Improve support for saving QImage to QSaveFile

When saving to a QIODevice, QImage and QImageWriter will automatically
deduct the file format from the filename if it determines that the
device is a QFile. That did not work for a QSaveFile device. Fix by
using the common ancestor, QFileDevice, in the implementation.

Fixes: QTBUG-89022
Pick-to: 6.2
Change-Id: Ie01d80df4f29ca0d4ff30bf7e1b77605293c070e
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 55 insertions, 0 deletions

diff --git a/tests/auto/gui/image/qimagewriter/tst_qimagewriter.cpp b/tests/auto/gui/image/qimagewriter/tst_qimagewriter.cpp
index 49a4504d2a..924174e358 100644
--- a/tests/auto/gui/image/qimagewriter/tst_qimagewriter.cpp
+++ b/tests/auto/gui/image/qimagewriter/tst_qimagewriter.cpp
@@ -36,6 +36,7 @@
 #include <QSet>
 #include <QTemporaryDir>
 #include <QTemporaryFile>
+#include <QSaveFile>
 
 #ifdef Q_OS_UNIX // for geteuid()
 # include <sys/types.h>
@@ -75,6 +76,7 @@ private slots:
     void saveWithNoFormat();
 
     void saveToTemporaryFile();
+    void saveToSaveFile();
 
     void writeEmpty();
 
@@ -530,6 +532,59 @@ void tst_QImageWriter::saveToTemporaryFile()
     }
 }
 
+void tst_QImageWriter::saveToSaveFile()
+{
+    QImage image(prefix + "kollada.png");
+    QVERIFY(!image.isNull());
+
+    {
+        // Check canWrite
+        QImageWriter writer;
+        QSaveFile file(writePrefix + "savefile0.png");
+        writer.setDevice(&file);
+        QVERIFY2(writer.canWrite(), qPrintable(writer.errorString()));
+    }
+
+    QString fileName1(writePrefix + "savefile1.garble");
+    {
+        // Check failing canWrite
+        QVERIFY(!QFileInfo(fileName1).exists());
+        QImageWriter writer;
+        QSaveFile file(fileName1);
+        writer.setDevice(&file);
+        QVERIFY(!writer.canWrite());
+        QCOMPARE(writer.error(), QImageWriter::UnsupportedFormatError);
+    }
+    QVERIFY(!QFileInfo(fileName1).exists());
+
+    QString fileName2(writePrefix + "savefile2.png");
+    {
+        QImageWriter writer;
+        QSaveFile file(fileName2);
+        writer.setDevice(&file);
+        QCOMPARE(writer.fileName(), fileName2);
+        QVERIFY2(writer.write(image), qPrintable(writer.errorString()));
+        QVERIFY(file.commit());
+    }
+    {
+        QImage tmp;
+        QVERIFY(tmp.load(fileName2, "PNG"));
+        QCOMPARE(tmp, image);
+    }
+
+    QString fileName3(writePrefix + "savefile3.png");
+    {
+        QSaveFile file(fileName3);
+        QVERIFY(image.save(&file));
+        QVERIFY(file.commit());
+    }
+    {
+        QImage tmp;
+        QVERIFY(tmp.load(fileName3, "PNG"));
+        QCOMPARE(tmp, image);
+    }
+}
+
 void tst_QImageWriter::writeEmpty()
 {
     // check writing a null QImage errors gracefully