Annotations outside of box are cut off when writing to file

[themikelau]

When annotations (created using the g5 option) are placed outside of the box by, e.g., suppling a negative starting x position, the dimensions of the exported image does not expand to include them. Currently, a workaround is to set the page margins manually using the SPLASH_MARGIN_XMIN environment variable or --xmin flag to use a suitable negative value.