From 296e67254ed94b1dcf47e5669fff925cb0dc1e71 Mon Sep 17 00:00:00 2001
From: Mirco Miranda <mircomir@gmail.com>
Date: Thu, 1 May 2025 10:45:04 +0200
Subject: [PATCH] Fix wrong device position after read options

---
 src/imageformats/jxr.cpp | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/imageformats/jxr.cpp b/src/imageformats/jxr.cpp
index 7124f53..b671685 100644
--- a/src/imageformats/jxr.cpp
+++ b/src/imageformats/jxr.cpp
@@ -243,6 +243,22 @@ public:
         return true;
     }
 
+    /*!
+     * \brief initForReadingAndRollBack
+     * Initialize the device for reading and rollback the device to start position.
+     * \param device The source device.
+     * \return True on success, otherwise false.
+     */
+    bool initForReadingAndRollBack(QIODevice *device)
+    {
+        if (device)
+            device->startTransaction();
+        auto ok = initForReading(device);
+        if (device)
+            device->rollbackTransaction();
+        return ok;
+    }
+
     /*!
      * \brief jxrFormat
      * \return The JXR format.
@@ -1153,7 +1169,7 @@ QVariant JXRHandler::option(ImageOption option) const
     QVariant v;
 
     if (option == QImageIOHandler::Size) {
-        if (d->initForReading(device())) {
+        if (d->initForReadingAndRollBack(device())) {
             auto size = d->imageSize();
             if (size.isValid()) {
                 v = QVariant::fromValue(size);
@@ -1162,7 +1178,7 @@ QVariant JXRHandler::option(ImageOption option) const
     }
 
     if (option == QImageIOHandler::ImageFormat) {
-        if (d->initForReading(device())) {
+        if (d->initForReadingAndRollBack(device())) {
             v = QVariant::fromValue(d->imageFormat());
         }
     }
@@ -1173,7 +1189,7 @@ QVariant JXRHandler::option(ImageOption option) const
 
     if (option == QImageIOHandler::ImageTransformation) {
         // ignore result: I might want to read the value set in writing
-        d->initForReading(device());
+        d->initForReadingAndRollBack(device());
         v = int(d->transformation());
     }