Test that `src/diagrams/*/styles.ts` module returns a valid
CSS stylesheet that can be parsed via [stylis][1] and then
becomes a valid CSS that [csstree-validator][2] validates.
We test this for every diagram and for every theme, because
many of the invalid CSS bugs are caused by missing theme vars.
There are some CSS errors that I couldn't easily fix, so I've written
the tests to ignore the following CSS errors:
- 'Unknown property `rx`' (Valid in SVG2 draft and in some browsers)
- 'Unknown property `ry`' (Valid in SVG2 draft and in some browsers)
- 'Unknown property `dy`'
- This doesn't seem to be valid CSS in any SVG version, but maybe
some browsers support it 🤷 I feel like we should probably change
this though.
[1]: https://github.com/thysultan/stylis
[2]: https://github.com/csstree/validator
The `scaleLabelColor` variable in `theme-forest` and `theme-neutral`
was set to `"calculated"`, as it defaults to `this.labelTextColor`
**before** `this.labelTextColor` was set.
Moving the `this.labelTextColor` assignments before `scaleLabelColor`
is calculated fixes this.
Fixes mindmap and timeline invalid CSS in theme forest and neutral.
Define `excludeBkgColor` for `theme-dark` to fix invalid CSS
for gantt diagrams.
All the other themes defined this to '#eeeeee', but I thought that
was a bit too bright in a dark theme, so instead I set it to
`darken(this.sectionBkgColor, 10);`.
`border2` is a theme variable used by the CSS for flowcharts and
user-journey.
I've defined this to default to `tertiaryBorderColor` in theme-base,
as other themes tend to set `border2` to the same value as
`clusterBorder`, which in theme-base is `tertiaryBorderColor`.
Define `arrowheadColor` as `invert(this.background)` in
`theme-base.js`, as it's currently `undefined`, which causes CSS
issues when using `theme-base`.
I've picked `invert(this.background)` so that it matches
the default value of `lineColor`.
Currently, `requirementBorderSize` defaults to `primaryBorderColor`,
which is a color, not a valid SVG `stroke-width`.
Instead, I've made it default to `1`.
Fix an invalid value for the CSS `fill-opacity` value.
Percentage values for `fill-opacity` are only supported in the SVG 2.0
draft, so according to [MDN][1]:
> it is not widely supported yet, […] as a consequence, it is best
> practices [sic] to set opacity with a value in the range `[0-1]`.
[1]: https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/fill-opacity
