PPTX: a placeholder without geometry takes its layout's

PowerPoint leaves an inheriting placeholder's spPr without a geometry and
draws it with its layout (or master) placeholder's: a picture placeholder
cut into a shape, or with holes, keeps that shape on every slide. DeckCraft
read such placeholders as rectangles. They're now marked while reading
and given their parent's geometry once the layouts are read; anything
without a parent stays a rectangle. DeckCraft itself already writes
inheriting placeholders this way.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/pptx/src/read/mod.rs

@@ -14,7 +14,7 @@ use std::sync::Arc;
 use deckcraft_geom::{Size, emu_to_pt};
 use deckcraft_model::text::TextBody;
 use deckcraft_model::{
-    Background, Comment, CustomShow, HeaderFooter, Layout, LayoutId, LayoutType, Master, MasterId, MediaId, MediaItem, PhType, Presentation,
+    Background, Comment, CustomShow, Geom, HeaderFooter, Layout, LayoutId, LayoutType, Master, MasterId, MediaId, MediaItem, PhType, Presentation,
     Properties, Section, ShowSettings, Slide, SlideId, defaults,
 };
 
@@ -387,6 +387,7 @@ pub fn import(bytes: &[u8]) -> Result<Presentation, PptxError> {
         p.props.company = d.root.child("Company").map(|c| c.text()).unwrap_or_default();
     }
 
+    inherit_placeholder_geometry(&mut p);
     p.header_footer = header_footer(&p);
     p.media = std::mem::take(&mut imp.media);
     p.next_id = imp.next;
@@ -419,6 +420,91 @@ pub fn color_map(cm: &El) -> Vec<(String, String)> {
     cm.attrs.iter().filter(|(k, _)| !k.starts_with("xmlns")).map(|(k, v)| (k.clone(), v.clone())).collect()
 }
 
+/// Placeholders read without a geometry (an empty custom geometry, see `shapes::sp`) take the
+/// geometry of the layout or master placeholder they inherit from, as PowerPoint draws them: a
+/// layout's picture placeholder cut into a shape keeps that shape on the slide. Anything left
+/// is a rectangle.
+fn inherit_placeholder_geometry(p: &mut Presentation) {
+    let unset = |g: &Geom| matches!(g, Geom::Custom { paths } if paths.is_empty());
+    // Masters first, then layouts (from their masters), then slides (from layouts and masters).
+    for m in &mut p.masters {
+        let m = Arc::make_mut(m);
+        walk_shapes_mut(&mut m.shapes, &mut |s| {
+            if unset(&s.geom) {
+                s.geom = Geom::default();
+            }
+        });
+    }
+    let mut layout_geoms: Vec<(LayoutId, usize, Geom)> = vec![];
+    for m in &p.masters {
+        for l in &m.layouts {
+            let ctx = deckcraft_model::resolve::Ctx::for_layout(p, m, l);
+            for (i, s) in l.shapes.iter().enumerate() {
+                if unset(&s.geom) {
+                    let (_, mp) = deckcraft_model::resolve::parents(&ctx, s);
+                    layout_geoms.push((l.id, i, mp.map(|m| m.geom.clone()).filter(|g| !unset(g)).unwrap_or_default()));
+                }
+            }
+        }
+    }
+    for m in &mut p.masters {
+        let m = Arc::make_mut(m);
+        for l in &mut m.layouts {
+            for (id, i, g) in layout_geoms.iter().filter(|(id, _, _)| *id == l.id) {
+                let _ = id;
+                if let Some(s) = l.shapes.get_mut(*i) {
+                    s.geom = g.clone();
+                }
+            }
+        }
+    }
+    let mut slide_geoms: Vec<(usize, usize, Geom)> = vec![];
+    for (si, sl) in p.slides.iter().enumerate() {
+        let Some(ctx) = deckcraft_model::resolve::Ctx::for_slide(p, sl) else { continue };
+        for (i, s) in sl.shapes.iter().enumerate() {
+            if unset(&s.geom) {
+                let (lp, mp) = deckcraft_model::resolve::parents(&ctx, s);
+                let g = lp.map(|l| l.geom.clone()).filter(|g| !unset(g)).or_else(|| mp.map(|m| m.geom.clone()).filter(|g| !unset(g)));
+                slide_geoms.push((si, i, g.unwrap_or_default()));
+            }
+        }
+    }
+    for (si, i, g) in slide_geoms {
+        if let Some(sl) = p.slides.get_mut(si)
+            && let Some(s) = Arc::make_mut(sl).shapes.get_mut(i)
+        {
+            s.geom = g;
+        }
+    }
+    // Placeholders inside groups (rare) and anything still unset: rectangles.
+    for sl in &mut p.slides {
+        walk_shapes_mut(&mut Arc::make_mut(sl).shapes, &mut |s| {
+            if unset(&s.geom) {
+                s.geom = Geom::default();
+            }
+        });
+    }
+    for m in &mut p.masters {
+        for l in &mut Arc::make_mut(m).layouts {
+            walk_shapes_mut(&mut l.shapes, &mut |s| {
+                if unset(&s.geom) {
+                    s.geom = Geom::default();
+                }
+            });
+        }
+    }
+}
+
+/// Every shape, groups included.
+fn walk_shapes_mut(shapes: &mut [deckcraft_model::Shape], f: &mut dyn FnMut(&mut deckcraft_model::Shape)) {
+    for s in shapes {
+        f(s);
+        if let deckcraft_model::ShapeKind::Group { children, .. } = &mut s.kind {
+            walk_shapes_mut(children, f);
+        }
+    }
+}
+
 fn background(imp: &mut Imp, part: &Part, csld: &El) -> Option<Background> {
     let bg = csld.child("bg")?;
     if let Some(pr) = bg.child("bgPr") {

crates/pptx/src/read/shapes.rs

@@ -180,6 +180,15 @@ fn preset_geom(pg: &El) -> Geom {
     Geom::Preset { name, adj }
 }
 
+/// A placeholder whose `spPr` names no geometry takes its layout's (or master's) placeholder's:
+/// marked here with an empty custom geometry, filled in once the layouts are read
+/// (`inherit_placeholder_geometry`).
+fn mark_inherited_geometry(s: &mut Shape, pr: Option<&El>) {
+    if s.ph.is_some() && pr.is_none_or(|pr| pr.child("prstGeom").is_none() && pr.child("custGeom").is_none()) {
+        s.geom = Geom::Custom { paths: vec![] };
+    }
+}
+
 /// `spPr` → transform, geometry, fill, line, effects.
 fn sp_pr(imp: &mut Imp, part: &Part, s: &mut Shape, pr: &El) {
     if let Some(x) = pr.child("xfrm") {
@@ -229,6 +238,7 @@ fn sp(imp: &mut Imp, part: &Part, ctx: &mut IdCtx, e: &El) -> Shape {
     if let Some(pr) = e.child("spPr") {
         sp_pr(imp, part, &mut s, pr);
     }
+    mark_inherited_geometry(&mut s, e.child("spPr"));
     if e.bool("useBgFill") == Some(true) {
         s.fill = Some(Fill::Background);
     }

crates/pptx/tests/placeholders.rs

@@ -0,0 +1,64 @@
+//! Placeholder inheritance in decks written by PowerPoint.
+
+use std::io::{Cursor, Read, Write};
+
+use deckcraft_model::{Geom, defaults};
+
+/// `bytes` with `edit` applied to every slide part.
+fn edit_slides(bytes: &[u8], edit: impl Fn(String) -> String) -> Vec<u8> {
+    let mut z = zip::ZipArchive::new(Cursor::new(bytes)).expect("zip");
+    let mut out = zip::ZipWriter::new(Cursor::new(Vec::new()));
+    let o = zip::write::SimpleFileOptions::default();
+    for i in 0..z.len() {
+        let mut f = z.by_index(i).expect("entry");
+        let mut d = vec![];
+        f.read_to_end(&mut d).expect("read");
+        let name = f.name().to_string();
+        if name.starts_with("ppt/slides/slide") && name.ends_with(".xml") {
+            d = edit(String::from_utf8(d).expect("utf8")).into_bytes();
+        }
+        out.start_file(name, o).expect("start");
+        out.write_all(&d).expect("write");
+    }
+    out.finish().expect("finish").into_inner()
+}
+
+#[test]
+fn a_placeholder_without_geometry_takes_its_layouts() {
+    // PowerPoint leaves a slide placeholder's spPr empty and draws it with the layout
+    // placeholder's geometry (a picture placeholder cut into a shape keeps the shape).
+    let mut p = defaults::new_presentation(None);
+    let layout = p.slides[0].layout;
+    let m = std::sync::Arc::make_mut(&mut p.masters[0]);
+    let l = m.layouts.iter_mut().find(|l| l.id == layout).expect("layout");
+    for s in &mut l.shapes {
+        if s.ph.is_some() {
+            s.geom = Geom::Preset { name: "ellipse".into(), adj: vec![] };
+        }
+    }
+    let bytes = deckcraft_pptx::export(&p).expect("export");
+    // Strip the slide's own geometry, as PowerPoint writes inheriting placeholders.
+    let bare = edit_slides(&bytes, |s| {
+        let mut s = s;
+        while let Some(i) = s.find("<a:prstGeom") {
+            let Some(j) = s[i..].find("</a:prstGeom>").map(|j| j + i + "</a:prstGeom>".len()) else { break };
+            s.replace_range(i..j, "");
+        }
+        s
+    });
+    let q = deckcraft_pptx::import(&bare).expect("import");
+    let phs: Vec<_> = q.slides[0].shapes.iter().filter(|s| s.ph.is_some()).collect();
+    assert!(!phs.is_empty());
+    for s in phs {
+        assert!(matches!(&s.geom, Geom::Preset { name, .. } if name == "ellipse"), "{:?}", s.geom);
+    }
+    // A placeholder with its own geometry keeps it.
+    let first = p.slides[0].id;
+    for s in &mut p.slide_mut(first).expect("slide").shapes {
+        if s.ph.is_some() {
+            s.geom = Geom::Preset { name: "triangle".into(), adj: vec![] };
+        }
+    }
+    let q = deckcraft_pptx::import(&deckcraft_pptx::export(&p).expect("export")).expect("import");
+    assert!(q.slides[0].shapes.iter().filter(|s| s.ph.is_some()).all(|s| matches!(&s.geom, Geom::Preset { name, .. } if name == "triangle")));
+}