Add css media rule support for QTextDocument::setHtml()

CSS styles can contain '@media <rule> {...}' blocks, which were
previously ignored for all values except "screen".

To use a media rule other than the default "screen" rule,
specify it before calling setHtml() with setMetaInformation()
and the new info value 'CssMedia'.

[ChangeLog][Gui][QTextDocument] Add css media rule support
for QTextDocument::setHtml()

Pick-to: 6.3
Fixes: QTBUG-98408
Change-Id: Ie05f815a6dedbd970210f467e26b116f6ee3b9ca
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/gui/text/qtextdocument.cpp

@@ -351,6 +351,7 @@ QTextDocument *QTextDocument::clone(QObject *parent) const
     QTextDocumentPrivate *priv = doc->d_func();
     priv->title = d->title;
     priv->url = d->url;
+    priv->cssMedia = d->cssMedia;
     priv->pageSize = d->pageSize;
     priv->indentWidth = d->indentWidth;
     priv->defaultTextOption = d->defaultTextOption;
@@ -1135,6 +1136,8 @@ QString QTextDocument::metaInformation(MetaInformation info) const
         return d->title;
     case DocumentUrl:
         return d->url;
+    case CssMedia:
+        return d->cssMedia;
     }
     return QString();
 }
@@ -1155,6 +1158,9 @@ void QTextDocument::setMetaInformation(MetaInformation info, const QString &stri
     case DocumentUrl:
         d->url = string;
         break;
+    case CssMedia:
+        d->cssMedia = string;
+        break;
     }
 }
 
@@ -1242,11 +1248,14 @@ void QTextDocument::setPlainText(const QString &text)
     "<b>bold</b> text" will produce text where the first word has a font
     weight that gives it a bold appearance: "\b{bold} text".
 
+    To select a css media rule other than the default "screen" rule,
+    use setMetaInformation() with 'CssMedia' as "info" parameter.
+
     \note It is the responsibility of the caller to make sure that the
     text is correctly decoded when a QString containing HTML is created
     and passed to setHtml().
 
-    \sa setPlainText(), {Supported HTML Subset}
+    \sa setPlainText(), {Supported HTML Subset}, setMetaInformation()
 */
 
 #ifndef QT_NO_TEXTHTMLPARSER
@@ -1286,8 +1295,11 @@ void QTextDocument::setHtml(const QString &html)
     \value DocumentTitle    The title of the document.
     \value DocumentUrl      The url of the document. The loadResource() function uses
                             this url as the base when loading relative resources.
+    \value CssMedia         This value is used to select the corresponding '@media'
+                            rule, if any, from a specified CSS stylesheet when setHtml()
+                            is called. This enum value has been introduced in Qt 6.3.
 
-    \sa metaInformation(), setMetaInformation()
+    \sa metaInformation(), setMetaInformation(), setHtml()
 */
 
 static bool findInBlock(const QTextBlock &block, const QString &expression, int offset,

src/gui/text/qtextdocument.h

@@ -136,7 +136,8 @@ public:
 
     enum MetaInformation {
         DocumentTitle,
-        DocumentUrl
+        DocumentUrl,
+        CssMedia
     };
     void setMetaInformation(MetaInformation info, const QString &);
     QString metaInformation(MetaInformation info) const;

src/gui/text/qtextdocument_p.cpp

@@ -187,7 +187,8 @@ QTextDocumentPrivate::QTextDocumentPrivate()
     framesDirty(true),
     rtFrame(nullptr),
     initialBlockCharFormatIndex(-1), // set correctly later in init()
-    resourceProvider(nullptr)
+    resourceProvider(nullptr),
+    cssMedia(QStringLiteral("screen"))
 {
     editBlock = 0;
     editBlockCursorPosition = -1;

src/gui/text/qtextdocument_p.h

@@ -384,6 +384,7 @@ public:
     QSizeF pageSize;
     QString title;
     QString url;
+    QString cssMedia;
     qreal indentWidth;
     qreal documentMargin;
     QUrl baseUrl;

src/gui/text/qtexthtmlparser.cpp

@@ -2165,7 +2165,7 @@ QList<QCss::Declaration> QTextHtmlParser::declarationsForNode(int node) const
     for (int i = 0; i < inlineStyleSheets.count(); ++i, ++idx)
         selector.styleSheets[idx] = inlineStyleSheets.at(i);
 
-    selector.medium = QLatin1String("screen");
+    selector.medium = resourceProvider ? resourceProvider->metaInformation(QTextDocument::CssMedia) : QLatin1String("screen");
 
     QCss::StyleSelector::NodePtr n;
     n.id = node;

tests/auto/gui/text/qtextdocument/tst_qtextdocument.cpp

@@ -96,6 +96,7 @@ private slots:
     void toHtml2();
 
     void setFragmentMarkersInHtmlExport();
+    void setMediaRule();
 
     void toHtmlBodyBgColor();
     void toHtmlBodyBgColorRgba();
@@ -1910,6 +1911,39 @@ void tst_QTextDocument::setFragmentMarkersInHtmlExport()
     }
 }
 
+void tst_QTextDocument::setMediaRule()
+{
+    {
+        CREATE_DOC_AND_CURSOR();
+        doc.setDefaultStyleSheet("@media screen { p { background:#000000 } } @media print { p { background:#ffffff } }");
+        doc.setHtml("<p>Hello World</p>");
+
+        QString expected = htmlHead;
+        expected += QString("<p style=\" margin-top:12px; margin-bottom:12px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; background-color:#000000;\"><span style=\" background-color:#000000;\">Hello World</span></p>") + htmlTail;
+        QCOMPARE(doc.toHtml(), expected);
+    }
+    {
+        CREATE_DOC_AND_CURSOR();
+        doc.setDefaultStyleSheet("@media screen { p { background:#000000 } } @media print { p { background:#ffffff } }");
+        doc.setMetaInformation(QTextDocument::CssMedia, "screen");
+        doc.setHtml("<p>Hello World</p>");
+
+        QString expected = htmlHead;
+        expected += QString("<p style=\" margin-top:12px; margin-bottom:12px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; background-color:#000000;\"><span style=\" background-color:#000000;\">Hello World</span></p>") + htmlTail;
+        QCOMPARE(doc.toHtml(), expected);
+    }
+    {
+        CREATE_DOC_AND_CURSOR();
+        doc.setDefaultStyleSheet("@media screen { p { background:#000000 } } @media print { p { background:#ffffff } }");
+        doc.setMetaInformation(QTextDocument::CssMedia, "print");
+        doc.setHtml("<p>Hello World</p>");
+
+        QString expected = htmlHead;
+        expected += QString("<p style=\" margin-top:12px; margin-bottom:12px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; background-color:#ffffff;\"><span style=\" background-color:#ffffff;\">Hello World</span></p>") + htmlTail;
+        QCOMPARE(doc.toHtml(), expected);
+    }
+}
+
 void tst_QTextDocument::toHtmlBodyBgColor()
 {
     CREATE_DOC_AND_CURSOR();
@@ -2294,14 +2328,18 @@ void tst_QTextDocument::clonePreservesMetaInformation()
 {
     const QString title("Foobar");
     const QString url("about:blank");
+    const QString media("print");
     doc->setHtml("<html><head><title>" + title + "</title></head><body>Hrm</body></html>");
     doc->setMetaInformation(QTextDocument::DocumentUrl, url);
+    doc->setMetaInformation(QTextDocument::CssMedia, media);
     QCOMPARE(doc->metaInformation(QTextDocument::DocumentTitle), title);
     QCOMPARE(doc->metaInformation(QTextDocument::DocumentUrl), url);
+    QCOMPARE(doc->metaInformation(QTextDocument::CssMedia), media);
 
     QTextDocument *clone = doc->clone();
     QCOMPARE(clone->metaInformation(QTextDocument::DocumentTitle), title);
     QCOMPARE(clone->metaInformation(QTextDocument::DocumentUrl), url);
+    QCOMPARE(clone->metaInformation(QTextDocument::CssMedia), media);
     delete clone;
 }