Use QColor(0, 0, 0, 0) to mark body text in QStaticText

QStaticTextPrivate::paintText() now uses QColor(0, 0, 0, 0) to mark
body text. QPainter's pen color was used before this commit
(that was always black) that leads to different colors of body text if,
for example, links are in body (first block painted with correct color
set by QPainter::setPen() but after link body text was always black).
Now QPainter::drawStaticText() will draw body text with set pen in
any case.

[ChangeLog][QtGui][Important Behavior Changes] Fixed a bug where
QStaticText would not use the QPainter's pen color for text when other
text colors were also in use. Internally this reserves
QColor(0, 0, 0, 0) for use with QStaticText.

Task-number: QTBUG-45957
Change-Id: If3e180e3083cdac1b4236e738acd15572f19ab69
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

src/gui/painting/qpainter.cpp

@@ -5744,7 +5744,7 @@ void QPainter::drawStaticText(const QPointF &topLeftPosition, const QStaticText
     if (d->extended == 0
             || !d->state->matrix.isAffine()
             || !fe->supportsTransformation(d->state->matrix)) {
-        staticText_d->paintText(topLeftPosition, this);
+        staticText_d->paintText(topLeftPosition, this, pen().color());
         return;
     }
 
@@ -5816,11 +5816,16 @@ void QPainter::drawStaticText(const QPointF &topLeftPosition, const QStaticText
 
     QPen oldPen = d->state->pen;
     QColor currentColor = oldPen.color();
+    static const QColor bodyIndicator(0, 0, 0, 0);
     for (int i=0; i<staticText_d->itemCount; ++i) {
         QStaticTextItem *item = staticText_d->items + i;
-        if (item->color.isValid() && currentColor != item->color) {
+        if (item->color.isValid() && currentColor != item->color
+            && item->color != bodyIndicator) {
                 setPen(item->color);
                 currentColor = item->color;
+        } else if (item->color == bodyIndicator) {
+            setPen(oldPen);
+            currentColor = oldPen.color();
         }
         d->extended->drawStaticTextItem(item);
 

src/gui/text/qstatictext.cpp

@@ -435,7 +435,7 @@ namespace {
     public:
         DrawTextItemRecorder(bool untransformedCoordinates, bool useBackendOptimizations)
                 : m_dirtyPen(false), m_useBackendOptimizations(useBackendOptimizations),
-                  m_untransformedCoordinates(untransformedCoordinates), m_currentColor(Qt::black)
+                  m_untransformedCoordinates(untransformedCoordinates), m_currentColor(0, 0, 0, 0)
         {
         }
 
@@ -599,7 +599,7 @@ namespace {
     };
 }
 
-void QStaticTextPrivate::paintText(const QPointF &topLeftPosition, QPainter *p)
+void QStaticTextPrivate::paintText(const QPointF &topLeftPosition, QPainter *p, const QColor &pen)
 {
     bool preferRichText = textFormat == Qt::RichText
                           || (textFormat == Qt::AutoText && Qt::mightBeRichText(text));
@@ -631,15 +631,16 @@ void QStaticTextPrivate::paintText(const QPointF &topLeftPosition, QPainter *p)
         textLayout.endLayout();
 
         actualSize = textLayout.boundingRect().size();
+        p->setPen(pen);
         textLayout.draw(p, topLeftPosition);
     } else {
         QTextDocument document;
 #ifndef QT_NO_CSSPARSER
-        QColor color = p->pen().color();
+        document.setDefaultStyleSheet(QString::fromLatin1("body { color: rgba(%1, %2, %3, %4%) }")
-        document.setDefaultStyleSheet(QString::fromLatin1("body { color: #%1%2%3 }")
+                                      .arg(QString::number(pen.red()))
-                                      .arg(QString::number(color.red(), 16), 2, QLatin1Char('0'))
+                                      .arg(QString::number(pen.green()))
-                                      .arg(QString::number(color.green(), 16), 2, QLatin1Char('0'))
+                                      .arg(QString::number(pen.blue()))
-                                      .arg(QString::number(color.blue(), 16), 2, QLatin1Char('0')));
+                                      .arg(QString::number(pen.alpha())));
 #endif
         document.setDefaultFont(font);
         document.setDocumentMargin(0.0);
@@ -657,7 +658,7 @@ void QStaticTextPrivate::paintText(const QPointF &topLeftPosition, QPainter *p)
         p->save();
         p->translate(topLeftPosition);
         QAbstractTextDocumentLayout::PaintContext ctx;
-        ctx.palette.setColor(QPalette::Text, p->pen().color());
+        ctx.palette.setColor(QPalette::Text, pen);
         document.documentLayout()->draw(p, ctx);
         p->restore();
 
@@ -682,7 +683,7 @@ void QStaticTextPrivate::init()
         painter.setFont(font);
         painter.setTransform(matrix);
 
-        paintText(QPointF(0, 0), &painter);
+        paintText(QPointF(0, 0), &painter, QColor(0, 0, 0, 0));
     }
 
     QVector<QStaticTextItem> deviceItems = device.items();

src/gui/text/qstatictext_p.h

@@ -131,7 +131,7 @@ public:
     ~QStaticTextPrivate();
 
     void init();
-    void paintText(const QPointF &pos, QPainter *p);
+    void paintText(const QPointF &pos, QPainter *p, const QColor &pen);
 
     void invalidate()
     {