QTextImageHandler: Resolve Nx images correctly for file or qrc URLs

The qt_findAtNxFile helper in qicon.cpp expects a local file name that
can be probed with QFile::exists. If the src attribute of an <img>
element specifies the location of the image as a file:/ or qrc:/ url
rather than as a local file name, then we need to strip the scheme
off the file path, and in the case of a qrc URL leave the :/ prefix
before calling the qt_findAtNxFile helper.

Amends, and partially reverts, 760df7256588e76d082ea959399af36d7ba80a86.
We can't avoid testing whether the source in the HTML is provided as a
URL before interpreting it as a file name.

Pick-to: 6.5 6.4 6.2
Fixes: QTBUG-109212
Change-Id: I7ea7a5bfde79bab90a8025c42e754129813dd0fc
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

2 files changed, 19 insertions, 12 deletions

diff --git a/src/gui/text/qtextimagehandler.cpp b/src/gui/text/qtextimagehandler.cpp
index b21ce6f2f9..3ce3a4bd54 100644
--- a/src/gui/text/qtextimagehandler.cpp
+++ b/src/gui/text/qtextimagehandler.cpp
@@ -17,20 +17,34 @@ QT_BEGIN_NAMESPACE
 
 using namespace Qt::StringLiterals;
 
-extern QString qt_findAtNxFile(const QString &baseFileName, qreal targetDevicePixelRatio,
-                               qreal *sourceDevicePixelRatio);
+static inline QString findAtNxFileOrResource(const QString &baseFileName,
+                                             qreal targetDevicePixelRatio,
+                                             qreal *sourceDevicePixelRatio)
+{
+    // qt_findAtNxFile expects a file name that can be tested with QFile::exists.
+    // so if the format.name() is a file:/ or qrc:/ URL, then we need to strip away the schema.
+    QString localFile = baseFileName;
+    if (localFile.startsWith("file:/"_L1))
+        localFile = localFile.sliced(6);
+    else if (localFile.startsWith("qrc:/"_L1))
+        localFile = localFile.sliced(3);
+
+    extern QString qt_findAtNxFile(const QString &baseFileName, qreal targetDevicePixelRatio,
+                                   qreal *sourceDevicePixelRatio);
+    return qt_findAtNxFile(localFile, targetDevicePixelRatio, sourceDevicePixelRatio);
+}
 
 static inline QUrl fromLocalfileOrResources(QString path)
 {
     if (path.startsWith(":/"_L1)) // auto-detect resources and convert them to url
-        path.prepend("qrc"_L1);
+        path = path.prepend("qrc"_L1);
     return QUrl(path);
 }
 
 static QPixmap getPixmap(QTextDocument *doc, const QTextImageFormat &format, const qreal devicePixelRatio = 1.0)
 {
     qreal sourcePixelRatio = 1.0;
-    const QString name = qt_findAtNxFile(format.name(), devicePixelRatio, &sourcePixelRatio);
+    const QString name = findAtNxFileOrResource(format.name(), devicePixelRatio, &sourcePixelRatio);
     const QUrl url = fromLocalfileOrResources(name);
 
     QPixmap pm;
@@ -100,7 +114,7 @@ static QSize getPixmapSize(QTextDocument *doc, const QTextImageFormat &format)
 static QImage getImage(QTextDocument *doc, const QTextImageFormat &format, const qreal devicePixelRatio = 1.0)
 {
     qreal sourcePixelRatio = 1.0;
-    const QString name = qt_findAtNxFile(format.name(), devicePixelRatio, &sourcePixelRatio);
+    const QString name = findAtNxFileOrResource(format.name(), devicePixelRatio, &sourcePixelRatio);
     const QUrl url = fromLocalfileOrResources(name);
 
     QImage image;
diff --git a/tests/auto/gui/text/qtextimagehandler/tst_qtextimagehandler.cpp b/tests/auto/gui/text/qtextimagehandler/tst_qtextimagehandler.cpp
index ca35cf0c75..b640efc8e4 100644
--- a/tests/auto/gui/text/qtextimagehandler/tst_qtextimagehandler.cpp
+++ b/tests/auto/gui/text/qtextimagehandler/tst_qtextimagehandler.cpp
@@ -71,13 +71,6 @@ void tst_QTextImageHandler::loadAtNImages()
         p.end();
         QVERIFY(!img.isNull());
         const auto expectedColor = dpr == 1 ? Qt::red : Qt::green;
-#ifdef Q_OS_ANDROID // On Android, file:/ fails completely
-        QEXPECT_FAIL("file_url", "file:/ schema not handled - QTBUG-109212", Continue);
-#else
-        if (dpr != 1)
-            QEXPECT_FAIL("file_url", "Nx images not resolved for file:/ schema - QTBUG-109212", Continue);
-#endif
-        QEXPECT_FAIL("qrc_url", "qrc:/ schema not handled - QTBUG-109212", Continue);
         QCOMPARE(img.pixelColor(0, 0), expectedColor);
     }
 }