fix(html): give a paragraph its own font, and an empty one a line break

CHANGELOG.md

@@ -16,6 +16,13 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- A paragraph states its own font, so a run that names none of its own is read
+  at that font instead of at nothing. Slides whose text was there but invisible
+  now show it.
+- An empty paragraph keeps the height its font implies, whether or not the file
+  names a size for it, and copying across one yields a blank line.
+- A sheet's cells read in the font the file names, falling back to the sheet's
+  own only where it names none.
 - An image stays inside its frame on a page read without the shipped stylesheet,
   rather than covering the whole page.
 - A frame that names a side instead of an offset sits on that side, so a centred

src/odr/internal/html/document_element.cpp

@@ -300,6 +300,36 @@ void html::translate_line_break(const Element &element,
   state.out().write_element_end("x-s");
 }
 
+namespace {
+
+/// Whether a reader sees anything. A bookmark marks a place rather than filling
+/// one, and a span or a link is a style around what it holds, so a paragraph
+/// holding only those is still an empty line.
+bool has_content(const ElementRange &children) {
+  for (const Element child : children) {
+    switch (child.type()) {
+    case ElementType::bookmark:
+      break;
+    case ElementType::span:
+    case ElementType::link:
+      if (has_content(child.children())) {
+        return true;
+      }
+      break;
+    case ElementType::text:
+      if (!child.as_text().content().empty()) {
+        return true;
+      }
+      break;
+    default:
+      return true;
+    }
+  }
+  return false;
+}
+
+} // namespace
+
 void html::translate_paragraph(const Element &element,
                                const WritingState &state,
                                const std::string &marker) {
@@ -308,34 +338,29 @@ void html::translate_paragraph(const Element &element,
   state.out().write_element_begin(
       "x-p",
       HtmlElementOptions().set_inline(true).set_style(
-          "display:block;" + translate_paragraph_style(paragraph.style())));
+          "display:block;" + translate_paragraph_style(paragraph.style()) +
+          translate_block_font_style(paragraph.text_style())));
   if (!marker.empty()) {
     state.out().write_element_begin(
         "x-s", HtmlElementOptions()
                    .set_inline(true)
                    .set_class("odr-list-marker")
                    .set_style(translate_text_style(paragraph.text_style())));
-    // The tab separates label from text once copied; `x-p` collapses to
-    // `font-size:0`, so the marker has to carry the item's text style itself.
+    // The tab separates label from text once copied.
     state.out().out() << escape_text(marker) << "&#9;";
     state.out().write_element_end("x-s");
   }
   translate_children(paragraph.children(), state);
-  if (paragraph.first_child()) {
-    // TODO if element is content (e.g. bookmark does not count)
-
-    // TODO example `encrypted-exception-3$aabbcc$.odt` at the very bottom
-    // TODO has a missing line break after "As the result of the project we ..."
-
-    // TODO example `style-missing+image-1.odt` first paragraph has no height
+  if (marker.empty() && !has_content(paragraph.children())) {
+    // A line break, not a break opportunity: only a break is copied, so a blank
+    // line between two paragraphs survives being pasted somewhere else.
+    state.out().write_element_begin(
+        "br", HtmlElementOptions().set_close_type(HtmlCloseType::none));
   } else {
+    // A paragraph whose content is all out of flow has no line box of its own.
     state.out().write_element_begin(
-        "x-s", HtmlElementOptions().set_inline(true).set_style(
-                   translate_text_style(paragraph.text_style())));
-    state.out().write_element_end("x-s");
+        "wbr", HtmlElementOptions().set_close_type(HtmlCloseType::none));
   }
-  state.out().write_element_begin(
-      "wbr", HtmlElementOptions().set_close_type(HtmlCloseType::none));
   state.out().write_element_end("x-p");
 }
 

src/odr/internal/html/document_style.cpp

@@ -194,6 +194,21 @@ std::string html::translate_text_style(const TextStyle &text_style) {
   return result;
 }
 
+std::string html::translate_block_font_style(const TextStyle &text_style) {
+  std::string result;
+  if (const std::optional<std::string_view> font_name = text_style.font_name;
+      font_name.has_value()) {
+    result.append("font-family:")
+        .append(escape_attribute(std::string(*font_name)))
+        .append(";");
+  }
+  if (const std::optional<Measure> font_size = text_style.font_size;
+      font_size.has_value()) {
+    result.append("font-size:").append(font_size->to_string()).append(";");
+  }
+  return result;
+}
+
 std::string
 html::translate_paragraph_style(const ParagraphStyle &paragraph_style) {
   std::string result;

src/odr/internal/html/document_style.hpp

@@ -38,6 +38,8 @@ std::string translate_outer_page_style(const PageLayout &page_layout);
 std::string translate_outer_flowing_page_style(const PageLayout &page_layout);
 std::string translate_inner_page_style(const PageLayout &page_layout);
 std::string translate_text_style(const TextStyle &text_style);
+/// The part of a text style a block may carry: what paints belongs on the run.
+std::string translate_block_font_style(const TextStyle &text_style);
 std::string translate_paragraph_style(const ParagraphStyle &paragraph_style);
 std::string translate_table_style(const TableStyle &table_style);
 std::string

src/odr/internal/html/frontend.cpp

@@ -23,7 +23,7 @@ body{margin:0;background:#fff}
 /* What the formats anchor against: a page for shapes, a paragraph or a cell
    for frames. */
 x-p,td,.odr-page-outer{position:relative}
-x-p{display:block;font-size:0}
+x-p{display:block}
 x-s{display:inline}
 .odr-background{padding:0;background:#525659}
 /* The page column, sized to the widest page so pages of differing width centre
@@ -61,9 +61,9 @@ body{margin:0;background:var(--odr-sheet-canvas)}
 /* The sheet's own cells, not a table the document itself drew inside one. */
 .odr-sheet>tbody>tr>td{vertical-align:bottom;height:inherit;padding:1px 6px}
 .odr-sheet>tbody>tr>td>x-p{height:inherit}
-/* Sheet-wide, not cell-only: a shape's text would otherwise fall to the
-   `font-size:0` a page carries. */
-.odr-sheet x-p{font-family:var(--odr-sheet-font);font-size:10pt}
+/* The font anything in a cell falls back to, a shape's text included, where the
+   file names none of its own. */
+.odr-sheet>tbody>tr>td x-p{font-family:var(--odr-sheet-font);font-size:10pt}
 /* Sticky cells in a collapsed border model do not repaint their borders in
    Chrome or WebKit, so the ruler uses inset shadows. */
 .odr-sheet th{position:sticky;background:var(--odr-sheet-ruler);color:var(--odr-sheet-ruler-text);font:500 12px/1.6 var(--odr-sheet-font);text-align:center;vertical-align:middle;padding:0 4px;white-space:nowrap;user-select:none}

test/data.cmake

@@ -17,9 +17,9 @@ odr_test_data(
 odr_test_data(
         PATH "reference-output/odr-public"
         URL "https://github.com/opendocument-app/OpenDocument.test.output.git"
-        REVISION "26c71049d2cbdc32ca3ea982fb814bddbc90c5fe")
+        REVISION "1964c34c2a6bd84d8178d9586ba59a04f172b7f2")
 
 odr_test_data(
         PATH "reference-output/odr-private"
         URL "https://github.com/opendocument-app/OpenDocument.test-private.output.git"
-        REVISION "372fb6ed9733047835ff17d6056518e6482eea3c")
+        REVISION "5e5f035f8a6e6c86ad5d978887607e8b9167c019")

test/src/internal/html/document_style_test.cpp

@@ -35,3 +35,24 @@ TEST(html_document_style, outer_flowing_page_style_without_height) {
   EXPECT_EQ(ihtml::translate_outer_flowing_page_style(page_layout),
             "width:21cm;");
 }
+
+TEST(html_document_style, block_font_style_carries_the_font) {
+  TextStyle text_style;
+  text_style.font_name = "Arial";
+  text_style.font_size = Measure("14pt");
+  EXPECT_EQ(ihtml::translate_block_font_style(text_style),
+            "font-family:Arial;font-size:14pt;");
+}
+
+TEST(html_document_style, block_font_style_leaves_what_paints_to_the_run) {
+  TextStyle text_style;
+  text_style.font_size = Measure("14pt");
+  text_style.font_weight = FontWeight::bold;
+  text_style.background_color = Color(0xff, 0xff, 0x00);
+  text_style.font_underline = true;
+  EXPECT_EQ(ihtml::translate_block_font_style(text_style), "font-size:14pt;");
+}
+
+TEST(html_document_style, block_font_style_of_a_style_naming_no_font) {
+  EXPECT_EQ(ihtml::translate_block_font_style(TextStyle()), "");
+}