Comment 5 for bug 669267

from 'src/extension/internal/cairo-png-out.cpp':
 * A quick hack to use the Cairo renderer to write out a file. This
 * then makes 'save as...' PNG.

Related issue:
The internal output extension 'org.inkscape.output.png.cairo' seems to get used (instead of 'sp_export_png_file()'?) when pasting the clipboard contents from Inkscape into e.g. a raster image editor like GIMP: the pasted images always have a white solid background and show the same rendering errors (e.g. with patterns) or missing filter effects as when saving an SVG drawing as "Cairo PNG".

Bug #404826 “copy an object from inkscape to system clipboard doesn't keep transparency”