QTextDocument: Add support for responsive images

Add support for the max-width css attribute in image. This allows images
to be responsive: it adapts their size to the size of the QTextDocument
so that they never grow bigger than the QTextDocument pageSize.

This is implemented for the image handler used in QTextEdit and other
QtWidget text related classes.

[ChangeLog][QtGui][CSS] The max-width style can now be applied to
<img/> to set the maximum width in pixels or percentage.

Task-number: QTBUG-12283
Change-Id: Ic94e16279a1240ab4a509823de59dc0bfc920bb9
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 65 insertions, 1 deletions

diff --git a/tests/auto/gui/text/qtextimagehandler/tst_qtextimagehandler.cpp b/tests/auto/gui/text/qtextimagehandler/tst_qtextimagehandler.cpp
index 8327a5d187..0048623d0e 100644
--- a/tests/auto/gui/text/qtextimagehandler/tst_qtextimagehandler.cpp
+++ b/tests/auto/gui/text/qtextimagehandler/tst_qtextimagehandler.cpp
@@ -6,6 +6,10 @@
 #include <QPainter>
 #include <private/qtextimagehandler_p.h>
 
+using namespace Qt::StringLiterals;
+
+// #define DEBUG_WRITE_HTML
+
 class tst_QTextImageHandler : public QObject
 {
     Q_OBJECT
@@ -20,6 +24,8 @@ private slots:
     void loadAtNImages_data();
 #ifndef QT_NO_TEXTHTMLPARSER
     void loadAtNImages();
+    void maxWidth_data();
+    void maxWidth();
 #endif
 };
 
@@ -61,7 +67,7 @@ void tst_QTextImageHandler::loadAtNImages()
     const auto it = std::find_if(formats.begin(), formats.end(), [](const auto &format){
         return format.objectType() == QTextFormat::ImageObject;
     });
-    QVERIFY(it != formats.end());
+    QCOMPARE_NE(it, formats.end());
     const QTextImageFormat format = (*it).toImageFormat();
     QTextImageHandler handler;
 
@@ -77,6 +83,64 @@ void tst_QTextImageHandler::loadAtNImages()
         QCOMPARE(img.pixelColor(0, 0), expectedColor);
     }
 }
+
+void tst_QTextImageHandler::maxWidth_data()
+{
+    QTest::addColumn<QString>("imageFile");
+    QTest::addColumn<QSizeF>("pageSize");
+    QTest::addColumn<QTextLength>("maxWidth");
+    QTest::addColumn<QSizeF>("expectedSize");
+
+    QTest::addRow("constrained-percentage") << QFINDTESTDATA("data/image.png") << QSizeF(16, 16) << QTextLength(QTextLength::PercentageLength, 100) << QSizeF(12, 12);
+    QTest::addRow("not-constrained-percentage") << QFINDTESTDATA("data/image.png") << QSizeF(200, 200) << QTextLength(QTextLength::PercentageLength, 100) << QSizeF(16, 16);
+    QTest::addRow("constrained-fixed") << QFINDTESTDATA("data/image.png") << QSizeF(16, 16) << QTextLength(QTextLength::FixedLength, 5) << QSizeF(5, 5);
+    QTest::addRow("not-constrained-fixed") << QFINDTESTDATA("data/image.png") << QSizeF(200, 200) << QTextLength(QTextLength::FixedLength, 5) << QSizeF(5, 5);
+    QTest::addRow("not-constrained-default") << QFINDTESTDATA("data/image.png") << QSizeF(200, 200) << QTextLength(QTextLength::VariableLength, 5) << QSizeF(16, 16);
+}
+
+void tst_QTextImageHandler::maxWidth()
+{
+    QFETCH(QString, imageFile);
+    QFETCH(QSizeF, pageSize);
+    QFETCH(QTextLength, maxWidth);
+    QFETCH(QSizeF, expectedSize);
+
+    QTextDocument doc;
+    doc.setPageSize(pageSize);
+    doc.setDocumentMargin(2);
+    QTextCursor c(&doc);
+    QString style;
+    if (maxWidth.type() == QTextLength::PercentageLength)
+        style = " style=\"max-width:"_L1 + QString::number(maxWidth.rawValue()) + "%;\""_L1;
+    else if (maxWidth.type() == QTextLength::FixedLength)
+        style = " style=\"max-width:"_L1 + QString::number(maxWidth.rawValue()) + "px;\""_L1;
+    const QString html = "<img src=\"" + imageFile + u'\"' + style + "\">";
+    c.insertHtml(html);
+
+#ifdef DEBUG_WRITE_HTML
+    {
+        QFile out("/tmp/" + QLatin1String(QTest::currentDataTag()) + ".html");
+        out.open(QFile::WriteOnly);
+        out.write(html.toLatin1());
+        out.close();
+    }
+    {
+        QFile out("/tmp/" + QLatin1String(QTest::currentDataTag()) + "_rewrite.html");
+        out.open(QFile::WriteOnly);
+        out.write(doc.toHtml().toLatin1());
+        out.close();
+    }
+#endif
+    const auto formats = doc.allFormats();
+    const auto it = std::find_if(formats.begin(), formats.end(), [](const auto &format){
+        return format.objectType() == QTextFormat::ImageObject;
+    });
+    QCOMPARE_NE(it, formats.end());
+    const QTextImageFormat format = (*it).toImageFormat();
+    QTextImageHandler handler;
+
+    QCOMPARE(handler.intrinsicSize(&doc, 0, format), expectedSize);
+}
 #endif
 
 QTEST_MAIN(tst_QTextImageHandler)