Fix caching of parsed border color values in CSS parser

When parsing CSS, a border-color value is parsed as four brushes, as css
allows assigning up to four values, one for each side.

When applying the CSS to the HTML, we accessed it as a color value,
which overwrote the parsed value with a QColor. So while we had a valid
parsed value (and didn't re-parse), the code accessing that value still
expected it to be a list, and thus failed to retrieve the data.

There are several ways to fix that, but the cleanest way without
introducing any performance penalty from repeatedly parsing (and in fact
removing a parse of the string into a color) is to enable colorValue to
interpret an already parsed value that is a list without overwriting the
parsed value again. To avoid similar issues in the future, add assert
that the parsed value has the right type in brushValues.

As a drive-by, speed things up further by making use of qMetaTypeId
being constexpr, which allows for it to be used in a switch statement.

Add a test case.

Fixes: QTBUG-96603
Pick-to: 6.2 5.15
Change-Id: Icdbff874daedc91bff497cd0cd1d99e4c713217c
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 11 insertions, 2 deletions

diff --git a/src/gui/text/qcssparser.cpp b/src/gui/text/qcssparser.cpp
index 574436d6f6..da3de4d651 100644
--- a/src/gui/text/qcssparser.cpp
+++ b/src/gui/text/qcssparser.cpp
@@ -1460,10 +1460,18 @@ QColor Declaration::colorValue(const QPalette &pal) const
         return QColor();
 
     if (d->parsed.isValid()) {
-        if (d->parsed.userType() == QMetaType::QColor)
+        switch (d->parsed.typeId()) {
+        case qMetaTypeId<QColor>():
             return qvariant_cast<QColor>(d->parsed);
-        if (d->parsed.userType() == QMetaType::Int)
+        case qMetaTypeId<int>():
             return pal.color((QPalette::ColorRole)(d->parsed.toInt()));
+        case qMetaTypeId<QList<QVariant>>():
+            if (d->parsed.toList().size() == 1) {
+                const auto &value = d->parsed.toList().at(0);
+                return qvariant_cast<QColor>(value);
+            }
+            break;
+        }
     }
 
     ColorData color = parseColorValue(d->values.at(0));
@@ -1507,6 +1515,7 @@ void Declaration::brushValues(QBrush *c, const QPalette &pal) const
     int i = 0;
     if (d->parsed.isValid()) {
         needParse = 0;
+        Q_ASSERT(d->parsed.metaType() == QMetaType::fromType<QList<QVariant>>());
         QList<QVariant> v = d->parsed.toList();
         for (i = 0; i < qMin(v.count(), 4); i++) {
             if (v.at(i).userType() == QMetaType::QBrush) {