Support CSS text-decoration-color in underlines, overlines, strikethrough

Also add a feature to the textedit example to set this value.

[ChangeLog][QtGui][CSS] The CSS text-decoration-color attribute is now
supported in rich text spans with underlines, overlines and strikethrough.

Fixes: QTBUG-82114
Task-number: QTBUG-39617
Change-Id: I0065cb5431833da55b0f503ce7ff2b83b74b718a
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

examples/widgets/richtext/textedit/textedit.cpp

@@ -354,6 +354,10 @@ void TextEdit::setupTextActions()
     actionTextColor = menu->addAction(pix, tr("&Color..."), this, &TextEdit::textColor);
     tb->addAction(actionTextColor);
 
+    const QIcon underlineColorIcon(rsrcPath + "/textundercolor.png");
+    actionUnderlineColor = menu->addAction(underlineColorIcon, tr("Underline color..."), this, &TextEdit::underlineColor);
+    tb->addAction(actionUnderlineColor);
+
     menu->addSeparator();
 
     const QIcon checkboxIcon = QIcon::fromTheme("status-checkbox-checked", QIcon(rsrcPath + "/checkbox-checked.png"));
@@ -729,6 +733,17 @@ void TextEdit::textColor()
     colorChanged(col);
 }
 
+void TextEdit::underlineColor()
+{
+    QColor col = QColorDialog::getColor(Qt::black, this);
+    if (!col.isValid())
+        return;
+    QTextCharFormat fmt;
+    fmt.setUnderlineColor(col);
+    mergeFormatOnWordOrSelection(fmt);
+    colorChanged(col);
+}
+
 void TextEdit::textAlign(QAction *a)
 {
     if (a == actionAlignLeft)

examples/widgets/richtext/textedit/textedit.h

@@ -95,6 +95,7 @@ private slots:
     void textSize(const QString &p);
     void textStyle(int styleIndex);
     void textColor();
+    void underlineColor();
     void textAlign(QAction *a);
     void setChecked(bool checked);
     void indent();
@@ -125,6 +126,7 @@ private:
     QAction *actionTextUnderline;
     QAction *actionTextItalic;
     QAction *actionTextColor;
+    QAction *actionUnderlineColor;
     QAction *actionAlignLeft;
     QAction *actionAlignCenter;
     QAction *actionAlignRight;

examples/widgets/richtext/textedit/textedit.qrc

@@ -22,6 +22,7 @@
   <file>images/mac/textleft.png</file>
   <file>images/mac/textright.png</file>
   <file>images/mac/textunder.png</file>
+  <file>images/mac/textundercolor.png</file>
   <file>images/mac/zoomin.png</file>
   <file>images/mac/zoomout.png</file>
   <file>images/win/checkbox.png</file>
@@ -45,6 +46,7 @@
   <file>images/win/textleft.png</file>
   <file>images/win/textright.png</file>
   <file>images/win/textunder.png</file>
+  <file>images/win/textundercolor.png</file>
   <file>images/win/zoomin.png</file>
   <file>images/win/zoomout.png</file>
   <file>example.html</file>

src/gui/painting/qpainter.cpp

@@ -6061,6 +6061,9 @@ static void drawTextItemDecoration(QPainter *painter, const QPointF &pos, const
     if (flags & QTextItem::StrikeOut) {
         QLineF strikeOutLine = line;
         strikeOutLine.translate(0., - fe->ascent().toReal() / 3.);
+        QColor uc = charFormat.underlineColor();
+        if (uc.isValid())
+            pen.setColor(uc);
         painter->setPen(pen);
         if (textEngine)
             textEngine->addStrikeOut(painter, strikeOutLine);
@@ -6071,6 +6074,9 @@ static void drawTextItemDecoration(QPainter *painter, const QPointF &pos, const
     if (flags & QTextItem::Overline) {
         QLineF overline = line;
         overline.translate(0., - fe->ascent().toReal());
+        QColor uc = charFormat.underlineColor();
+        if (uc.isValid())
+            pen.setColor(uc);
         painter->setPen(pen);
         if (textEngine)
             textEngine->addOverline(painter, overline);

src/gui/text/qcssparser.cpp

@@ -166,6 +166,7 @@ static const QCssKnownValue properties[NumProperties - 1] = {
     { "subcontrol-position", QtPosition },
     { "text-align", TextAlignment },
     { "text-decoration", TextDecoration },
+    { "text-decoration-color", TextDecorationColor },
     { "text-indent", TextIndent },
     { "text-transform", TextTransform },
     { "text-underline-style", TextUnderlineStyle },

src/gui/text/qcssparser_p.h

@@ -201,6 +201,7 @@ enum Property {
     QtIcon,
     LetterSpacing,
     WordSpacing,
+    TextDecorationColor,
     NumProperties
 };
 

src/gui/text/qtextdocument.cpp

@@ -2560,6 +2560,11 @@ bool QTextHtmlExporter::emitCharFormatStyle(const QTextCharFormat &format)
         if (!atLeastOneDecorationSet)
             html += QLatin1String("none");
         html += QLatin1Char(';');
+        if (format.hasProperty(QTextFormat::TextUnderlineColor)) {
+            html += QLatin1String(" text-decoration-color:");
+            html += colorValue(format.underlineColor());
+            html += QLatin1Char(';');
+        }
         attributesEmitted = true;
     } else {
         html.chop(decorationTag.size());

src/gui/text/qtextformat.cpp

@@ -642,7 +642,7 @@ Q_GUI_EXPORT QDataStream &operator>>(QDataStream &stream, QTextFormat &fmt)
     \omitvalue FirstFontProperty
     \omitvalue LastFontProperty
 
-    \value TextUnderlineColor
+    \value TextUnderlineColor      Specifies the color to draw underlines, overlines and strikeouts.
     \value TextVerticalAlignment
     \value TextOutline
     \value TextUnderlineStyle
@@ -1984,8 +1984,8 @@ QStringList QTextCharFormat::anchorNames() const
 /*!
     \fn void QTextCharFormat::setUnderlineColor(const QColor &color)
 
-    Sets the underline color used for the characters with this format to
+    Sets the color used to draw underlines, overlines and strikeouts on the
-    the \a color specified.
+    characters with this format to the \a color specified.
 
     \sa underlineColor()
 */
@@ -1993,7 +1993,8 @@ QStringList QTextCharFormat::anchorNames() const
 /*!
     \fn QColor QTextCharFormat::underlineColor() const
 
-    Returns the color used to underline the characters with this format.
+    Returns the color used to draw underlines, overlines and strikeouts
+    on the characters with this format.
 
     \sa setUnderlineColor()
 */

src/gui/text/qtexthtmlparser.cpp

@@ -1346,6 +1346,7 @@ void QTextHtmlParserNode::applyCssDeclarations(const QList<QCss::Declaration> &d
             default: break;
             }
             break;
+        case QCss::TextDecorationColor: charFormat.setUnderlineColor(decl.colorValue()); break;
         case QCss::ListStyleType:
         case QCss::ListStyle:
             setListStyle(decl.d->values);