fix: clear inherited ODF backgrounds and borders

CHANGELOG.md

@@ -16,6 +16,9 @@ The release run heads these entries with the version and opens a fresh
 
 ## Unreleased
 
+- Explicit transparent backgrounds and `none` borders override inherited ODF
+  styles, including after clearing a cell fill and reopening the document.
+
 - ODF charts reject unrepresentable geometry, bound axis/label conversions,
   and draw complete single-slice pies and rings without overflowing totals.
 

src/odr/internal/odf/odf_style.cpp

@@ -256,11 +256,27 @@ std::optional<Color> read_color(const pugi::xml_attribute attribute) {
   return {};
 }
 
-std::optional<std::string> read_border(const pugi::xml_attribute attribute) {
-  if (attribute && std::strcmp("none", attribute.value()) != 0) {
-    return attribute.value();
+/// A stated `transparent` clears the @p inherited background.
+std::optional<Color> read_background(const pugi::xml_attribute attribute,
+                                     const std::optional<Color> &inherited) {
+  if (std::strcmp("transparent", attribute.value()) == 0) {
+    return {};
   }
-  return {};
+  const std::optional<Color> color = read_color(attribute);
+  return color ? color : inherited;
+}
+
+/// A stated `none` clears the @p inherited border.
+std::optional<std::string>
+read_border(const pugi::xml_attribute attribute,
+            const std::optional<std::string> &inherited) {
+  if (!attribute) {
+    return inherited;
+  }
+  if (std::strcmp("none", attribute.value()) == 0) {
+    return {};
+  }
+  return attribute.value();
 }
 
 PageLayout read_page_layout(const pugi::xml_node node) {
@@ -396,10 +412,9 @@ void Style::resolve_text_style_(const StyleRegistry *registry,
           read_color(text_properties.attribute("fo:color"))) {
     result.font_color = font_color;
   }
-  if (const std::optional<Color> background_color =
-          read_color(text_properties.attribute("fo:background-color"))) {
-    result.background_color = background_color;
-  }
+  result.background_color =
+      read_background(text_properties.attribute("fo:background-color"),
+                      result.background_color);
   if (const pugi::xml_attribute text_position =
           text_properties.attribute("style:text-position")) {
     if (const std::optional<FontPosition> font_position =
@@ -528,10 +543,9 @@ void Style::resolve_table_cell_style_(const pugi::xml_node node,
           table_cell_properties.attribute("style:wrap-option")) {
     result.wrap_text = std::strcmp("wrap", wrap_option.value()) == 0;
   }
-  if (const std::optional<Color> background_color =
-          read_color(table_cell_properties.attribute("fo:background-color"))) {
-    result.background_color = background_color;
-  }
+  result.background_color =
+      read_background(table_cell_properties.attribute("fo:background-color"),
+                      result.background_color);
   if (const std::optional<Measure> padding =
           read_measure(table_cell_properties.attribute("fo:padding"))) {
     result.padding = DirectionalStyle(padding);
@@ -552,26 +566,19 @@ void Style::resolve_table_cell_style_(const pugi::xml_node node,
           read_measure(table_cell_properties.attribute("fo:padding-bottom"))) {
     result.padding.bottom = padding_bottom;
   }
-  if (const std::optional<std::string> border =
-          read_border(table_cell_properties.attribute("fo:border"))) {
-    result.border = DirectionalStyle(border);
-  }
-  if (const std::optional<std::string> border_right =
-          read_border(table_cell_properties.attribute("fo:border-right"))) {
-    result.border.right = border_right;
-  }
-  if (const std::optional<std::string> border_top =
-          read_border(table_cell_properties.attribute("fo:border-top"))) {
-    result.border.top = border_top;
-  }
-  if (const std::optional<std::string> border_left =
-          read_border(table_cell_properties.attribute("fo:border-left"))) {
-    result.border.left = border_left;
-  }
-  if (const std::optional<std::string> border_bottom =
-          read_border(table_cell_properties.attribute("fo:border-bottom"))) {
-    result.border.bottom = border_bottom;
-  }
+  if (const pugi::xml_attribute border =
+          table_cell_properties.attribute("fo:border")) {
+    result.border = DirectionalStyle(read_border(border, {}));
+  }
+  result.border.right = read_border(
+      table_cell_properties.attribute("fo:border-right"), result.border.right);
+  result.border.top = read_border(
+      table_cell_properties.attribute("fo:border-top"), result.border.top);
+  result.border.left = read_border(
+      table_cell_properties.attribute("fo:border-left"), result.border.left);
+  result.border.bottom =
+      read_border(table_cell_properties.attribute("fo:border-bottom"),
+                  result.border.bottom);
 }
 
 void Style::resolve_graphic_style_(const pugi::xml_node node,

test/src/internal/odf/odf_sheet_style_test.cpp

@@ -201,15 +201,42 @@ TEST(OdfSheetStyle, one_delta_on_one_base_is_one_style) {
 }
 
 TEST(OdfSheetStyle, a_fill_taken_away_is_written_transparent) {
-  const Document document =
-      document_of(flat_sheet(string_cell("a", "ce1"), red_cell_style));
-  const Sheet sheet = first_sheet(document);
-
-  sheet.set_cell_style(0, 0, fill(Color(0, 0, 0, 0)), {});
+  for (const bool named : {false, true}) {
+    const Document document = document_of(
+        flat_sheet(string_cell("a", "ce1"), named ? "" : red_cell_style,
+                   named ? red_cell_style : ""));
+    const Sheet sheet = first_sheet(document);
+    sheet.set_cell_style(0, 0, fill(Color(0, 0, 0, 0)), {});
+
+    EXPECT_EQ(fill_at(sheet, 0, 0), std::nullopt);
+    EXPECT_NE(saved(document).find(R"(fo:background-color="transparent")"),
+              std::string::npos);
+    EXPECT_EQ(fill_at(first_sheet(document_of(saved(document))), 0, 0),
+              std::nullopt);
+  }
+}
 
-  EXPECT_EQ(fill_at(sheet, 0, 0), std::nullopt);
-  EXPECT_NE(saved(document).find(R"(fo:background-color="transparent")"),
-            std::string::npos);
+TEST(OdfSheetStyle, explicit_transparency_and_no_border_override_inheritance) {
+  const Document document = document_of(flat_sheet(
+      string_cell("a", "child"),
+      R"(<style:style style:name="child" style:family="table-cell" )"
+      R"(style:parent-style-name="parent">)"
+      R"(<style:table-cell-properties fo:border="none" fo:border-left="1pt solid #000000" )"
+      R"(fo:background-color="transparent"/>)"
+      R"(<style:text-properties fo:background-color="transparent"/>)"
+      R"(</style:style>)",
+      R"(<style:style style:name="parent" style:family="table-cell">)"
+      R"(<style:table-cell-properties fo:background-color="#ff0000" fo:border="2pt solid #ff0000"/>)"
+      R"(<style:text-properties fo:background-color="#ff0000"/>)"
+      R"(</style:style>)"));
+  const Sheet sheet = first_sheet(document);
+  const TableCellStyle style = sheet.cell_style(0, 0);
+  EXPECT_EQ(style.background_color, std::nullopt);
+  EXPECT_EQ(style.border.top, std::nullopt);
+  EXPECT_EQ(style.border.right, std::nullopt);
+  EXPECT_EQ(style.border.bottom, std::nullopt);
+  EXPECT_EQ(style.border.left, "1pt solid #000000");
+  EXPECT_EQ(text_style_of(sheet, 0).background_color, std::nullopt);
 }
 
 TEST(OdfSheetStyle, an_alignment_is_fixed_on_the_cell) {