QGIS » QGIS Application

Case:
A WMS from QGIS Server is displayed wrong - data is not stretched correctly.

Problem:
I have a qgis-project which contains layers published as a WMS with QGIS Server (ubuntu). The bbox has the width/height ration 758/682 = 1.111. But when I make a WMS-requst where the bbox is changed, the data is not stretch correctly - e.g. the bbox is changed to 1046/706=1.482 and the data is displayed wrong.

This is in violation to the WMS-specification(http://www.opengeospatial.org/standards/wms):
"If the request is for a picture format, the returned picture, regardless of its MIME type, shall have exactly the
specified width and height in pixels. In the case where the aspect ratio of the BBOX and the ratio width/height are
different, the WMS shall stretch the returned map so that the resulting pixels could themselves be rendered in the
aspect ratio of the BBOX. In other words, it shall be possible using this definition to request a map for a device
whose output pixels are themselves non-square, or to stretch a map into an image area of a different aspect ratio."