postscript: Reordering of images to prolog increases memory requirement for printing
I noticed commit 9d372ca9 has changed the way images are written out, before they were defined in-place, now they are all defined in the prolog. When using old printers with little memory, it can take a lot of time for them to receive the data and the memory space for temporary storage of all the images can be exhausted quickly. Before the commit the printer could start right away and would only pause when receiving a page with a huge image, after the usage of the image, the memory of it can be discarded and re-used. (Disclaimer: I have not looked into the actual cairo source to verify this scenario.) We have not run into this problem yet fortunately but our printers are old and if something can go wrong, it usually will.