AddNewIDLFile.md

Adding a new IDL file

Serenity's build system does a lot of work of turning the IDL from a Web spec into code, but there are a few things you'll need to do yourself.

For the sake of example, let's say you're wanting to add the HTMLDetailsElement.

1. Create LibWeb/HTML/HTMLDetailsElement.idl with the contents of the IDL section of the spec. In this case, that would be:

[Exposed=Window]
interface HTMLDetailsElement : HTMLElement {
    [HTMLConstructor] constructor();

    [CEReactions] attribute boolean open;
};

2. If the IDL refers to other IDL types, you need to import those. For example, CSSRule has an attribute that returns a CSSStyleSheet, so that needs to be imported:

#import <CSS/CSSStyleSheet.idl>

interface CSSRule {
    readonly attribute CSSStyleSheet? parentStyleSheet;
};

3. If the IDL starts with [Exposed=Window], add the following to LibWeb/Bindings/WindowObjectHelper.h:

   • #include <LibWeb/Bindings/HTMLDetailsElementConstructor.h> and
   • #include <LibWeb/Bindings/HTMLDetailsElementPrototype.h> to the includes list.
   • ADD_WINDOW_OBJECT_INTERFACE(HTMLDetailsElement) \ to the macro at the bottom.

4. Add a libweb_js_wrapper(HTML/HTMLDetailsElement) call to LibWeb/idl_files.cmake

5. Forward declare the generated classes in LibWeb/Forward.h:

   • HTMLDetailsElement in its namespace.
   • HTMLDetailsElementWrapper in the Web::Bindings namespace.

6. The C++ class equivalent of the IDL interface has a few requirements:

   • It must inherit from public RefCounted<HTMLDetailsElement> and public Bindings::Wrappable
   • It must have a public using WrapperType = Bindings::HTMLDetailsElementWrapper;

7. If your type isn't an Event or Element, you will need to add it to is_wrappable_type() so that it can be accepted as an IDL parameter, attribute or return type.