Fix #4978: Area Type Options › Text Flow by rows or by columns

crates/doc/src/text/area.rs

@@ -29,6 +29,19 @@ impl VerticalAlign {
     }
 }
 
+/// Area Type Options › Text Flow: the order text fills the cells of area type with several rows
+/// and columns.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum TextFlow {
+    /// Down each column's rows, then on to the next column (the default, and what a document
+    /// from before the option reads as).
+    #[default]
+    Columns,
+    /// Across each row's columns, then on to the next row.
+    Rows,
+}
+
 /// Text Wrap Options of a wrap object (Object → Text Wrap).
 #[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
 #[serde(default)]
@@ -135,6 +148,9 @@ pub struct AreaOptions {
     pub first_baseline_min: f64,
     /// Vertical alignment of the lines in each row/column.
     pub vertical_align: VerticalAlign,
+    /// Text Flow: by columns (the default, left out when saved) or by rows.
+    #[serde(skip_serializing_if = "crate::skip::is_default")]
+    pub flow: TextFlow,
     /// How the frame and its text fit each other (Auto Size, Shrink Text to Fit).
     #[serde(skip_serializing_if = "crate::skip::is_default")]
     pub fit: AreaFit,
@@ -150,6 +166,7 @@ impl Default for AreaOptions {
             first_baseline: FirstBaseline::Ascent,
             first_baseline_min: 0.0,
             vertical_align: VerticalAlign::Top,
+            flow: TextFlow::Columns,
             fit: AreaFit::None,
         }
     }

crates/doc/src/text/tests.rs

@@ -293,6 +293,19 @@ fn paragraph_styles_split_merge_and_normalize() {
     assert_eq!(back.para_at(3).space_before, 4.0);
 }
 
+/// Text Flow is saved only when by rows: area type by columns (the default) saves as it did before
+/// the option, and files from before it read by columns; other values don't read.
+#[test]
+fn text_flow_is_saved_only_when_by_rows() {
+    let by_columns = serde_json::to_value(AreaOptions::default()).unwrap();
+    assert!(by_columns.get("flow").is_none());
+    assert_eq!(serde_json::from_value::<AreaOptions>(by_columns).unwrap().flow, TextFlow::Columns);
+    let by_rows = serde_json::to_value(AreaOptions { flow: TextFlow::Rows, ..AreaOptions::default() }).unwrap();
+    assert_eq!(by_rows["flow"], "rows");
+    assert_eq!(serde_json::from_value::<AreaOptions>(by_rows).unwrap().flow, TextFlow::Rows);
+    assert!(serde_json::from_value::<AreaOptions>(serde_json::json!({"flow": "diagonal"})).is_err());
+}
+
 /// 120 × 40 area type at (40, 40), its text drawn at twice its size.
 fn area_type() -> TextObject {
     let mut t = TextObject::point(Point::ZERO, "Some text", CharStyle::default());