Merge pull request #1561 from Hamza0101/fix/rtl-first-line-indent

A right-to-left paragraph's first-line indent is at its right edge (#1448)

crates/compose/src/lib.rs

@@ -1676,10 +1676,16 @@ fn compose_with_db(doc: &Document, story: &Story, frames: &[FrameSpec], opts: &C
                 }
                 // A drop cap sits at the start-side indent; the first-line indent doesn't move it.
                 let beside = drop_cap.as_ref().filter(|dc| line_no < dc.lines && col_first_line == 0).map(DropCap::indent);
+                let first_line = if line_no == 0 { pp.first_line_indent } else { 0.0 };
                 let (ind_l, ind_r) = match beside {
                     Some(w) if rtl => (pp.left_indent, pp.right_indent + w),
                     Some(w) => (pp.left_indent + w, pp.right_indent),
-                    None => (pp.left_indent + if line_no == 0 { pp.first_line_indent } else { 0.0 }, pp.right_indent),
+                    // The first-line indent is at the paragraph's start side, which is the right
+                    // one in a right-to-left paragraph: applied on the left it moved the line the
+                    // wrong way, out of the frame for the hanging indent a numbered list uses
+                    // (#1448).
+                    None if rtl => (pp.left_indent, pp.right_indent + first_line),
+                    None => (pp.left_indent + first_line, pp.right_indent),
                 };
                 let lx0 = x0 + ind_l;
                 let lx1 = x1 - ind_r;

crates/compose/src/tests.rs

@@ -7323,3 +7323,45 @@ fn parent_page_frames_know_which_side_of_the_spine_they_are_on() {
     assert!(frame_specs(&d, left_story)[0].left_page);
     assert!(!frame_specs(&d, right_story)[0].left_page);
 }
+
+/// A right-to-left paragraph's first-line indent belongs at its start side, the right. Applied on
+/// the left it moved the first line the wrong way — out of the frame for the hanging indent a
+/// numbered list uses (right indent 10 mm, first line −10 mm), while the wrapped lines sat where
+/// the first line should have been (#1448).
+#[test]
+fn an_rtl_first_line_indent_is_at_the_right_edge() {
+    const MM: f64 = 72.0 / 25.4;
+    // Latin text in a right-to-left paragraph: the direction is the paragraph's, and it is the
+    // placement that is being measured, so no Arabic font has to be present.
+    let text = LOREM;
+    let rect = Rect::new(0.0, 0.0, 200.0, 300.0);
+    let para = |dir, align, first, left, right| ParaAttrs {
+        direction: Some(dir),
+        align: Some(align),
+        first_line_indent: Some(first),
+        left_indent: Some(left),
+        right_indent: Some(right),
+        ..Default::default()
+    };
+    // The hanging indent of a numbered list, right to left.
+    let (d, sid, _) = doc_with(text, rect, para(designcraft_doc::TextDirection::RightToLeft, Align::Right, -10.0 * MM, 0.0, 10.0 * MM));
+    let cs = compose_story(&d, sid, &ComposeOptions::default());
+    let lines = all_lines(&cs);
+    assert!(lines.len() >= 2, "the text wraps: {}", lines.len());
+    let right_edge = |l: &Line| l.glyphs.iter().filter(|g| g.visible).map(|g| g.x + g.adv).fold(f64::MIN, f64::max);
+    let left_edge = |l: &Line| l.glyphs.iter().filter(|g| g.visible).map(|g| g.x).fold(f64::MAX, f64::min);
+    // The first line reaches the frame's right edge; the wrapped lines stop 10 mm short of it.
+    assert!((right_edge(lines[0]) - rect.x1).abs() < 1.0, "first line at the edge: {}", right_edge(lines[0]));
+    assert!((right_edge(lines[1]) - (rect.x1 - 10.0 * MM)).abs() < 1.0, "wrapped line indented: {}", right_edge(lines[1]));
+    // And nothing leaves the frame on the left, which is where the first line used to go.
+    for (i, l) in lines.iter().enumerate() {
+        assert!(left_edge(l) >= rect.x0 - 0.01, "line {i} starts inside the frame: {}", left_edge(l));
+    }
+
+    // The same paragraph left to right is unchanged: the first line hangs on the left.
+    let (d, sid, _) = doc_with(text, rect, para(designcraft_doc::TextDirection::LeftToRight, Align::Left, -10.0 * MM, 10.0 * MM, 0.0));
+    let cs = compose_story(&d, sid, &ComposeOptions::default());
+    let lines = all_lines(&cs);
+    assert!((left_edge(lines[0]) - rect.x0).abs() < 1.0, "left to right, first line at the edge: {}", left_edge(lines[0]));
+    assert!((left_edge(lines[1]) - (rect.x0 + 10.0 * MM)).abs() < 1.0, "left to right, wrapped line indented: {}", left_edge(lines[1]));
+}