Support foreground gradient in CSS parser and HTML generator

Qt supports some complex foreground brushes which we cannot
express using normal CSS, so we introduce a Qt-specific property
for this. We already had some support for background gradients
in widget style sheets, but this expands support to foreground
brushes of text when converting a QTextDocument from and to HTML.

It also adds an optional "coordinatemode" attribute to the
gradient functions so that this can be faithfully restored from HTML.

Task-number: QTBUG-123357
Change-Id: I3d6dd828f68272995c8525bec5a7b421fdbed670
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

4 files changed, 66 insertions, 6 deletions

diff --git a/src/gui/text/qcssparser.cpp b/src/gui/text/qcssparser.cpp
index 5861003de6..ac6ddc69a8 100644
--- a/src/gui/text/qcssparser.cpp
+++ b/src/gui/text/qcssparser.cpp
@@ -39,6 +39,7 @@ static const QCssKnownValue properties[NumProperties - 1] = {
     { "-qt-background-role", QtBackgroundRole },
     { "-qt-block-indent", QtBlockIndent },
     { "-qt-fg-texture-cachekey", QtForegroundTextureCacheKey },
+    { "-qt-foreground", QtForeground },
     { "-qt-line-height-type", QtLineHeightType },
     { "-qt-list-indent", QtListIndent },
     { "-qt-list-number-prefix", QtListNumberPrefix },
@@ -814,6 +815,10 @@ static BrushData parseBrushValue(const QCss::Value &v, const QPalette &pal)
     QStringList spreads;
     spreads << "pad"_L1 << "reflect"_L1 << "repeat"_L1;
 
+    int coordinateMode = -1;
+    QStringList coordinateModes;
+    coordinateModes << "logical"_L1 << "stretchtodevice"_L1 << "objectbounding"_L1 << "object"_L1;
+
     bool dependsOnThePalette = false;
     Parser parser(lst.at(1));
     while (parser.hasNext()) {
@@ -840,11 +845,12 @@ static BrushData parseBrushValue(const QCss::Value &v, const QPalette &pal)
             parser.next();
             QCss::Value value;
             (void)parser.parseTerm(&value);
-            if (attr.compare("spread"_L1, Qt::CaseInsensitive) == 0) {
+            if (attr.compare("spread"_L1, Qt::CaseInsensitive) == 0)
                 spread = spreads.indexOf(value.variant.toString());
-            } else {
+            else if (attr.compare("coordinatemode"_L1, Qt::CaseInsensitive) == 0)
+                coordinateMode = coordinateModes.indexOf(value.variant.toString());
+            else
                 vars[attr] = value.variant.toReal();
-            }
         }
         parser.skipSpace();
         (void)parser.test(COMMA);
@@ -853,7 +859,7 @@ static BrushData parseBrushValue(const QCss::Value &v, const QPalette &pal)
     if (gradType == 0) {
         QLinearGradient lg(vars.value("x1"_L1), vars.value("y1"_L1),
                            vars.value("x2"_L1), vars.value("y2"_L1));
-        lg.setCoordinateMode(QGradient::ObjectBoundingMode);
+        lg.setCoordinateMode(coordinateMode < 0 ? QGradient::ObjectBoundingMode : QGradient::CoordinateMode(coordinateMode));
         lg.setStops(stops);
         if (spread != -1)
             lg.setSpread(QGradient::Spread(spread));
@@ -867,7 +873,7 @@ static BrushData parseBrushValue(const QCss::Value &v, const QPalette &pal)
         QRadialGradient rg(vars.value("cx"_L1), vars.value("cy"_L1),
                            vars.value("radius"_L1), vars.value("fx"_L1),
                            vars.value("fy"_L1));
-        rg.setCoordinateMode(QGradient::ObjectBoundingMode);
+        rg.setCoordinateMode(coordinateMode < 0 ? QGradient::ObjectBoundingMode : QGradient::CoordinateMode(coordinateMode));
         rg.setStops(stops);
         if (spread != -1)
             rg.setSpread(QGradient::Spread(spread));
@@ -879,7 +885,7 @@ static BrushData parseBrushValue(const QCss::Value &v, const QPalette &pal)
 
     if (gradType == 2) {
         QConicalGradient cg(vars.value("cx"_L1), vars.value("cy"_L1), vars.value("angle"_L1));
-        cg.setCoordinateMode(QGradient::ObjectBoundingMode);
+        cg.setCoordinateMode(coordinateMode < 0 ? QGradient::ObjectBoundingMode : QGradient::CoordinateMode(coordinateMode));
         cg.setStops(stops);
         if (spread != -1)
             cg.setSpread(QGradient::Spread(spread));
diff --git a/src/gui/text/qcssparser_p.h b/src/gui/text/qcssparser_p.h
index a2d3622c7d..c1cfb1ac9b 100644
--- a/src/gui/text/qcssparser_p.h
+++ b/src/gui/text/qcssparser_p.h
@@ -169,6 +169,7 @@ enum Property {
     QtAccent,
     QtStrokeWidth,
     QtStrokeColor,
+    QtForeground,
     NumProperties
 };
 
diff --git a/src/gui/text/qtextdocument.cpp b/src/gui/text/qtextdocument.cpp
index dc94643e8a..15a313e13d 100644
--- a/src/gui/text/qtextdocument.cpp
+++ b/src/gui/text/qtextdocument.cpp
@@ -2646,6 +2646,53 @@ bool QTextHtmlExporter::emitCharFormatStyle(const QTextCharFormat &format)
             html += " -qt-fg-texture-cachekey:"_L1;
             html += QString::number(cacheKey);
             html += ";"_L1;
+        } else if (brush.style() == Qt::LinearGradientPattern
+                   || brush.style() == Qt::RadialGradientPattern
+                   || brush.style() == Qt::ConicalGradientPattern) {
+            const QGradient *gradient = brush.gradient();
+            if (gradient->type() == QGradient::LinearGradient) {
+                const QLinearGradient *linearGradient = static_cast<const QLinearGradient *>(brush.gradient());
+
+                html += " -qt-foreground: qlineargradient("_L1;
+                html += "x1:"_L1 + QString::number(linearGradient->start().x()) + u',';
+                html += "y1:"_L1 + QString::number(linearGradient->start().y()) + u',';
+                html += "x2:"_L1 + QString::number(linearGradient->finalStop().x()) + u',';
+                html += "y2:"_L1 + QString::number(linearGradient->finalStop().y()) + u',';
+            } else if (gradient->type() == QGradient::RadialGradient) {
+                const QRadialGradient *radialGradient = static_cast<const QRadialGradient *>(brush.gradient());
+
+                html += " -qt-foreground: qradialgradient("_L1;
+                html += "cx:"_L1 + QString::number(radialGradient->center().x()) + u',';
+                html += "cy:"_L1 + QString::number(radialGradient->center().y()) + u',';
+                html += "fx:"_L1 + QString::number(radialGradient->focalPoint().x()) + u',';
+                html += "fy:"_L1 + QString::number(radialGradient->focalPoint().y()) + u',';
+                html += "radius:"_L1 + QString::number(radialGradient->radius()) + u',';
+            } else {
+                const QConicalGradient *conicalGradient = static_cast<const QConicalGradient *>(brush.gradient());
+
+                html += " -qt-foreground: qconicalgradient("_L1;
+                html += "cx:"_L1 + QString::number(conicalGradient->center().x()) + u',';
+                html += "cy:"_L1 + QString::number(conicalGradient->center().y()) + u',';
+                html += "angle:"_L1 + QString::number(conicalGradient->angle()) + u',';
+            }
+
+            const QStringList coordinateModes = { "logical"_L1, "stretchtodevice"_L1, "objectbounding"_L1, "object"_L1 };
+            html += "coordinatemode:"_L1;
+            html += coordinateModes.at(int(gradient->coordinateMode()));
+            html += u',';
+
+            const QStringList spreads = { "pad"_L1, "reflect"_L1, "repeat"_L1 };
+            html += "spread:"_L1;
+            html += spreads.at(int(gradient->spread()));
+
+            for (const QGradientStop &stop : gradient->stops()) {
+                html += ",stop:"_L1;
+                html += QString::number(stop.first);
+                html += u' ';
+                html += colorValue(stop.second);
+            }
+
+            html += ");"_L1;
         } else {
             html += " color:"_L1;
             html += colorValue(brush.color());
diff --git a/src/gui/text/qtexthtmlparser.cpp b/src/gui/text/qtexthtmlparser.cpp
index df6e678827..05b9a1385f 100644
--- a/src/gui/text/qtexthtmlparser.cpp
+++ b/src/gui/text/qtexthtmlparser.cpp
@@ -1405,6 +1405,12 @@ void QTextHtmlParserNode::applyCssDeclarations(const QList<QCss::Declaration> &d
             }
             break;
         }
+        case QCss::QtForeground:
+        {
+            QBrush brush = decl.brushValue();
+            charFormat.setForeground(brush);
+            break;
+        }
         default: break;
         }
     }