[css-images] Clarification about Nx as <resolution> value in image-set() is needed #461
Description
Current syntax for image-set() is:
image-set() = image-set( <image-set-option># )
<image-set-option> = [ <image> | <string> ] <resolution>
Where <resolution> refers to CSS Values and Units Module Level 3 where it described as dimension with dpi, dpcm or dppx unit. However in example below we can see (that even works in some browsers):
background-image: image-set( "foo.png" 1x,
"foo-2x.png" 2x,
"foo-print.png" 600dpi );
I can't find reference where it says that dimension with x unit can be used as <resolution>. Looks like this is image-set() specific or I'm wrong. In any case, clarification is needed here.