gobject introspection support in the xwidget branch

[joakim]

I have implemented gobject introspection support[1] in the xwidget branch[2].

See [3] for background information about the xwidget branch.

supporting gobject introspection means that more gtk widgets can be
tried out with less effort, and also that the build process and runtime
support for widgets is easier. The drawbacks are small: somewhat slower
execution, and difficulty in providing elisp bindings for introspection.


In order for GIR to work, it needs the namespace and class of a
  widget. This is used to access the typelib file, which contains the
  introspection data. The namespace and class is stored as a property
  on the lisp symbol handle used by xwidgets to identify the widget
  class.

This snippet sets the needed :xwgir-class property, and calls the
set_zoom_level method:

M-x xwidget-webkit-browse-url RET www.emacswiki.org RET

Then eval the following:

;;load the webkit typelib
(xwgir-require-namespace "WebKit" "2.0")

;;provide the metadata needed so xwgir can work with the webkit-osr xwidget
(put 'webkit-osr :xwgir-class '("WebKit" "WebView"))
;;call the method
(xwgir-call-method (xwidget-at 1) "set_zoom_level" '(3.0))

It's also possible to create widgets dynamically, by using
introspection to call a widget constructor(from xwidget-test.el):


(defun xwgir-test ()
  (interactive)
  (xwgir-require-namespace "Gtk" "3.0")
  (put 'color-selection :xwgir-class '("Gtk" "ColorSelection"))
  
  (xwgir-demo-a-xwgir-button)
  (xwgir-call-method (xwidget-at 1) "set_label" '( "xwgir set label!"))
  )

Current limitation:
- Only 0 arg constructors are supported at the moment. Since xwidgets
  defer construction, the args needs to be stored with the xwidget, and
  this hasn't been done yet.

- xwgir-call-method does indeed lisp to gobject conversion for the
  arguments, but only some primitive types are supported atm.

- next to no argument checking. If wrong type args are used with the
  xwgir methods, emacs crashes.




Footnotes: 
[1]  https://live.gnome.org/GObjectIntrospection/

[2]  bzr branch http://bzr.savannah.gnu.org/r/emacs/xwidget 

[3]  http://bzr.savannah.gnu.org/lh/emacs/xwidget/annotate/head:/README.xwidget

-- 
Joakim Verona