Map the WMF window onto the placeable box (#2673)

crates/metafile/src/import/wmf.rs

@@ -99,6 +99,13 @@ fn window(bytes: &[u8], mut at: usize) -> Option<Rect> {
     Some(Rect::new(o.x, o.y, o.x + e.x, o.y + e.y).abs())
 }
 
+/// Logical → document for a placeable file whose window (`org`, `ext`) is mapped onto its box `b`;
+/// a negative extent flips that axis, as in GDI.
+fn window_map(b: Rect, k: f64, org: Point, ext: Point) -> Affine {
+    let ratio = |box_len: f64, e: f64| if e.abs() > 1e-12 { box_len / e } else { 1.0 };
+    Affine::scale_non_uniform(k * ratio(b.width(), ext.x), k * ratio(b.height(), ext.y)) * Affine::translate(-org.to_vec2())
+}
+
 pub(super) fn play(bytes: &[u8]) -> Result<Imported, String> {
     let (start, placeable) = header(bytes).ok_or("the WMF header is damaged")?;
     let (frame, inch) = match placeable {
@@ -109,6 +116,9 @@ pub(super) fn play(bytes: &[u8]) -> Result<Imported, String> {
     let origin = frame.map_or(Point::ZERO, |f| f.origin());
     let artboard = frame.map_or(Rect::new(0.0, 0.0, 1.0, 1.0), |f| Rect::new(0.0, 0.0, f.width() * k, f.height() * k));
     let mut p = Player::new(Kind::Wmf, Affine::scale(k) * Affine::translate(-origin.to_vec2()), 25.4 / inch, artboard);
+    // With a placeable header, the window records map the window onto the box.
+    let placed = placeable.map(|(b, _)| b).filter(|b| b.width() > 0.0 && b.height() > 0.0);
+    let mut win = (placed.map_or(Point::ZERO, |b| b.origin()), placed.map_or(Point::ZERO, |b| Point::new(b.width(), b.height())));
     let mut at = start;
     let mut ended = false;
     while let Some(head) = bytes.get(at..at + 6) {
@@ -122,7 +132,16 @@ pub(super) fn play(bytes: &[u8]) -> Result<Imported, String> {
         if !matches!(function, 0x0213 | 0x0214) {
             p.flush();
         }
-        if record(&mut p, function, rec.get(6..).unwrap_or_default()).is_none() {
+        if let (Some(b), 0x020B | 0x020C) = (placed, function) {
+            if let Some(v) = point_yx(&mut Reader::new(rec.get(6..).unwrap_or_default())) {
+                if function == 0x020B {
+                    win.0 = v;
+                } else {
+                    win.1 = v;
+                }
+                p.dev_to_doc = window_map(b, k, win.0, win.1);
+            }
+        } else if record(&mut p, function, rec.get(6..).unwrap_or_default()).is_none() {
             p.skip();
         }
         at += rec.len();

crates/metafile/src/tests_import.rs

@@ -289,6 +289,25 @@ fn hand_built_wmf_plays_like_gdi() {
     assert_eq!(fill_rgb(&p[1]), Some([0, 255, 0]), "the new brush took the freed slot");
 }
 
+#[test]
+fn wmf_window_is_mapped_onto_the_placeable_box() {
+    // The box is 1000 × 500 units at 1440 an inch: 50 × 25 pt.
+    let want = Rect::new(12.5, 6.25, 37.5, 18.75);
+    // Window 0,0 – 4000 × 2000: the rectangle 1000,500 – 3000,1500 is the middle half.
+    let ext = vec![(0x020C, le16(&[2000, 4000])), (0x041B, le16(&[1500, 3000, 500, 1000]))];
+    // Window 10000,20000 – 1000 × 500 (the box): the rectangle 10250,20125 – 10750,20375.
+    let org = vec![(0x020B, le16(&[20000, 10000])), (0x020C, le16(&[500, 1000])), (0x041B, le16(&[20375, 10750, 20125, 10250]))];
+    // Window 0,2000 – 4000 × -2000 (y up): the same rectangle, flipped onto the same place.
+    let flip = vec![(0x020B, le16(&[2000, 0])), (0x020C, le16(&[-2000, 4000])), (0x041B, le16(&[1500, 3000, 500, 1000]))];
+    for records in [ext, org, flip] {
+        let back = import(&hand_wmf(1000, 500, &records)).unwrap();
+        assert!(near(back.document.artboards[0].rect, Rect::new(0.0, 0.0, 50.0, 25.0), 1e-9));
+        let p = paths(&back.document);
+        assert_eq!(p.len(), 1);
+        assert!(near(p[0].geometric_bounds().unwrap(), want, 1e-6), "{:?}", p[0].geometric_bounds());
+    }
+}
+
 #[test]
 fn damaged_files_fail_or_import_partly() {
     let good = emf(&sample()).bytes;