Structuring CSS Stylesheets

[David Grieve]

On 8/15/16 9:46 AM, Daniel Glöckner wrote:
> Hi,
>
> We recently came across a number of performance issues which were caused by our poor CSS.
>
> Our stylesheet contained too many selectors, specifically too many generic selectors targeting "common" JavaFX controls (.text, .label etc.).
Make the selectors as specific as possible. Avoid the universal selector 
'*' if you can.
>
> We found the culprits by patching the JRE, adding some statistics to SimpleSelector and CompoundSelector. I was wondering whether there are easier ways but anyway, it works ;)
This sounds like some code that would be good to share with the 
community. :)
>
> We've meanwhile improved our CSS performance (by making a bunch of selectors more specific) but want to re-structure the stylesheets to be more future-proof (with even better performance ;)).
>
> Could you quickly comment on the following idea?
>
> Our CSS is already divided into several stylesheets (e.g. table.css, some-dialog.css etc.).
> These stylesheets are all imported via @import into a global theme.css. theme.css is then added to the scene.
>
> We're thinking about adding the individual stylesheets only to nodes which need them, for example our UI component factory would add table.css to a TableView's list of stylesheets (tv. getStylesheets().add("/path/to/table.css"). The global theme.css would be minimal and only define colors and fonts.
>
> What do you think about this approach? Will this work nicely with caching of CSS styles in JavaFX?
I think if you are going to go this route, you might want to use 
Region#getUserAgentStylesheets() which adds the styles as user-agent 
styles. But I don't think it will buy you much in terms of CSS performance.

If you the biggest bang for your buck relative to JavaFX CSS 
performance, avoid style lookup and relative font sizes.

>
> Kind regards,
> Daniel