PPTX: a picture fill with no stretch or tile tiles (#290)

A shape or background blipFill with neither a:stretch nor a:tile (as some
tools write it, tdf#128596) was stretched across the shape; PowerPoint
tiles the picture at its own size.

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

crates/pptx/src/read/dml.rs

@@ -77,6 +77,12 @@ pub fn fill_el(imp: &mut Imp, part: &Part, f: &El) -> Option<Fill> {
         "solidFill" => Fill::Solid { color: color(f).unwrap_or(ColorRef::rgb(Rgba::BLACK)) },
         "gradFill" => Fill::Gradient(gradient(f)),
         "blipFill" => match blip_fill(imp, part, f) {
+            // A picture filling a shape or background with neither `a:stretch` nor `a:tile` is
+            // tiled at its own size, as PowerPoint draws it.
+            Some(mut p) if f.child("stretch").is_none() && f.child("tile").is_none() => {
+                p.mode = PictureMode::Tile { tx: 0.0, ty: 0.0, sx: 1.0, sy: 1.0, flip: "none".into(), align: "tl".into() };
+                Fill::Picture(p)
+            }
             Some(p) => Fill::Picture(p),
             None => Fill::None,
         },

crates/pptx/tests/fills.rs

@@ -0,0 +1,81 @@
+//! Fills read from decks written by other tools.
+
+use std::io::{Cursor, Read, Write};
+
+use deckcraft_geom::Xfrm;
+use deckcraft_model::style::{Fill, PictureFill, PictureMode};
+use deckcraft_model::{Shape, ShapeId, 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()
+}
+
+fn png() -> Vec<u8> {
+    let mut out = Cursor::new(vec![]);
+    image::DynamicImage::ImageRgb8(image::RgbImage::from_pixel(4, 4, image::Rgb([10, 200, 30])))
+        .write_to(&mut out, image::ImageFormat::Png)
+        .expect("png");
+    out.into_inner()
+}
+
+/// A deck with one shape filled with a stretched picture, exported.
+fn deck() -> Vec<u8> {
+    let mut p = defaults::new_presentation(None);
+    let media = p.add_media("tile.png", "image/png", png());
+    let id = ShapeId(p.alloc_id());
+    let first = p.slides[0].id;
+    p.slide_mut(first).expect("slide").shapes.push(Shape {
+        id,
+        name: "Textured".into(),
+        xfrm: Some(Xfrm::new(10.0, 10.0, 200.0, 100.0)),
+        fill: Some(Fill::Picture(PictureFill { media, ..Default::default() })),
+        ..Default::default()
+    });
+    deckcraft_pptx::export(&p).expect("export")
+}
+
+fn textured_mode(bytes: &[u8]) -> PictureMode {
+    let q = deckcraft_pptx::import(bytes).expect("import");
+    let s = q.slides[0].shapes.iter().find(|s| s.name == "Textured").expect("shape");
+    match &s.fill {
+        Some(Fill::Picture(pf)) => pf.mode.clone(),
+        other => panic!("{other:?}"),
+    }
+}
+
+#[test]
+fn a_shape_picture_fill_without_stretch_or_tile_tiles() {
+    // tdf#128596: `<a:blipFill><a:blip/></a:blipFill>` on a shape, as some tools write it;
+    // PowerPoint tiles the picture at its own size.
+    let bare = edit_slides(&deck(), |s| {
+        let s = regex_free_strip(&s, "<a:stretch>", "</a:stretch>");
+        assert!(!s.contains("<a:stretch"), "the test deck lost its stretch");
+        s
+    });
+    assert!(matches!(textured_mode(&bare), PictureMode::Tile { sx, sy, .. } if sx == 1.0 && sy == 1.0));
+    // An explicit stretch is still a stretch.
+    assert!(matches!(textured_mode(&deck()), PictureMode::Stretch { .. }));
+}
+
+/// `s` without the first `open`…`close` span inside a `blipFill`.
+fn regex_free_strip(s: &str, open: &str, close: &str) -> String {
+    let Some(b) = s.find("<a:blipFill") else { return s.to_string() };
+    let Some(i) = s[b..].find(open).map(|i| i + b) else { return s.to_string() };
+    let Some(j) = s[i..].find(close).map(|j| j + i + close.len()) else { return s.to_string() };
+    format!("{}{}", &s[..i], &s[j..])
+}