From 0d06481c341d27c0bea2090cc230582cee3a74ba Mon Sep 17 00:00:00 2001
From: Harrison Booth <73434116+Harrison-Booth@users.noreply.github.com>
Date: Mon, 2 Nov 2026 21:47:50 -0600
Subject: [PATCH] Preserve compatible line spacing in PPTX

---
 crates/model/src/resolve.rs       |  1 +
 crates/model/src/text.rs          |  2 ++
 crates/pptx/src/read/dml.rs       |  1 +
 crates/pptx/src/write/dml.rs      |  3 ++-
 crates/pptx/tests/it/roundtrip.rs | 21 +++++++++++++++++++++
 5 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/crates/model/src/resolve.rs b/crates/model/src/resolve.rs
index 8d87229f3..51f50b82d 100644
--- a/crates/model/src/resolve.rs
+++ b/crates/model/src/resolve.rs
@@ -249,6 +249,7 @@ pub fn body(ctx: &Ctx, shape: &Shape) -> BodyProps {
         rtl_col: Some(false),
         upright: Some(false),
         space_first_last: Some(false),
+        compat_ln_spc: None,
     });
     b
 }
diff --git a/crates/model/src/text.rs b/crates/model/src/text.rs
index 362f43939..0a7598f6e 100644
--- a/crates/model/src/text.rs
+++ b/crates/model/src/text.rs
@@ -121,6 +121,7 @@ pub struct BodyProps {
     pub upright: Option<bool>,
     /// Space before the first paragraph and after the last count too (`spcFirstLastPara`).
     pub space_first_last: Option<bool>,
+    pub compat_ln_spc: Option<bool>,
 }
 
 impl BodyProps {
@@ -144,6 +145,7 @@ impl BodyProps {
         self.rtl_col = self.rtl_col.or(p.rtl_col);
         self.upright = self.upright.or(p.upright);
         self.space_first_last = self.space_first_last.or(p.space_first_last);
+        self.compat_ln_spc = self.compat_ln_spc.or(p.compat_ln_spc);
     }
 }
 
diff --git a/crates/pptx/src/read/dml.rs b/crates/pptx/src/read/dml.rs
index a2ed6abe7..8ef3a68ba 100644
--- a/crates/pptx/src/read/dml.rs
+++ b/crates/pptx/src/read/dml.rs
@@ -358,6 +358,7 @@ pub fn body_pr(b: &El) -> BodyProps {
         rtl_col: b.bool("rtlCol"),
         upright: b.bool("upright"),
         space_first_last: b.bool("spcFirstLastPara"),
+        compat_ln_spc: b.bool("compatLnSpc"),
         ..Default::default()
     };
     for e in b.elements() {
diff --git a/crates/pptx/src/write/dml.rs b/crates/pptx/src/write/dml.rs
index 320810958..4de05d46f 100644
--- a/crates/pptx/src/write/dml.rs
+++ b/crates/pptx/src/write/dml.rs
@@ -468,7 +468,8 @@ pub fn body_pr(w: &mut W, b: &BodyProps) {
         .o("anchor", b.anchor.map(|a| a.xml()))
         .b("anchorCtr", b.anchor_ctr)
         .b("upright", b.upright)
-        .b("spcFirstLastPara", b.space_first_last);
+        .b("spcFirstLastPara", b.space_first_last)
+        .b("compatLnSpc", b.compat_ln_spc);
     let warp = b.warp.as_deref().filter(|s| !s.is_empty() && s.chars().all(|c| c.is_ascii_alphanumeric()));
     if warp.is_none() && b.autofit.is_none() {
         w.empty("a:bodyPr", a);
diff --git a/crates/pptx/tests/it/roundtrip.rs b/crates/pptx/tests/it/roundtrip.rs
index f651fc5c6..3c741f303 100644
--- a/crates/pptx/tests/it/roundtrip.rs
+++ b/crates/pptx/tests/it/roundtrip.rs
@@ -468,6 +468,27 @@ fn text_and_formatting_round_trip() {
     assert_eq!(run.text, "x=1");
 }
 
+#[test]
+fn compatible_line_spacing_mode_survives_two_pptx_round_trips() {
+    let mut p = Presentation::default();
+    let mut slide = new_slide(&mut p, "Compatible line spacing");
+    let mut enabled = shape(&mut p, "Enabled", 10.0, 10.0, 200.0, 80.0);
+    let mut enabled_body = TextBody::from_text("enabled");
+    enabled_body.body.compat_ln_spc = Some(true);
+    enabled.text = Some(enabled_body);
+    let mut disabled = shape(&mut p, "Disabled", 10.0, 100.0, 200.0, 80.0);
+    let mut disabled_body = TextBody::from_text("disabled");
+    disabled_body.body.compat_ln_spc = Some(false);
+    disabled.text = Some(disabled_body);
+    slide.shapes = vec![enabled, disabled];
+    p.slides.push(Arc::new(slide));
+
+    let twice = round(&round(&p));
+    let slide = twice.slides.last().expect("added slide");
+    assert_eq!(by_name(slide, "Enabled").text.as_ref().expect("text").body.compat_ln_spc, Some(true));
+    assert_eq!(by_name(slide, "Disabled").text.as_ref().expect("text").body.compat_ln_spc, Some(false));
+}
+
 #[test]
 fn shapes_fills_lines_effects_round_trip() {
     let p = rich_deck();