QTextDocument: add css-styling of table cell borders to HTML import/export

Supported style attributes:

<table>
style: supports "border-collapse: collapse" and "border-color".
border: width of the outer border
bordercolor: basic color for all borders

<tr>
style: not supported

<td>/</th>
style: supports the "border", "border-[top|left|bottom|right]]"
       shorthand styles and the "border-width", "border-color"
       and "border-style" (and the top/left/bottom/right variants)
       attributes

<table border=1 style="border-collapse: collapse"> will render
a simple 1px table grid.

Notes:

The QTextDocument table model is much simpler than the HTML table model.
It basically only has <table> and <td> support. So the HTML parser is
forced to map markup and styling to the QTextDocument model which
is not without loss.

In other words: While QTextDocument -> HTML -> QTextDocument should
preserve the QTextDocument structure, HTML -> QTextDocument -> HTML
does not preserve the HTML DOM at all.

So for now the HTML importer and writer only support border styles on
the <td> and <th> nodes. In future updates, the HTML parser might be
enhanced to map <tr> and <table> CSS styles to the cells.

Change-Id: If9e7312fa6cbf270cf8f7b3c72ba1fa094107517
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 34 insertions, 0 deletions

diff --git a/src/gui/text/qtexthtmlparser.cpp b/src/gui/text/qtexthtmlparser.cpp
index 43b32e7e2c..5d37982a8b 100644
--- a/src/gui/text/qtexthtmlparser.cpp
+++ b/src/gui/text/qtexthtmlparser.cpp
@@ -491,12 +491,19 @@ QTextHtmlParserNode::QTextHtmlParserNode()
       listStyle(QTextListFormat::ListStyleUndefined), imageWidth(-1), imageHeight(-1), tableBorder(0),
       tableCellRowSpan(1), tableCellColSpan(1), tableCellSpacing(2), tableCellPadding(0),
       borderBrush(Qt::darkGray), borderStyle(QTextFrameFormat::BorderStyle_Outset),
+      borderCollapse(false),
       userState(-1), cssListIndent(0), wsm(WhiteSpaceModeUndefined)
 {
     margin[QTextHtmlParser::MarginLeft] = 0;
     margin[QTextHtmlParser::MarginRight] = 0;
     margin[QTextHtmlParser::MarginTop] = 0;
     margin[QTextHtmlParser::MarginBottom] = 0;
+
+    for (int i = 0; i < 4; ++i) {
+        tableCellBorderStyle[i] = QTextFrameFormat::BorderStyle_None;
+        tableCellBorder[i] = 0;
+        tableCellBorderBrush[i] = Qt::NoBrush;
+    }
 }
 
 void QTextHtmlParser::dumpHtml()
@@ -1169,6 +1176,25 @@ void QTextHtmlParserNode::applyCssDeclarations(const QVector<QCss::Declaration>
     QCss::ValueExtractor extractor(declarations);
     extractor.extractBox(margin, padding);
 
+    if (id == Html_td || id == Html_th) {
+        QCss::BorderStyle cssStyles[4];
+        int cssBorder[4];
+        QSize cssRadii[4]; // unused
+        for (int i = 0; i < 4; ++i) {
+            cssStyles[i] = QCss::BorderStyle_None;
+            cssBorder[i] = 0;
+        }
+        // this will parse (and cache) "border-width" as a list so the
+        // QCss::BorderWidth parsing below which expects a single value
+        // will not work as expected - which in this case does not matter
+        // because tableBorder is not relevant for cells.
+        extractor.extractBorder(cssBorder, tableCellBorderBrush, cssStyles, cssRadii);
+        for (int i = 0; i < 4; ++i) {
+            tableCellBorderStyle[i] = static_cast<QTextFrameFormat::BorderStyle>(cssStyles[i] - 1);
+            tableCellBorder[i] = static_cast<qreal>(cssBorder[i]);
+        }
+    }
+
     for (int i = 0; i < declarations.count(); ++i) {
         const QCss::Declaration &decl = declarations.at(i);
         if (decl.d->values.isEmpty()) continue;
@@ -1186,6 +1212,9 @@ void QTextHtmlParserNode::applyCssDeclarations(const QVector<QCss::Declaration>
         case QCss::BorderWidth:
             tableBorder = extractor.lengthValue(decl);
             break;
+        case QCss::BorderCollapse:
+            borderCollapse = decl.borderCollapseValue();
+            break;
         case QCss::Color: charFormat.setForeground(decl.colorValue()); break;
         case QCss::Float:
             cssFloat = QTextFrameFormat::InFlow;
@@ -1654,6 +1683,11 @@ void QTextHtmlParser::applyAttributes(const QStringList &attributes)
                     if (!c.isValid())
                         qWarning("QTextHtmlParser::applyAttributes: Unknown color name '%s'",value.toLatin1().constData());
                     node->charFormat.setBackground(c);
+                } else if (key == QLatin1String("bordercolor")) {
+                    QColor c; c.setNamedColor(value);
+                    if (!c.isValid())
+                        qWarning("QTextHtmlParser::applyAttributes: Unknown color name '%s'",value.toLatin1().constData());
+                    node->borderBrush = c;
                 } else if (key == QLatin1String("background")) {
                     node->applyBackgroundImage(value, resourceProvider);
                 } else if (key == QLatin1String("cellspacing")) {