M7: keep a preceding paragraph out of a shared text object's marker (#2517)

A partial rewrite of the last paragraph opened the marker at the shared BT, so the paragraph before it was inside the region.

crates/edit/src/tests.rs

@@ -2982,6 +2982,31 @@ fn a_partial_rewrite_inside_one_text_object_keeps_the_neighbour() {
     }
 }
 
+/// The last paragraph of a shared text object has no neighbour after it. The marker still has
+/// to open after the preceding paragraph, not at the shared `BT`, or that paragraph joins it.
+#[test]
+fn a_partial_rewrite_of_the_last_paragraph_in_one_text_object_keeps_the_one_before_it() {
+    let src =
+        "BT /F1 12 Tf 14.4 TL 1 0 0 1 72 700 Tm (Alpha first row.) Tj T* (Alpha next row.) Tj T* T* (Neighbor stays.) Tj T* (Neighbor next.) Tj ET";
+    let mut doc = text_page(src);
+    let texts = |doc: &Document| text::text_blocks(doc, 0).unwrap().into_iter().map(|b| b.text).collect::<Vec<_>>();
+    assert_eq!(texts(&doc), ["Alpha first row. Alpha next row.", "Neighbor stays. Neighbor next."], "the blank line is a paragraph break");
+    text::replace_block(&mut doc, 0, 1, "Neighbor stays.\nChanged.").unwrap();
+    let content = page_content(&doc);
+    assert_eq!(texts(&doc), ["Alpha first row. Alpha next row.", "Neighbor stays. Changed."], "{content}");
+    let alpha = content.find("(Alpha first row.)").expect("the preceding paragraph");
+    let open = content.find("/P BMC").expect("marker");
+    assert!(alpha < open, "the marker swallowed the preceding paragraph: {content}");
+    let neighbour = content.find("(Neighbor stays.)").expect("the kept row");
+    assert!(open < neighbour, "the kept row is outside the marker: {content}");
+    for saved in [reopen(&doc), Document::open(Arc::new(write_full(&doc, &SaveOptions::default()).unwrap())).unwrap()] {
+        assert_eq!(texts(&saved), ["Alpha first row. Alpha next row.", "Neighbor stays. Changed."], "save joined the preceding paragraph");
+        let mut again = saved;
+        text::replace_block(&mut again, 0, 1, "Neighbor stays.\nEdited.").unwrap();
+        assert_eq!(texts(&reopen(&again)), ["Alpha first row. Alpha next row.", "Neighbor stays. Edited."]);
+    }
+}
+
 /// #2516's published steps: adding a row must not make the next edit-by-number rewrite Charlie.
 /// The issue also asks for a stable paragraph id. That is #2508, and this test does not add one.
 #[test]

crates/edit/src/text_regions/styled.rs

@@ -677,13 +677,27 @@ fn paragraph_marker(block: &TextBlock, lines: &[TextLine], ops: &[Op]) -> Option
         .filter(|(index, _)| !belongs.contains(index))
         .filter_map(|(_, line)| line.ops.iter().copied().filter(|op| *op > end).min())
         .min();
+    let open = block.lines.iter().filter_map(|i| lines.get(*i)).flat_map(|line| line.ops.iter().copied()).min()?;
     if let Some(op) = neighbour.filter(|op| *op < after_text) {
-        let open = block.lines.iter().filter_map(|i| lines.get(*i)).flat_map(|line| line.ops.iter().copied()).min()?;
         // `BT` stays outside the marker. Both ends are inside the one text object.
         if open > start {
             return Some((open, None, op));
         }
     }
+    // The last paragraph of a shared text object has no neighbour after it. Opening at the
+    // shared `BT` would take the preceding paragraph into the marker. Open at this paragraph's
+    // first operator instead, and close before the shared `ET`, so both ends stay inside it.
+    let preceding =
+        lines.iter().enumerate().filter(|(index, _)| !belongs.contains(index)).any(|(_, line)| line.ops.iter().any(|op| *op > start && *op < open));
+    if preceding {
+        if let Some(et) = after_text.checked_sub(1).filter(|index| ops.get(*index).is_some_and(|op| op.op.as_slice() == b"ET"))
+            && open > start
+            && open < et
+        {
+            return Some((open, None, et));
+        }
+        return None;
+    }
     // `None` is the next-line index: the close is after this paragraph's `ET`, not at the
     // following line's `BT`.
     Some((start, None, after_text))

parity/acrobat-features.toml

@@ -1914,8 +1914,8 @@ milestone = "M7"
 status = "shipped"
 commands = ["edit.edit_text"]
 tools = ["text_paragraphs"]
-evidence = ["crates/edit/src/tests.rs::paragraphs_are_found_and_rewrapped", "crates/edit/src/tests.rs::a_wrapped_list_item_keeps_its_continuation_and_the_items_after_it", "crates/edit/src/tests.rs::a_blank_line_keeps_the_next_paragraph", "crates/edit/src/tests.rs::a_grown_paragraph_does_not_swallow_the_next_one", "crates/automation/tests/it/automation.rs::a_blank_line_stays_a_separate_paragraph_through_tools", "crates/automation/tests/it/automation.rs::paragraph_grouping_survives_save_and_reopen_through_tools", "crates/edit/src/tests.rs::a_partial_rewrite_of_the_only_paragraph_stays_one_block", "crates/edit/src/tests.rs::a_partial_rewrite_closes_before_the_operator_that_follows_the_paragraph", "crates/edit/src/tests.rs::a_partial_rewrite_of_the_last_marked_paragraph_stays_inside_its_region", "crates/edit/src/tests.rs::a_partial_rewrite_keeps_the_next_marked_region_closed", "crates/edit/src/tests.rs::a_partial_rewrite_of_an_unmarked_paragraph_leaves_the_marked_neighbour_closed", "crates/edit/src/tests.rs::a_partial_rewrite_inside_one_marked_region_leaves_the_neighbour_inside_it", "crates/edit/src/tests.rs::a_partial_rewrite_inside_one_text_object_keeps_the_neighbour", "crates/automation/tests/it/automation.rs::a_partial_rewrite_of_the_last_paragraph_stays_one_through_tools", "crates/edit/src/tests.rs::text_lines_are_found_and_replaced_in_place", "crates/ui-egui/tests/it/editing.rs::editing_existing_text_in_place", "crates/automation/tests/it/automation.rs::editing_existing_text_through_tools"]
-notes = "lines grouped into paragraphs by stream, font, size, left alignment and regular baseline spacing; a blank line (about twice the paragraph's own leading) stays a separate paragraph, and editing the first one leaves the next in place (#2517). An explicit TL is that leading. Without one, Td does not set it: three or more rows at one repeated step stay one paragraph, and a single wider gap stays a break. A rewrite marks the whole paragraph, including a row it leaves in the source, so adding a row does not absorb the next paragraph on a later edit. When the paragraph is the last text on the page, that marker closes after the paragraph's last ET, so a kept source row stays inside it. When the next paragraph shares that text object, the marker opens after BT and closes before the neighbour's text. The extra marker is not added when the paragraph is already one marked region and the next line is in a different region. Hyphenated line ends are joined. A row opening with a list marker starts its own item, and the row a list item wraps onto continues it at its hanging indent, so editing one item never takes the items after it. Still open: a larger heading joined to smaller body lines (#1756) and cells in different columns (#1680, #2478). Two rows and no third step still cannot be told from a paragraph break when there is no TL."
+evidence = ["crates/edit/src/tests.rs::paragraphs_are_found_and_rewrapped", "crates/edit/src/tests.rs::a_wrapped_list_item_keeps_its_continuation_and_the_items_after_it", "crates/edit/src/tests.rs::a_blank_line_keeps_the_next_paragraph", "crates/edit/src/tests.rs::a_grown_paragraph_does_not_swallow_the_next_one", "crates/automation/tests/it/automation.rs::a_blank_line_stays_a_separate_paragraph_through_tools", "crates/automation/tests/it/automation.rs::paragraph_grouping_survives_save_and_reopen_through_tools", "crates/edit/src/tests.rs::a_partial_rewrite_of_the_only_paragraph_stays_one_block", "crates/edit/src/tests.rs::a_partial_rewrite_closes_before_the_operator_that_follows_the_paragraph", "crates/edit/src/tests.rs::a_partial_rewrite_of_the_last_marked_paragraph_stays_inside_its_region", "crates/edit/src/tests.rs::a_partial_rewrite_keeps_the_next_marked_region_closed", "crates/edit/src/tests.rs::a_partial_rewrite_of_an_unmarked_paragraph_leaves_the_marked_neighbour_closed", "crates/edit/src/tests.rs::a_partial_rewrite_inside_one_marked_region_leaves_the_neighbour_inside_it", "crates/edit/src/tests.rs::a_partial_rewrite_inside_one_text_object_keeps_the_neighbour", "crates/edit/src/tests.rs::a_partial_rewrite_of_the_last_paragraph_in_one_text_object_keeps_the_one_before_it", "crates/automation/tests/it/automation.rs::a_partial_rewrite_of_the_last_paragraph_stays_one_through_tools", "crates/edit/src/tests.rs::text_lines_are_found_and_replaced_in_place", "crates/ui-egui/tests/it/editing.rs::editing_existing_text_in_place", "crates/automation/tests/it/automation.rs::editing_existing_text_through_tools"]
+notes = "lines grouped into paragraphs by stream, font, size, left alignment and regular baseline spacing; a blank line (about twice the paragraph's own leading) stays a separate paragraph, and editing the first one leaves the next in place (#2517). An explicit TL is that leading. Without one, Td does not set it: three or more rows at one repeated step stay one paragraph, and a single wider gap stays a break. A rewrite marks the whole paragraph, including a row it leaves in the source, so adding a row does not absorb the next paragraph on a later edit. When the paragraph is the last text on the page, that marker closes after the paragraph's last ET, so a kept source row stays inside it. When the next paragraph shares that text object, the marker opens after BT and closes before the neighbour's text. When the rewritten paragraph is the last one in that text object, the marker opens after the preceding paragraph and closes before the shared ET. The extra marker is not added when the paragraph is already one marked region and the next line is in a different region. Hyphenated line ends are joined. A row opening with a list marker starts its own item, and the row a list item wraps onto continues it at its hanging indent, so editing one item never takes the items after it. Still open: a larger heading joined to smaller body lines (#1756) and cells in different columns (#1680, #2478). Two rows and no third step still cannot be told from a paragraph break when there is no TL."
 
 [[feature]]
 id = "edit.font-reuse-substitution"