fix(docx): keep the space above a paragraph or spacer the layout moves to a new page

CHANGELOG.md

@@ -8,6 +8,16 @@ follow semantic versioning; release dates are ISO 8601.
 
 ### Public API
 
+- **A body paragraph or spacer the layout moves to a new page keeps the space above it there
+  in DOCX.** The page starts a paragraph a page break moves down at its own top edge, with the
+  containers opening there, and keeps the gap before it too where the gap did not fit at the
+  foot of the page above. Word drops a paragraph's space above at the top of a page:
+  `ModernProfessional`'s second page opens with a heading its section pads 8pt down, and in
+  Word it stood 7.7pt high with everything under it; `Executive`'s opens with the spacer
+  between two entries 3pt down, and stood 3.2pt high. That space is now a line's height, which
+  Word keeps, the gap that stays at the foot of the page above left as the space above that
+  line, so Word breaks the page where it did. Lines more than 2pt off fall from 15 to none for
+  `Executive` and from 5 to none for `ModernProfessional`, in both editors.
 - **What follows a line holding only a drawn shape stands where the page sets it in DOCX.**
   A shape is written as a picture a transparent frame larger than its ink on every side, and
   Word makes a line of pictures and no text, grown to them, as tall as the pictures, frame

docs/recipes/docx-export.md

@@ -67,16 +67,16 @@ creation date is real metadata.
 
 | Document node | DOCX output |
 |---|---|
-| Paragraphs | Word paragraphs with alignment, font, size, colour, bold/italic/underline; inline runs preserved; a `\n` in the text is a line break (`w:br`), which Word would otherwise read as a space; a table cell's `text("a\nb")` stays one line, as the page sets it; a `bulletOffset` of spaces is an indent — the wrapped lines (`FROM_SECOND_LINE`), the first (`FIRST_LINE`) or all of them start that far in, measured in the paragraph's style as the page measures it; a prefix with letters in it is not written, but the wrapped lines still start after the spaces the page covers it with; no prefix is applied to a paragraph written over the flow, as one of an overlay's left-and-right pair, or in a header or footer |
+| Paragraphs | Word paragraphs with alignment, font, size, colour, bold/italic/underline; inline runs preserved; a `\n` in the text is a line break (`w:br`), which Word would otherwise read as a space; a table cell's `text("a\nb")` stays one line, as the page sets it; a `bulletOffset` of spaces is an indent — the wrapped lines (`FROM_SECOND_LINE`), the first (`FIRST_LINE`) or all of them start that far in, measured in the paragraph's style as the page measures it; a prefix with letters in it is not written, but the wrapped lines still start after the spaces the page covers it with; no prefix is applied to a paragraph written over the flow, as one of an overlay's left-and-right pair, or in a header or footer. A body paragraph the layout moves to a new page keeps the space the layout leaves above its text there — its own top edge, the edges of the containers opening with it, and the gap before it where the gap did not fit at the foot of the page above — as an empty line that tall before it, kept with it, since Word drops a paragraph's space above at the top of a page and keeps a line's height; the rest of the space owed stays above that line, so Word breaks the page where it did, and the gap between the paragraph's lines comes off the line as it would off its space above. A paragraph in a table cell, an overlay or a list is left to its container |
 | Lists | Real Word lists: a `numbering.xml` definition per list, `w:numPr` on each item, and the authored marker as the level's text. Nesting is a list level, so Enter continues the list and Tab demotes an item. See "What a list becomes" below for the kinds that stay plain paragraphs |
-| Tables | Word tables, one cell per cell. Each cell states its own padding, on all four sides, so a row is as tall as the page draws it: as `w:tcMar`, and above and below partly in its paragraphs. Word and LibreOffice give every cell of a row the largest top and bottom margin of any cell in it, so a row's cells are written with its smallest, and the rest of a cell's padding above and below is space above its first paragraph and below its last (measured: a row whose day cells were padded 5.5pt above and 10.25pt below beside a label padded 0.75pt stood 60.3pt tall in both editors, where its tallest cell came to 46). A cell opening with a table has no paragraph above it to hold its padding, and a cell in a vertical merge has its bottom edge in another row: these keep their margins, and the row's comes down no lower than the largest of them. Its padding above and below gives up the room Word makes for the table's horizontal rules — half of a rule between two rows to each, the lower row's rule where the two differ, the rule above the table and the one below it whole to their row — which the page does not (measured: a 0.75pt rule made each row 0.75pt taller). A cell that holds nothing but an empty line — a row that is only a rule, its thickness the empty cell's font — has that line cut to the room its row leaves it, the page's row less the cell's own margins and border: the page draws the rule's borders across the line, and Word and LibreOffice keep them outside it and grow the row (measured: `CobaltRota`'s two rules under a 0.9pt border stood 0.9pt taller each). A line with letters, a picture or a paragraph border of its own keeps its height. A table that states no rule is written with the engine's default 1pt black rule, as the page draws it, not left on Word's thinner grid. Its `textAnchor` becomes `w:vAlign` and the paragraph's `w:jc`, with the engine's default — the vertical middle, on the left — where Word's is the top, so a line beside a taller neighbour sits where the page puts it and an amount column stays right-aligned. A cell with no style of its own is set in the engine's default cell face rather than the document's Normal. A cell's lines are one paragraph with line breaks; when its style's `lineSpacing(...)` is above zero and it has more than one line, they are a paragraph each, with the spacing after every line but the last, since Word has no space between the lines of one paragraph but a taller line. A column sized to its content gets a point more than the page gives it, so the editor's font substitute cannot wrap its widest cell. The width is written when the document states one or every column is fixed; otherwise Word sizes the table — see "What falls back". A table breaks across pages where the layout breaks it: every row the layout placed is kept whole (`w:cantSplit`), `repeatHeader(n)` rows repeat on each page (`w:tblHeader`) and stay with the row under them. Two tables in a row — rows included, since a row is carried as a table — are kept apart by a paragraph a tenth of a point tall, holding the rest of the gap between them: an editor joins two tables with nothing between them into one. A table or a row the layout moves to a new page keeps its own top edge there, as the page does — written as a line that tall, kept with it, since Word drops a paragraph's space above at the top of a page — while the gap between it and the block before stays at the foot of the page above, where it fits there; a paragraph moved to a new page does not yet keep its own |
+| Tables | Word tables, one cell per cell. Each cell states its own padding, on all four sides, so a row is as tall as the page draws it: as `w:tcMar`, and above and below partly in its paragraphs. Word and LibreOffice give every cell of a row the largest top and bottom margin of any cell in it, so a row's cells are written with its smallest, and the rest of a cell's padding above and below is space above its first paragraph and below its last (measured: a row whose day cells were padded 5.5pt above and 10.25pt below beside a label padded 0.75pt stood 60.3pt tall in both editors, where its tallest cell came to 46). A cell opening with a table has no paragraph above it to hold its padding, and a cell in a vertical merge has its bottom edge in another row: these keep their margins, and the row's comes down no lower than the largest of them. Its padding above and below gives up the room Word makes for the table's horizontal rules — half of a rule between two rows to each, the lower row's rule where the two differ, the rule above the table and the one below it whole to their row — which the page does not (measured: a 0.75pt rule made each row 0.75pt taller). A cell that holds nothing but an empty line — a row that is only a rule, its thickness the empty cell's font — has that line cut to the room its row leaves it, the page's row less the cell's own margins and border: the page draws the rule's borders across the line, and Word and LibreOffice keep them outside it and grow the row (measured: `CobaltRota`'s two rules under a 0.9pt border stood 0.9pt taller each). A line with letters, a picture or a paragraph border of its own keeps its height. A table that states no rule is written with the engine's default 1pt black rule, as the page draws it, not left on Word's thinner grid. Its `textAnchor` becomes `w:vAlign` and the paragraph's `w:jc`, with the engine's default — the vertical middle, on the left — where Word's is the top, so a line beside a taller neighbour sits where the page puts it and an amount column stays right-aligned. A cell with no style of its own is set in the engine's default cell face rather than the document's Normal. A cell's lines are one paragraph with line breaks; when its style's `lineSpacing(...)` is above zero and it has more than one line, they are a paragraph each, with the spacing after every line but the last, since Word has no space between the lines of one paragraph but a taller line. A column sized to its content gets a point more than the page gives it, so the editor's font substitute cannot wrap its widest cell. The width is written when the document states one or every column is fixed; otherwise Word sizes the table — see "What falls back". A table breaks across pages where the layout breaks it: every row the layout placed is kept whole (`w:cantSplit`), `repeatHeader(n)` rows repeat on each page (`w:tblHeader`) and stay with the row under them. Two tables in a row — rows included, since a row is carried as a table — are kept apart by a paragraph a tenth of a point tall, holding the rest of the gap between them: an editor joins two tables with nothing between them into one. A table or a row the layout moves to a new page keeps its own top edge there, as the page does — written as a line that tall, kept with it, since Word drops a paragraph's space above at the top of a page — while the gap between it and the block before stays at the foot of the page above, where it fits there; a gap the layout carries onto the new page, because it did not fit at the foot of the page above, is not yet held above a table (body paragraphs and spacers: see their rows) |
 | Composed cells (`DocumentTableCell.node(...)`) | Written by the same writers that write that node anywhere else, so a cell built from an image, a list or a table carries it. A nested table is a real `w:tbl` followed by the paragraph Word requires a cell to end with — a hairline, which the paragraph written next in the cell takes over, so no empty line opens under the table, and whose mark is hidden where it is left at the cell's end holding nothing and no space, since LibreOffice lays it out — and takes the width of the column it sits in — the column's, not the one the page gives it, because the layout reports a composed cell's content under the owner's path |
 | Inline chips (`inlineCode(...)`, `inlineChip(...)`, `highlight(...)`) | The chip's fill becomes the run's own `w:shd`, in a paragraph and in a list item alike. Its shape does not travel — see "What a chip keeps and loses" below |
 | Images | Embedded pictures at the node's declared size |
 | Links and anchors | A `linkTarget` becomes a `w:hyperlink` — a relationship for an address, `w:anchor` for one of the document's own anchors — and a run's own link wins over the paragraph's — in a list item as much as in a paragraph. An `anchor(...)` becomes a bookmark wrapping that paragraph's text, named as Word requires; on a section, container, table or image it wraps everything the block wrote, from the start of its first paragraph to the end of its last, so a link to a block lands on its first line. A `bookmark(...)` outline level becomes Word's own `HeadingN` style, which is what puts the paragraph in the Navigation Pane, the outline view and a generated table of contents. The style states the outline level and nothing else, so the paragraph keeps its own formatting. The role comes from what the document declared, never from how big the text is |
 | Rows | A one-row table spanning the content width — or only its columns, where fixed columns leave part of the row empty — so editors keep the side-by-side layout. The row's slots become the column grid when they are weights, an even split or fixed columns; fixed columns that add up to less than the row leave the rest of it empty, the last one at its own width and the table no wider than its columns, so its text wraps where the page wraps it; the gap and the row's padding ride in the neighbouring column and come back out as that cell's margin; a cell holds whatever its child is, written as it is anywhere else. The row's `verticalAlign` is every cell's `w:vAlign`, so a child shorter than the row sits at its middle or bottom as on the page — a table of contents' leader on its entry's baseline. The row is kept whole across a page break, as the layout keeps it. A row is held at least as tall as the page makes it inside a painted panel, and anywhere its tallest child is a drawing Word holds nothing of in its cell — a badge beside a heading. A section or other container in any cell — a row's, a table's, a panel's — that pulls its first line up with a negative top edge writes that one-line paragraph as much shorter, its text seated where the page sets it — no more than the room above its letters, as Word draws an exact line's text only inside the line |
 | Sections / containers | Children written in order. A timeline with its markers on the rail (`markerOnRail()`) lays each entry's body out in the header row's content column, below the row; the body is written in the flow, indented to that column where the page puts it. A container with a fill, per-side borders or a uniform stroke is a one-cell table carrying them, its padding as the cell's margins, so a card keeps its panel — see "What a panel keeps and loses" below. A `keepTogether()` or `keepWithNext()` block the layout placed on one page stays on one page in Word too (`w:keepLines` + `w:keepNext`, and a row that may not split for a panel) |
-| Spacers | An empty paragraph a tenth of a point tall; the spacer's height is the space above the next block, or below this paragraph when a table follows |
+| Spacers | An empty paragraph a tenth of a point tall; the spacer's height is the space above the next block, or below this paragraph when a table follows. A spacer in the body the layout moves to a new page with the gap before it, because the gap did not fit at the foot of the page above, holds the space the layout leaves above it there — that gap, and the edges of any containers opening with it — in its line, which Word keeps at the top of a page where it drops the space above |
 | Page breaks | Explicit Word page breaks |
 
 Page geometry (size, margins and orientation — a page wider than it is tall is stated as