QImageWriter: Do not assume that QIODevice::open() will succeed

For instance, if we are passed a QFile to a path that does not exist, being told
"No such file or directory" is significantly more useful than being told
"Device not writable".

Change-Id: I0cc72322f868f06ae2f77b3d0fac7e2094a1d2c7
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/gui/image/qimagewriter.cpp b/src/gui/image/qimagewriter.cpp
index fd2c51ebd8..ab15d8ee29 100644
--- a/src/gui/image/qimagewriter.cpp
+++ b/src/gui/image/qimagewriter.cpp
@@ -283,8 +283,13 @@ bool QImageWriterPrivate::canWriteHelper()
         errorString = QImageWriter::tr("Device is not set");
         return false;
     }
-    if (!device->isOpen())
-        device->open(QIODevice::WriteOnly);
+    if (!device->isOpen()) {
+        if (!device->open(QIODevice::WriteOnly)) {
+            imageWriterError = QImageWriter::DeviceError;
+            errorString = QImageWriter::tr("Cannot open device for writing: %1").arg(device->errorString());
+            return false;
+        }
+    }
     if (!device->isWritable()) {
         imageWriterError = QImageWriter::DeviceError;
         errorString = QImageWriter::tr("Device not writable");