Just in case the chat website will be down at some point, here is Bryce's reply:
hi Moini
it does look like Cairo will emit an error if the image size is out of bounds, so the lack of an error message may be on the Inkscape side.
it creates an error surface, so inkscape would need to check for that and display an error dialog
bryce 7:34 PM
the reason for the limitation is due to a design limit in Pixman, which has a fixed maximum image size. Looking into the pixman code, there are some hard assumptions in there about the data types which would be extremely non-trivial to change.
(I'm looking at pixman-bits-image.c and create_bits() in particular)
one observation though is that the above is true only for the *image* backend in Cairo. Other backends (like xcb which we use for display on Linux, or win32 on windows) may have different size capabilities, but I'm not certain.
anyway, as to the question of changing cairo's max size, it'd require some programming effort to rework the code to use larger data types in Pixman, and/or to (maybe) use a different Cairo backend in Inkscape when generating PNG's.
a workaround may be to do the export in four separate PNGs via the Inkscape command line, and then combine them as a post-processing step.
So this means:
- it cannot be changed easily
- one would need to do a lot of difficult work in the pixman library to change this
- there is a way to work around this, by exporting smaller areas via command line, then stitching them together
- Inkscape should at least issue an error message (or maybe it could also implement the workaround).
