[chaley]

Followup: thinking about the 'cover' issue, I realized that I can add new code to calibre to indicate presence or absence of a cover, with no performance impact. What I cannot do is provide the path to the cover file.

I added a new template function, has_cover() that returns 'Yes' if the book has a cover, otherwise '', making it ideal for a 'test' condition. I have submitted the code for inclusion in the next release (0.8.9). Once that function is available, then the coloring code will look like

program:
first_non_empty(
	cmp(field('rating'), 5, '', 'silver', ''),
	test(field('formats'), '', 'red'),
	test(field('comments'), '', 'fuchsia'),
	test(has_cover(), '', 'fuchsia'),
	'black'
)

Also, should someone want to make a yes/no column that indicates whether or not a book has a cover, create a column made from other columns (a composite column), check the 'use checkmarks' box, then enter the following as the template.

program: ifempty(has_cover(), 'No')