M12: a space at the end of a line doesn't count when fitting XFA text

Words keep the space after them, and the line-fit test counted it, so a
label written with a trailing space wrapped when its box was a fraction
of a point narrower than the label plus that space: DA Form 31's 'a.
DATE ' and 'b. TIME ' put their second word on top of the field below.
A line now fits by what it draws, and alignment ignores every trailing
space, not just one.

crates/xfa/src/tests.rs

@@ -2067,3 +2067,49 @@ fn som_indices_count_earlier_same_named_siblings() {
     let sibs = SomIndices::of(&children);
     assert_eq!((0..=children.len()).map(|i| sibs.at(i)).collect::<Vec<_>>(), [0, 0, 1, 0, 2, 1, 0]);
 }
+
+/// A draw `w` points wide holding `text` in Arial 10 pt, aligned `h_align`.
+fn one_draw(text: &str, w: f64, h_align: &str) -> String {
+    format!(
+        r##"<xdp:xdp xmlns:xdp="http://ns.adobe.com/xdp/"><template xmlns="http://www.xfa.org/schema/xfa-template/3.3/">
+<subform name="form" layout="tb">
+ <pageSet><pageArea name="front"><contentArea x="0.5in" y="0.5in" w="7.5in" h="10in"/><medium short="8.5in" long="11in"/></pageArea></pageSet>
+ <draw name="label" w="{w}pt" h="0.5in"><value><text>{text}</text></value><font typeface="Arial" size="10pt"/><para hAlign="{h_align}"/></draw>
+</subform>
+</template></xdp:xdp>"##
+    )
+}
+
+/// The text spans of the only page, with their baselines.
+fn draw_spans(xdp: &str) -> Vec<text::Span> {
+    layout_xml(xdp).unwrap().pages[0].items.iter().filter_map(|i| if let Item::Text(s) = i { Some(s.clone()) } else { None }).collect()
+}
+
+#[test]
+fn a_space_at_the_end_of_a_line_does_not_count_when_fitting_it() {
+    // The box is just wide enough for "a. DATE"; the label is written "a. DATE " (as forms
+    // often are). The trailing space is never drawn, so the label stays on one line.
+    let w = pdfcraft_fonts::helvetica_width("a. DATE", 10.0) + 0.01;
+    let spans = draw_spans(&one_draw("a. DATE ", w, "left"));
+    let baselines: std::collections::BTreeSet<i64> = spans.iter().map(|s| (s.baseline * 100.0).round() as i64).collect();
+    assert_eq!(baselines.len(), 1, "{spans:?}");
+    // Several spaces after it don't count either.
+    let spans = draw_spans(&one_draw("a. DATE   ", w, "left"));
+    let baselines: std::collections::BTreeSet<i64> = spans.iter().map(|s| (s.baseline * 100.0).round() as i64).collect();
+    assert_eq!(baselines.len(), 1, "{spans:?}");
+    // Text that is wider than the box still wraps.
+    let spans = draw_spans(&one_draw("a. DATES ", w, "left"));
+    let baselines: std::collections::BTreeSet<i64> = spans.iter().map(|s| (s.baseline * 100.0).round() as i64).collect();
+    assert_eq!(baselines.len(), 2, "{spans:?}");
+}
+
+#[test]
+fn trailing_spaces_do_not_shift_centered_or_right_aligned_text() {
+    let w = 200.0;
+    let ink = pdfcraft_fonts::helvetica_width("TITLE", 10.0);
+    let left_edge = |align: &str, text: &str| draw_spans(&one_draw(text, w, align)).first().map(|s| s.x).unwrap();
+    // The draw's left edge is the content area's (0.5in); centered and right-aligned text is
+    // placed by its drawn width, whatever spaces follow it.
+    assert!((left_edge("center", "TITLE   ") - (36.0 + (w - ink) / 2.0)).abs() < 1e-6);
+    assert!((left_edge("right", "TITLE   ") - (36.0 + w - ink)).abs() < 1e-6);
+}

crates/xfa/src/text.rs

@@ -145,6 +145,13 @@ struct Word {
 }
 
 /// Break the runs of a paragraph into words (spaces stay attached to the word before them).
+/// The width of `w` without the spaces it ends with: what it takes at the end of a line, where
+/// a space is never drawn.
+fn ink_width(w: &Word) -> f64 {
+    let ink = w.text.trim_end_matches(' ');
+    if ink.len() == w.text.len() { w.width } else { w.face.width(ink) }
+}
+
 fn words(runs: &[Run], base: &Face, embed: &dyn Fn(&str) -> String) -> Vec<Word> {
     let mut out = Vec::new();
     for run in runs {
@@ -197,12 +204,14 @@ pub fn layout(rich: &RichText, rect: Rect, para: &Para, base: &Face, embed: &dyn
         let mut first_in_para = true;
         let indent = |first: bool| if first { para.text_indent.max(0.0) } else { 0.0 };
         for w in ws {
-            let fits = line.width + w.width <= avail - indent(line.first) || line.words.is_empty() && w.width <= avail - indent(line.first);
+            // A word fits when what it draws does: the spaces after it would end the line.
+            let ink = ink_width(&w);
+            let fits = line.width + ink <= avail - indent(line.first) || line.words.is_empty() && ink <= avail - indent(line.first);
             if !fits && !line.words.is_empty() {
                 let done = std::mem::replace(&mut line, Line { words: Vec::new(), width: 0.0, size: base.size, first: false });
                 lines.push((done, p.h_align));
             }
-            if w.width > avail - indent(line.first) && line.words.is_empty() {
+            if ink > avail - indent(line.first) && line.words.is_empty() {
                 // A word longer than a line: break it by character.
                 let mut piece = String::new();
                 for ch in w.text.chars() {
@@ -248,8 +257,16 @@ pub fn layout(rich: &RichText, rect: Rect, para: &Para, base: &Face, embed: &dyn
     let mut y = start_y + para.space_above;
     for ((line, align), lh) in lines.into_iter().zip(heights) {
         let indent = if line.first { para.text_indent.max(0.0) } else { 0.0 };
-        // Trailing spaces don't count for alignment.
-        let trailing = line.words.last().map_or(0.0, |w| if w.text.ends_with(' ') { w.face.width(" ") } else { 0.0 });
+        // Trailing spaces don't count for alignment: those of the last word with ink, and any
+        // words of spaces alone after it.
+        let mut trailing = 0.0;
+        for w in line.words.iter().rev() {
+            let ink = ink_width(w);
+            trailing += w.width - ink;
+            if !w.text.trim_end_matches(' ').is_empty() {
+                break;
+            }
+        }
         let used = (line.width - trailing).max(0.0);
         let mut x = rect.x + para.margin_left + indent;
         x += match align.unwrap_or(para.h_align) {