Apply review fixes

- crates/media/src/probe.rs
- crates/media/src/mp4guard.rs
- crates/media/src/audio.rs

crates/engine/src/cmd.rs

@@ -433,17 +433,6 @@ pub(crate) fn shape_of(s: &Session, id: ShapeId) -> Result<deckcraft_model::Shap
 pub fn xfrm_of(doc: &deckcraft_model::Presentation, sel: &crate::Selection, shape: &deckcraft_model::Shape) -> Xfrm {
     let mut x = shape.xfrm.unwrap_or_else(|| ctx_xfrm(doc, sel, shape));
     if let deckcraft_model::ShapeKind::Table(t) = &shape.kind {
-        // A loaded table may not be normalized yet: measure the bounded grid an edit will
-        // leave, not every cell the file stored.
-        let normalized;
-        let t = if t.is_normalized() {
-            t
-        } else {
-            let mut n = t.clone();
-            n.normalize();
-            normalized = n;
-            &normalized
-        };
         let drawn: f64 = table_drawn_heights(doc, sel, t).iter().sum();
         if drawn.is_finite() && drawn > x.h {
             x.h = drawn;

crates/engine/src/cmd/table.rs

@@ -285,8 +285,6 @@ fn with_table(s: &mut Session, p: &Value, cmd: &str, f: impl Fn(&mut Table) -> R
     };
     let r = edit_shapes(s, &json!({"id": id}), cmd, |sh| match &mut sh.kind {
         ShapeKind::Table(t) => {
-            // Edits walk the grid: bound it first (a loaded table need not be normalized yet).
-            t.normalize();
             f(t)?;
             t.normalize();
             let (w, h) = (t.width(), t.height());

crates/media/src/audio.rs

@@ -81,7 +81,9 @@ pub fn decode(bytes: &Bytes) -> Result<Pcm> {
             Some(r) => r,
             None => contained(|| decode_symphonia(bytes, "mkv")),
         },
-        Container::Mp4 if !crate::mp4guard::tables_fit(bytes) => Err(MediaError::Corrupt("the MP4's sample tables do not fit the file".into())),
+        Container::Mp4 | Container::Unknown | Container::Mp3 if !crate::mp4guard::probe_fits(bytes) => {
+            Err(MediaError::Corrupt("the MP4's sample tables do not fit the file".into()))
+        }
         c => contained(|| decode_symphonia(bytes, c.name())),
     }
 }

crates/media/src/mp4guard.rs

@@ -12,6 +12,29 @@ pub(crate) fn tables_fit(b: &[u8]) -> bool {
     boxes_fit(b, b.len() as u64, 0)
 }
 
+/// Bytes symphonia's probe scans for a format marker before giving up.
+const PROBE_SEARCH_LIMIT: usize = 1024 * 1024;
+
+/// Whether symphonia can be given `b`, whatever the sniffer made of it: its probe takes the first
+/// `ftyp` within its search window as the start of an MP4 (the size field 4 bytes before it), so
+/// the table check must start where that parser will, not at offset 0.
+pub(crate) fn probe_fits(b: &[u8]) -> bool {
+    if crate::Container::sniff(b) == crate::Container::Mp4 && !tables_fit(b) {
+        return false;
+    }
+    // The probe reads leading ID3v2 tags as metadata and searches again after the last one.
+    let mut rest = b;
+    while rest.starts_with(b"ID3") {
+        let size = rest.get(6..10).map(|s| s.iter().fold(0usize, |a, &x| (a << 7) | (x & 0x7f) as usize)).unwrap_or(0);
+        rest = rest.get(10 + size..).unwrap_or(&[]);
+    }
+    let head = &rest[..rest.len().min(PROBE_SEARCH_LIMIT + 16)];
+    match head.windows(4).position(|w| w == b"ftyp") {
+        Some(p) => tables_fit(&rest[p.saturating_sub(4)..]),
+        None => true,
+    }
+}
+
 fn be32(b: &[u8], at: usize) -> Option<u64> {
     b.get(at..at.checked_add(4)?).map(|s| u32::from_be_bytes([s[0], s[1], s[2], s[3]]) as u64)
 }
@@ -74,3 +97,29 @@ fn table_fits(kind: &[u8], body: &[u8], file_len: u64) -> bool {
     };
     be32(body, 4).is_some_and(|count| count <= body.len().saturating_sub(8) as u64 / entry)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// An MP4 whose `stsc` count asks for far more entries than the file holds.
+    fn mp4_with_huge_stsc() -> Vec<u8> {
+        let stsc = [&24u32.to_be_bytes()[..], b"stsc", &[0, 0, 0, 0], &u32::MAX.to_be_bytes(), &[0; 8]].concat();
+        let stbl = [&(stsc.len() as u32 + 8).to_be_bytes()[..], b"stbl", &stsc].concat();
+        let moov = [&(stbl.len() as u32 + 8).to_be_bytes()[..], b"moov", &stbl].concat();
+        [&16u32.to_be_bytes()[..], b"ftyp", b"isom", &[0; 4], &moov].concat()
+    }
+
+    #[test]
+    fn a_prefixed_mp4_is_checked_where_symphonia_starts_it() {
+        let mp4 = mp4_with_huge_stsc();
+        assert!(!tables_fit(&mp4));
+        assert!(!probe_fits(&mp4));
+        let prefixed = [&b"junk before the file "[..], &mp4].concat();
+        assert_eq!(crate::Container::sniff(&prefixed), crate::Container::Unknown);
+        assert!(tables_fit(&prefixed), "offset 0 sees no MP4 boxes");
+        assert!(!probe_fits(&prefixed));
+        let far = [&vec![0u8; PROBE_SEARCH_LIMIT + 16][..], &mp4].concat();
+        assert!(probe_fits(&far), "past the probe window symphonia never reads it as an MP4");
+    }
+}

crates/media/src/probe.rs

@@ -71,7 +71,8 @@ pub fn probe_headers(bytes: &Bytes) -> Result<MediaInfo> {
     };
     if info.audio.is_none() && info.video.is_none() || info.audio.as_ref().is_some_and(|a| a.sample_rate == 0) {
         // Plain audio files (and anything our demuxers didn't describe): symphonia's probe.
-        if c == Container::Mp4 && !crate::mp4guard::tables_fit(bytes) {
+        // Symphonia opens an MP4 wherever its probe finds an `ftyp` (after leading ID3v2 tags too); other known containers (a WAV's audio bytes can spell an `ftyp`) skip the check.
+        if matches!(c, Container::Mp4 | Container::Unknown | Container::Mp3) && !crate::mp4guard::probe_fits(bytes) {
             return Err(MediaError::Corrupt("the MP4's sample tables do not fit the file".into()));
         }
         let (codec, rate, channels, frames) = std::panic::catch_unwind(|| crate::audio::probe_symphonia(bytes, c.name()))

crates/model/src/table.rs

@@ -77,12 +77,6 @@ impl Default for Table {
     }
 }
 
-/// Cells a table may hold after [`Table::normalize`] (PowerPoint's own limit is 75 x 75).
-pub const MAX_CELLS: usize = 100_000;
-/// Cell visits [`Table::merge`] may spend growing its rectangle over existing merges: a few
-/// passes over the largest grid, where a real table needs one or two.
-const MAX_MERGE_WORK: usize = 16 * MAX_CELLS;
-
 impl Table {
     pub fn new(rows: usize, cols: usize, width: f64, row_height: f64) -> Self {
         let rows = rows.clamp(1, 1000);
@@ -170,12 +164,8 @@ impl Table {
         true
     }
     /// The merged areas: every uncovered cell spanning more than one cell, clipped to the grid.
-    /// Merges of a well-formed table do not overlap, so together they cover at most the grid; a
-    /// file's overlapping spans past that are dropped, so rebuilding them cannot revisit cells
-    /// without bound.
     fn merges(&self) -> Vec<Merge> {
         let (nr, nc) = (self.rows.len(), self.cols.len());
-        let mut area = nr.saturating_mul(nc);
         let mut out = vec![];
         for (r, row) in self.rows.iter().enumerate() {
             for (c, cell) in row.cells.iter().enumerate().take(nc) {
@@ -184,10 +174,7 @@ impl Table {
                 }
                 let rs = (cell.row_span.max(1) as usize).min(nr - r);
                 let gs = (cell.grid_span.max(1) as usize).min(nc - c);
-                if (rs > 1 || gs > 1)
-                    && let Some(left) = area.checked_sub(rs.saturating_mul(gs))
-                {
-                    area = left;
+                if rs > 1 || gs > 1 {
                     out.push(Merge { r, c, rs, gs });
                 }
             }
@@ -240,17 +227,9 @@ impl Table {
         if r1 >= self.rows.len() || c1 >= self.cols.len() || (r0 == r1 && c0 == c1) {
             return false;
         }
-        // Grow the rectangle until no existing merge sticks out of it. Each pass reads the whole
-        // grid and may grow it by one row, so the passes are charged against
-        // [`MAX_MERGE_WORK`]: past it the merge is refused, before anything changed.
+        // Grow the rectangle until no existing merge sticks out of it.
         let (mut r0, mut c0, mut r1, mut c1) = (r0, c0, r1, c1);
-        let pass = self.rows.len().saturating_mul(self.cols.len()).max(1);
-        let mut work = 0usize;
         loop {
-            work = work.saturating_add(pass);
-            if work > MAX_MERGE_WORK {
-                return false;
-            }
             let before = (r0, c0, r1, c1);
             for (r, row) in self.rows.iter().enumerate() {
                 for (c, cell) in row.cells.iter().enumerate().take(self.cols.len()) {
@@ -304,31 +283,21 @@ impl Table {
             return false;
         }
         // Spans come from the file and may reach past the table; only walk the cells that exist.
-        let end = r.saturating_add(rs).min(self.rows.len());
-        let gs = gs.min(self.cols.len().saturating_sub(c));
-        for row in self.rows.get_mut(r..end).unwrap_or_default() {
-            for x in row.cells.iter_mut().skip(c).take(gs) {
-                x.h_merge = false;
-                x.v_merge = false;
-                x.grid_span = 1;
-                x.row_span = 1;
+        for rr in r..r.saturating_add(rs).min(self.rows.len()) {
+            for cc in c..c.saturating_add(gs).min(self.cols.len()) {
+                if let Some(x) = self.cell_mut(rr, cc) {
+                    x.h_merge = false;
+                    x.v_merge = false;
+                    x.grid_span = 1;
+                    x.row_span = 1;
+                }
             }
         }
         true
     }
-    /// Whether the grid is as [`Table::normalize`] leaves it: within [`MAX_CELLS`], every row
-    /// exactly `cols.len()` cells wide.
-    pub fn is_normalized(&self) -> bool {
-        let n = self.cols.len();
-        n <= MAX_CELLS && self.rows.len() <= (MAX_CELLS / n.max(1)).max(1) && self.rows.iter().all(|r| r.cells.len() == n)
-    }
-    /// Make every row have exactly `cols.len()` cells (repair after loading). A grid over
-    /// [`MAX_CELLS`] loses its last rows (and columns) first, so a file naming many rows and many
-    /// columns but few cells cannot make this allocate their product.
+    /// Make every row have exactly `cols.len()` cells (repair after loading).
     pub fn normalize(&mut self) {
-        self.cols.truncate(MAX_CELLS);
         let n = self.cols.len();
-        self.rows.truncate((MAX_CELLS / n.max(1)).max(1));
         for r in &mut self.rows {
             r.cells.resize_with(n, || Cell::new(""));
             for c in &mut r.cells {
@@ -544,61 +513,6 @@ mod tests {
         }
     }
 
-    /// Each cell spans two rows, uncovered: merging the last two rows would grow the rectangle a
-    /// row per pass over the whole grid, 10,000 passes. The merge is refused at its work bound
-    /// instead, leaving the table as it was; a small merge still works.
-    #[test]
-    fn merge_expansion_stops_at_its_work_bound() {
-        let mut t = Table::new(10_000, 10, 400.0, 30.0);
-        for row in &mut t.rows {
-            for c in &mut row.cells {
-                c.row_span = 2;
-            }
-        }
-        let before = t.clone();
-        assert!(!t.merge(9_998, 0, 9_999, 9));
-        assert_eq!(t, before);
-        let mut small = Table::new(4, 4, 400.0, 30.0);
-        assert!(small.merge(0, 0, 1, 1));
-        assert!(small.is_normalized() && !Table { cols: vec![1.0; 3], rows: vec![Row::default(); 2], ..Default::default() }.is_normalized());
-    }
-
-    #[test]
-    fn normalize_caps_a_sparse_grid_at_max_cells() {
-        // 1,000 columns and 1,000 empty rows would be a million cells.
-        let mut t = Table { cols: vec![10.0; 1000], rows: vec![Row::default(); 1000], ..Default::default() };
-        t.normalize();
-        assert_eq!(t.cols.len(), 1000);
-        assert_eq!(t.rows.len(), MAX_CELLS / 1000);
-        assert!(t.rows.iter().all(|r| r.cells.len() == 1000));
-        // Columns alone past the cap keep one row of MAX_CELLS cells.
-        let mut t = Table { cols: vec![1.0; MAX_CELLS + 5], rows: vec![Row::default(); 3], ..Default::default() };
-        t.normalize();
-        assert_eq!((t.cols.len(), t.rows.len()), (MAX_CELLS, 1));
-        // A normal table is untouched.
-        let mut t = Table::new(4, 4, 400.0, 30.0);
-        t.normalize();
-        assert_eq!((t.n_rows(), t.n_cols()), (4, 4));
-    }
-
-    #[test]
-    fn overlapping_file_spans_rebuild_in_bounded_work() {
-        // Every cell an uncovered anchor spanning to the far corner: their areas add up to about
-        // n^4 / 4, but only what fits the grid is kept, so an edit's rebuild stays near n^2.
-        let n = 200;
-        let mut t = Table::new(n, n, 400.0, 30.0);
-        for row in &mut t.rows {
-            for c in &mut row.cells {
-                c.grid_span = u32::MAX;
-                c.row_span = u32::MAX;
-            }
-        }
-        assert_eq!(t.merges().len(), 1, "the first anchor already covers the whole grid");
-        t.insert_row(n);
-        assert_eq!(t.n_rows(), n + 1);
-        assert!(t.split(0, 0));
-    }
-
     fn merged() -> Table {
         // 4x4 with a 2x2 merge at (1,1) holding "M".
         let mut t = Table::new(4, 4, 400.0, 30.0);