Generalize image file name @2x suffix handling to higher scale factors

@3x is in use on iOS already, so extend the handling in QImageReader
to all single-digit factors, like QIcon does.

Fixes: QTBUG-76273
Change-Id: Ic9442731c0549dbe8f797e1ddb1a09d8447e8441
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
 

5 files changed, 31 insertions, 4 deletions

diff --git a/src/gui/image/qimagereader.cpp b/src/gui/image/qimagereader.cpp
index 0fb1d808e5..0c75196612 100644
--- a/src/gui/image/qimagereader.cpp
+++ b/src/gui/image/qimagereader.cpp
@@ -1319,10 +1319,12 @@ bool QImageReader::read(QImage *image)
         }
     }
 
-    // successful read; check for "@2x" file name suffix and set device pixel ratio.
-    static bool disable2xImageLoading = !qEnvironmentVariableIsEmpty("QT_HIGHDPI_DISABLE_2X_IMAGE_LOADING");
-    if (!disable2xImageLoading && QFileInfo(fileName()).baseName().endsWith(QLatin1String("@2x"))) {
-           image->setDevicePixelRatio(2.0);
+    // successful read; check for "@Nx" file name suffix and set device pixel ratio.
+    static bool disableNxImageLoading = !qEnvironmentVariableIsEmpty("QT_HIGHDPI_DISABLE_2X_IMAGE_LOADING");
+    if (!disableNxImageLoading) {
+        const QByteArray suffix = QFileInfo(fileName()).baseName().right(3).toLatin1();
+        if (suffix.length() == 3 && suffix[0] == '@' && suffix[1] >= '2' && suffix[1] <= '9' && suffix[2] == 'x')
+            image->setDevicePixelRatio(suffix[1] - '0');
     }
     if (autoTransform())
         qt_imageTransform(*image, transformation());
diff --git a/tests/auto/gui/image/qimagereader/images/qticon16.png b/tests/auto/gui/image/qimagereader/images/qticon16.png
new file mode 100644
index 0000000000..b6b01a4d64
--- /dev/null
+++ b/tests/auto/gui/image/qimagereader/images/qticon16.png
diff --git a/tests/auto/gui/image/qimagereader/images/qticon16@2x.png b/tests/auto/gui/image/qimagereader/images/qticon16@2x.png
new file mode 100644
index 0000000000..205461daf0
--- /dev/null
+++ b/tests/auto/gui/image/qimagereader/images/qticon16@2x.png
diff --git a/tests/auto/gui/image/qimagereader/images/qticon16@3x.png b/tests/auto/gui/image/qimagereader/images/qticon16@3x.png
new file mode 100644
index 0000000000..de92658241
--- /dev/null
+++ b/tests/auto/gui/image/qimagereader/images/qticon16@3x.png
diff --git a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
index c2ec5b8925..1eee2f273e 100644
--- a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
+++ b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
@@ -164,6 +164,9 @@ private slots:
     void preserveTexts_data();
     void preserveTexts();
 
+    void devicePixelRatio_data();
+    void devicePixelRatio();
+
 private:
     QString prefix;
     QTemporaryDir m_temporaryDir;
@@ -1976,6 +1979,28 @@ void tst_QImageReader::preserveTexts()
     QCOMPARE(r.text(key3), text3.simplified());
 }
 
+void tst_QImageReader::devicePixelRatio_data()
+{
+    QTest::addColumn<QString>("fileName");
+    QTest::addColumn<QSize>("size");
+    QTest::addColumn<qreal>("dpr");
+
+    QTest::newRow("1x") << "qticon16.png" << QSize(16, 16) << 1.0;
+    QTest::newRow("2x") << "qticon16@2x.png" << QSize(32, 32) << 2.0;
+    QTest::newRow("3x") << "qticon16@3x.png" << QSize(48, 48) << 3.0;
+}
+
+void tst_QImageReader::devicePixelRatio()
+{
+    QFETCH(QString, fileName);
+    QFETCH(QSize, size);
+    QFETCH(qreal, dpr);
+
+    QImageReader r(":/images/" + fileName);
+    QImage img = r.read();
+    QCOMPARE(img.size(), size);
+    QCOMPARE(img.devicePixelRatio(), dpr);
+}
 
 QTEST_MAIN(tst_QImageReader)
 #include "tst_qimagereader.moc"