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

crates/text/src/layout/driver.rs

@@ -18,6 +18,7 @@ pub fn layout(db: &FontDb, t: &TextObject) -> TextLayout {
         first_baseline: a.first_baseline,
         first_baseline_min: a.first_baseline_min,
         vertical_align: a.vertical_align,
+        flow: a.flow,
         fit: a.fit,
         ..LayoutOptions::default()
     };

crates/text/src/layout/region.rs

@@ -142,9 +142,13 @@ impl Region {
         let cw = ((bbox.width() - gutter * (cols - 1) as f64) / cols as f64).max(0.0);
         let rh = ((bbox.height() - gutter * (rows - 1) as f64) / rows as f64).max(0.0);
         let mut out = Vec::with_capacity(rows * cols);
-        // Text flows down each column, then across (Illustrator's default "by columns").
-        for c in 0..cols {
-            for r in 0..rows {
+        // Text Flow: down each column, then across (by columns, the default), or across each row,
+        // then down (by rows).
+        let by_rows = opts.flow == vectorcraft_doc::TextFlow::Rows;
+        let (outer, inner) = if by_rows { (rows, cols) } else { (cols, rows) };
+        for o in 0..outer {
+            for i in 0..inner {
+                let (r, c) = if by_rows { (o, i) } else { (i, o) };
                 let x0 = bbox.x0 + c as f64 * (cw + gutter);
                 let y0 = bbox.y0 + r as f64 * (rh + gutter);
                 let cell = if rows * cols == 1 { bbox } else { Rect::new(x0, y0, x0 + cw, y0 + rh) };

crates/text/src/lib.rs

@@ -47,7 +47,7 @@ use kurbo::{Affine, BezPath, Point, Rect, Shape, Vec2};
 pub use layout::{decorations, fit_first_line, layout, layout_with, scaled};
 pub use vectorcraft_doc::TextObject;
 
-pub use vectorcraft_doc::{AreaFit, FirstBaseline, VerticalAlign};
+pub use vectorcraft_doc::{AreaFit, FirstBaseline, TextFlow, VerticalAlign};
 
 /// Paragraph composer; stored per text object in [`vectorcraft_doc::ParaStyle::composer`].
 pub use vectorcraft_doc::Composer;
@@ -56,7 +56,7 @@ pub use vectorcraft_doc::Composer;
 /// composer, OpenType features). [`layout`] takes rows/columns/inset/first baseline from the object.
 #[derive(Clone, Debug, PartialEq)]
 pub struct LayoutOptions {
-    /// Area type rows and columns (text flows down each column, then across). Layout clamps each
+    /// Area type rows and columns (text fills them in [`LayoutOptions::flow`] order). Layout clamps each
     /// count to 1..=[`vectorcraft_doc::AreaOptions::MAX_ROWS_COLUMNS`].
     pub rows: usize,
     pub columns: usize,
@@ -69,6 +69,8 @@ pub struct LayoutOptions {
     pub first_baseline_min: f64,
     /// Vertical alignment of the lines in each row/column (Area Type Options "Align").
     pub vertical_align: VerticalAlign,
+    /// Area Type Options "Text Flow": by columns (down each column, then across) or by rows.
+    pub flow: TextFlow,
     /// Area type only: Shrink Text to Fit scales overflowing text down at layout time (see
     /// [`TextLayout::fit_scale`]); the other fits are the engine's business and lay out as `None`.
     pub fit: AreaFit,
@@ -87,6 +89,7 @@ impl Default for LayoutOptions {
             first_baseline: FirstBaseline::Ascent,
             first_baseline_min: 0.0,
             vertical_align: VerticalAlign::Top,
+            flow: TextFlow::Columns,
             fit: AreaFit::None,
             composer: None,
             features: OtFeatures::default(),

crates/text/src/tests/typo.rs

@@ -457,6 +457,26 @@ fn hit_testing_picks_the_right_column() {
     }
 }
 
+/// Area Type Options › Text Flow (#4978): by columns (the default) the second cell is the one
+/// below the first; by rows it is the one beside it.
+#[test]
+fn text_flow_fills_the_cells_by_columns_or_by_rows() {
+    let t = area(&COPY.repeat(8), style(12.0), Rect::new(0.0, 0.0, 420.0, 300.0), Justify::Left);
+    let grid = LayoutOptions { rows: 2, columns: 2, gutter: 20.0, ..Default::default() };
+    for (flow, second) in [(TextFlow::Columns, (0.0, 160.0)), (TextFlow::Rows, (220.0, 0.0))] {
+        let l = layout_with(db(), &t, &LayoutOptions { flow, ..grid.clone() });
+        let frame = l.frames.get(1).copied().unwrap();
+        assert_eq!((frame.x0, frame.y0), second, "{flow:?}");
+        let line = l.lines.iter().find(|li| li.region == 1).expect("text reaches the second cell");
+        assert!(line.x0 >= second.0 - 1e-6 && line.baseline >= second.1, "{flow:?}: {line:?}");
+        assert!(l.lines.iter().all(|li| l.lines.iter().all(|m| m.region >= li.region || m.start <= li.start)), "{flow:?}: text runs in cell order");
+    }
+    // The object's own option lays out the same way.
+    let mut by_rows = t.clone();
+    (by_rows.area.rows, by_rows.area.columns, by_rows.area.gutter, by_rows.area.flow) = (2, 2, 20.0, TextFlow::Rows);
+    assert_eq!(layout(db(), &by_rows).frames.get(1).map(|f| (f.x0, f.y0)), Some((220.0, 0.0)));
+}
+
 // ---------- area flow ----------
 
 #[test]