Add support for the !important attribute

[LaurenzV]

This solves the problem I had where I wanted to achieve that I can override all styles in the SVG via stylesheet injection. I tested it with rsvg-convert and it works in the same way, so it would be great to have this merged. :)

[RazrFalcon]

Are you sure !important shouldn't be handled on the simplecss side? I genuinely have no idea how it suppose to work.

[LaurenzV]

Are you sure !important shouldn't be handled on the simplecss side? I genuinely have no idea how it suppose to work.

I think simplecss is low-level enough that it's enough if it provides the information whether an attribute has the important value or not, which is what it currently does. And since style deduplication is handled on the resvg side right now, we have to do it there anyway.

[RazrFalcon]

Looks good to me.

[RazrFalcon]

#252

[LaurenzV]

Will try it.

[LaurenzV]

Seems to work as intended. :)

Before:

After:

[LaurenzV]

I just noticed this, though:

When a declaration is important, the order of precedence is reversed. Declarations marked as important in the user-agent style sheets override all important declarations in the user style sheets. Similarly, all important declarations in the user style sheets override all important declarations in the author's style sheets. Finally, all important declarations take precedence over all animations.

So I think I need to adapt the swapping condition a bit. Will do so a bit later.

[LaurenzV]

The condition should probably be:

• Existing is not important, new is not important -> swap
• Existing is important, new is not important -> don't swap
• Existing is not important, new is important -> swap
• Existing is important, new is important -> don't swap (since the order is reversed, so existing important attributes take precedence over new important attributes)

Will adapt it and extend the test cases.

[LaurenzV]

Should be good now.

[LaurenzV]

Is this okay to merge? Not sure who to ping, @waywardmonkeys maybe?

[waywardmonkeys]

@LaurenzV Well, I think @RazrFalcon said it looks good, so I think I can approve it and you can merge it?

[DJMcNab]

It's Linebender policy to not merge without an approval. #843 (comment) is close enough to approval that I'm happy to formalise it, although I'll just give the actual change a quick scan.

[DJMcNab]

Thanks!

[LaurenzV]

Thanks!

[DJMcNab]

where I wanted to achieve that I can override all styles in the SVG via stylesheet injection

Incidentally, does the new swapping behaviour not break this? This injection is basically equivalent to a user agent/user stylesheet, right?

[LaurenzV]

Incidentally, does the new swapping behaviour not break this? This injection is basically equivalent to a user agent/user stylesheet, right?

Hmm, do you have an example? I don't think so though, otherwise the test cases wouldn't work. :D The swapping behavior also existed before, all I changed is that in case the original attribute in the injected stylesheet had !important, it will not be swapped (and thus not removed from the style chain).

[DJMcNab]

Ooh, I see. That makes so much more sense.
I had the condition inverted in my head.

Because my intuition was that the user stylesheet would override the document, since that seems obviously correct. But that's not how the spec is written (the document overwriting the user agent makes sense of course, which I missed)