &Path) -> std::io::Result<()> {
+    Ok(())
 }
 
 impl DiskCache {
     /// Open (or create) the cache in `folder`, holding at most `max_bytes`.
     pub fn open(folder: impl AsRef<Path>, max_bytes: u64) -> std::io::Result<Arc<DiskCache>> {
+        std::fs::create_dir_all(folder.as_ref())?;
+        make_private(folder.as_ref())?;
         let dir = folder.as_ref().join(VERSION);
         std::fs::create_dir_all(&dir)?;
         let dc = Arc::new(DiskCache {
@@ -624,7 +648,7 @@ impl DiskCache {
     /// A segmentation (chain key, scale) written by [`DiskCache::put_seg`].
     pub fn get_seg(&self, key: u64, scale: f64) -> Option<effectcraft_effects::roto::FrameSeg> {
         let p = self.read(Kind::Matte, seg_key(key, scale))?;
-        let raw = lz4_flex::decompress_size_prepended(&p).ok()?;
+        let raw = decompress_checked(&p, None)?;
         effectcraft_effects::roto::FrameSeg::from_bytes(&raw)
     }
 
@@ -778,13 +802,28 @@ fn encode_frame(w: u32, h: u32, rgba: &[u8]) -> Vec<u8> {
     out
 }
 
+/// The most bytes one cache entry decompresses to (a 16384² frame of 8-bit RGBA): the size an
+/// entry states is checked against it, and against what the entry's dimensions need, before
+/// anything is allocated.
+const MAX_ENTRY_BYTES: usize = 1 << 30;
+
+/// An LZ4 payload with its stated size prepended, decompressed only when that size is
+/// `expected` (any size up to [`MAX_ENTRY_BYTES`] when `None`).
+fn decompress_checked(p: &[u8], expected: Option<usize>) -> Option<Vec<u8>> {
+    let size = u32::from_le_bytes(p.get(..4)?.try_into().ok()?) as usize;
+    if size > MAX_ENTRY_BYTES || expected.is_some_and(|e| e != size) {
+        return None;
+    }
+    lz4_flex::decompress(p.get(4..)?, size).ok()
+}
+
 fn decode_frame(p: &[u8]) -> Option<Frame8> {
     if p.len() < 8 {
         return None;
     }
     let w = u32::from_le_bytes(p[0..4].try_into().ok()?);
     let h = u32::from_le_bytes(p[4..8].try_into().ok()?);
-    let rgba = lz4_flex::decompress_size_prepended(&p[8..]).ok()?;
+    let rgba = decompress_checked(&p[8..], Some((w as usize).checked_mul(h as usize)?.checked_mul(4)?))?;
     (rgba.len() == w as usize * h as usize * 4).then_some(Frame8 { width: w, height: h, rgba })
 }
 
@@ -820,8 +859,8 @@ fn decode_layer(p: &[u8]) -> Option<Buf> {
     let f = |i: usize| -> Option<f64> { Some(f64::from_le_bytes(p[i..i + 8].try_into().ok()?)) };
     let offset = [f(8)?, f(16)?];
     let scale = f(24)?;
-    let planes = lz4_flex::decompress_size_prepended(&p[32..]).ok()?;
-    let n = w as usize * h as usize;
+    let n = (w as usize).checked_mul(h as usize)?;
+    let planes = decompress_checked(&p[32..], Some(n.checked_mul(16)?))?;
     if planes.len() != n * 16 {
         return None;
     }
@@ -980,6 +1019,35 @@ pub fn frame_key(content: u128, frame: i64, scale_milli: u32, view: u64) -> u128
 mod tests {
     use super::*;
 
+    #[cfg(unix)]
+    #[test]
+    fn a_cache_folder_in_the_temp_folder_is_made_private_and_never_a_link() {
+        use std::os::unix::fs::PermissionsExt;
+        let d = tmpdir("private");
+        let dc = DiskCache::open(&d, 1 << 20).unwrap();
+        assert_eq!(std::fs::metadata(&d).unwrap().permissions().mode() & 0o777, 0o700);
+        drop(dc);
+        let link = tmpdir("link");
+        std::os::unix::fs::symlink(&d, &link).unwrap();
+        assert!(DiskCache::open(&link, 1 << 20).is_err());
+        let _ = std::fs::remove_file(&link);
+        let _ = std::fs::remove_dir_all(&d);
+    }
+
+    #[test]
+    fn an_entry_stating_a_size_its_dimensions_do_not_need_is_not_decompressed() {
+        // A 2×2 frame whose payload states 3 GiB: refused before any allocation.
+        let mut p = 2u32.to_le_bytes().to_vec();
+        p.extend_from_slice(&2u32.to_le_bytes());
+        p.extend_from_slice(&(3u32 << 30).to_le_bytes());
+        p.extend_from_slice(&[0; 16]);
+        assert!(decode_frame(&p).is_none());
+        assert!(decompress_checked(&p[8..], None).is_none());
+        // A well-formed entry still decodes.
+        let ok = encode_frame(2, 2, &[7; 16]);
+        assert_eq!(decode_frame(&ok).map(|f| f.rgba), Some(vec![7; 16]));
+    }
+
     fn tmpdir(name: &str) -> PathBuf {
         let d = std::env::temp_dir().join(format!("effectcraft-disk-cache-{name}-{}", std::process::id()));
         let _ = std::fs::remove_dir_all(&d);

crates/render/src/pipeline.rs

@@ -36,6 +36,9 @@ pub struct MediaOverride {
     pub(crate) item: ItemId,
 }
 
+/// The most pixels a solid layer's buffer holds (as the other layer buffers are held to).
+const MAX_SOLID_PIXELS: f64 = 16.0e6;
+
 impl MediaOverride {
     /// A Media Replacement of `layer`'s footage by `item`.
     pub fn new(layer: LayerId, item: ItemId) -> Self {
@@ -690,6 +693,10 @@ impl<'a> Renderer<'a> {
         match &layer.source {
             LayerSource::Solid { item } => {
                 let ItemKind::Solid(sol) = &self.project.item(*item)?.kind else { return None };
+                // One colour: a solid larger than MAX_SOLID_PIXELS is made at a lower scale (the
+                // buffer carries it) instead of allocating gigabytes for a uniform plane.
+                let area = (sol.width as f64 * s) * (sol.height as f64 * s);
+                let s = if area > MAX_SOLID_PIXELS { s * (MAX_SOLID_PIXELS / area).sqrt() } else { s };
                 let w = ((sol.width as f64 * s).ceil() as u32).max(1);
                 let h = ((sol.height as f64 * s).ceil() as u32).max(1);
                 if layer.switches.adjustment {

crates/render/src/text.rs

@@ -244,12 +244,21 @@ pub fn animator_selection(ctx: &EvalCtx, layer: &Layer, anim: &PropGroup, lay: &
             "expressionSelector" => {
                 let Some(prop) = sel.get("amount") else { continue };
                 let stat = ctx.v3(layer, sel, "amount", [100.0; 3]);
+                // One allowance for the whole layer: the expression runs per character, each run
+                // with its own time limit, so a slow expression on a long text is stopped once it
+                // has failed or the layer's evaluations pass MAX_SELECTOR_TIME.
+                let start = web_time::Instant::now();
+                let stopped = std::cell::Cell::new(false);
                 Box::new(move |i, n, prev| {
                     let pv = prev.map(|x| x * 100.0);
                     // Without an expression engine: the static amount scales the selection.
                     let fallback = [0, 1, 2].map(|d| stat[d] * prev[d]);
-                    let r = match ctx.expr.filter(|_| prop.has_expression()) {
-                        Some(h) => h.eval_text_selector(ctx, layer, prop, i, n, pv).unwrap_or(fallback),
+                    let live = !stopped.get() && start.elapsed() < MAX_SELECTOR_TIME;
+                    let r = match ctx.expr.filter(|_| live && prop.has_expression()) {
+                        Some(h) => h.eval_text_selector(ctx, layer, prop, i, n, pv).unwrap_or_else(|_| {
+                            stopped.set(true);
+                            fallback
+                        }),
                         None => fallback,
                     };
                     r.map(|x| (x / 100.0).clamp(-1.0, 1.0))
@@ -275,6 +284,8 @@ pub fn animator_selection(ctx: &EvalCtx, layer: &Layer, anim: &PropGroup, lay: &
     acc
 }
 
+/// The most time one layer's Expression Selectors may take across all its characters.
+const MAX_SELECTOR_TIME: std::time::Duration = std::time::Duration::from_secs(2);
 /// Evaluate animators for every glyph.
 pub fn char_transforms(ctx: &EvalCtx, layer: &Layer, text: &PropGroup, lay: &TextLayout) -> Vec<CharXf> {
     let mut out = vec![CharXf::default(); lay.glyphs.len()];

crates/render/src/three_d/adv/raster.rs

@@ -126,11 +126,14 @@ fn setup(s: &Scene, clip: &[[f32; 4]], range: std::ops::Range<usize>) -> Vec<STr
                 x1 = x1.max(v.0[0]);
                 y1 = y1.max(v.0[1]);
             }
+            // Clamped on both sides to the viewport before narrowing to i32, so a far-off
+            // coordinate cannot wrap into a huge pixel range.
+            let (w, h) = (s.width as i64, s.height as i64);
             let bbox = [
-                (x0.floor() as i64).max(0) as i32,
-                (y0.floor() as i64).max(0) as i32,
-                (x1.ceil() as i64).min(s.width as i64) as i32,
-                (y1.ceil() as i64).min(s.height as i64) as i32,
+                (x0.floor() as i64).clamp(0, w) as i32,
+                (y0.floor() as i64).clamp(0, h) as i32,
+                (x1.ceil() as i64).clamp(0, w) as i32,
+                (y1.ceil() as i64).clamp(0, h) as i32,
             ];
             if bbox[0] >= bbox[2] || bbox[1] >= bbox[3] {
                 continue;

crates/render/src/three_d/camera.rs

@@ -299,6 +299,13 @@ pub fn auto_orient_2d(ctx: &EvalCtx, layer: &Layer) -> f64 {
     path_tangent(ctx, layer).map(|t| t.y.atan2(t.x).to_degrees()).unwrap_or(0.0)
 }
 
+/// The most camera-facing layers whose parents are evaluated inside one another.
+const MAX_ORIENT_NESTING: usize = 8;
+
+thread_local! {
+    static ORIENT_NESTING: std::cell::Cell<usize> = const { std::cell::Cell::new(0) };
+}
+
 /// Whether `id` is `layer` or one of its parents.
 fn in_parent_chain(ctx: &EvalCtx, layer: &Layer, id: effectcraft_project::LayerId) -> bool {
     let mut cur = Some(layer);
@@ -333,8 +340,18 @@ pub fn auto_orient_3d(ctx: &EvalCtx, layer: &Layer, pos: Vec3) -> Option<Mat4> {
             if ctx.comp.active_camera(ctx.time).is_some_and(|c| in_parent_chain(ctx, c, layer.id)) {
                 return None;
             }
+            // The parent's world matrix evaluates the parent's own orientation: a parent cycle
+            // of camera-facing layers would recurse without end, and a chain of them is walked
+            // again from every link. Past MAX_ORIENT_NESTING the layer keeps its Orientation.
+            let nesting = ORIENT_NESTING.with(|n| n.get());
+            if nesting >= MAX_ORIENT_NESTING {
+                return None;
+            }
+            ORIENT_NESTING.with(|n| n.set(nesting + 1));
+            let parent = parent_world(ctx, layer);
+            ORIENT_NESTING.with(|n| n.set(nesting));
             let eye = active_camera(ctx).eye;
-            let e = parent_world(ctx, layer).inverse().unwrap_or(Mat4::IDENTITY).apply(eye);
+            let e = parent.inverse().unwrap_or(Mat4::IDENTITY).apply(eye);
             let d = pos - e;
             (d.length() > 1e-9).then(|| basis_rotation(d, vec3(0.0, 1.0, 0.0)))
         }