Logical flaw with stylesheets for Markdown

[InAnYan]

Context
I've been trying to integrate your component to JabRef. In the app we provide a custom CSS file, that is automatically loaded and updated into Scene (it's called Base.css). The app also has theming change. This change is also handled, and to the scene a new additional CSS file is loaded (for example Dark.css).

The problem
The thing is, I couldn't use this features with your MarkdownView controller, and I think the error is like this:

Look how CSS stylesheets are loaded to the component:

1. Base.css is loaded into Scene.
2. MarkdownView will inherit this Base.css.
3. (!) MarkdownView will load mdfx.css file and overwrite the styles.
4. MarkdownView will also load mdfx-default.css if getDefaultStylesheets is not overriden.

Workaround
And in order to solve this issue, we needed to overwrite the getDefaultStylesheets to include our Base.css or Dark.css. The flow of CSS looks like this: Base.css -> mdfx.css -> Base.css. And only that will work.

Interpretation
So instead of inheriting the CSS files already loaded to Scene and use it from the bottom, we are forced to add it again on top.

Proposed solution

• Do not load mfdx.css (or load this not in constructor, but in getDefaultStylesheets).
• If users want to provide their style, force them to provide all the classes that are present in mfdx.css and mdfx-default.css

[dlemmermann]

The markdown view is simply a custom controls and custom controls need to load their own stylesheets via getUserAgentStylesheet(). It is as simple as that. NEVER add stylesheets to a custom control via getStylesheets().add(..). That is just wrong. I also do not see a need to split the styles into two files. I have reported this issue before and now decided to copy the entire code base into my own project and make this little change myself.