Comment 8 for bug 43730

That last one is invalid. I was incorrectly assuming that a non-false return from sp_export_png_file meant that a file was exported. I've now changed sp_export_png_file's return type to "int", and all existing code works as before, but sp_export_png_file returns 1 on success, and -1 on abort, instead of true on both.

This patch now states "Export aborted." instead of incorrectly reporting "Drawing exported to..", even though it's aborted. Hopefully that should do it, sorry about that last one!