QImageReader::read(): fetch filename once

The code in the Q_TRACE_ENABLED case was doing the same sort of
qobject_cast that is done in the fileName() accessor; so it's both a
code deduplication and an optimization to get the filename into a
local variable once, and use it both for tracing and for the
@Nx suffix check below.

Task-number: QTBUG-100578
Change-Id: Id7bde4ddbab38e20694c09cc7b412fec091672de
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 3 insertions, 5 deletions

diff --git a/src/gui/image/qimagereader.cpp b/src/gui/image/qimagereader.cpp
index fe0c01e54c..83d3784005 100644
--- a/src/gui/image/qimagereader.cpp
+++ b/src/gui/image/qimagereader.cpp
@@ -1246,11 +1246,9 @@ bool QImageReader::read(QImage *image)
         d->handler->setOption(QImageIOHandler::Quality, d->quality);
 
     // read the image
+    QString filename = fileName();
     if (Q_TRACE_ENABLED(QImageReader_read_before_reading)) {
-        QString fileName = QStringLiteral("unknown");
-        if (QFile *file = qobject_cast<QFile *>(d->device))
-            fileName = file->fileName();
-        Q_TRACE(QImageReader_read_before_reading, this, fileName);
+        Q_TRACE(QImageReader_read_before_reading, this, filename.isEmpty() ? u"unknown"_qs : filename);
     }
 
     const bool result = d->handler->read(image);
@@ -1317,7 +1315,7 @@ bool QImageReader::read(QImage *image)
     // 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();
+        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');
     }