Rewind the input stream after failing to load image from it.

For seekable streams, don't change the current position when loading image
fails. This allows the subsequent image handlers to succeed during image
format auto-detection even if a previous, erroneously chosen, handler failed.

Closes #12702.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66252 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/src/common/image.cpp b/src/common/image.cpp
index f17d1cbf2511f2d136cfd4bdaa6baf05fb864052..89f35d5d5743ba4a0360fb514f6ea69f1a134aed 100644 (file)
--- a/src/common/image.cpp
+++ b/src/common/image.cpp
@@ -2376,8 +2376,20 @@ bool wxImage::DoLoad(wxImageHandler& handler, wxInputStream& stream, int index)
     const unsigned maxWidth = GetOptionInt(wxIMAGE_OPTION_MAX_WIDTH),
                    maxHeight = GetOptionInt(wxIMAGE_OPTION_MAX_HEIGHT);
 
+    // Preserve the original stream position if possible to rewind back to it
+    // if we failed to load the file -- maybe the next handler that we try can
+    // succeed after us then.
+    wxFileOffset posOld = wxInvalidOffset;
+    if ( stream.IsSeekable() )
+        posOld = stream.TellI();
+
     if ( !handler.LoadFile(this, stream, true/*verbose*/, index) )
+    {
+        if ( posOld != wxInvalidOffset )
+            stream.SeekI(posOld);
+
         return false;
+    }
 
     // rescale the image to the specified size if needed
     if ( maxWidth || maxHeight )