After a discussion with Kyatric on IRC, here's a new plugin : UITemplates.
<img src="http://dl.dropbox.com/u/1412774/UITemplate/demo.png" border="0">
Do you miss the various "Layout" objects from Java/SWING, allowing you to have a "bag" in which you throw some widgets, and the "Layout" object arranges everything onscreen for you (you can have GridLayout, a FlowLayout, and a lot of other elastic Layouts).
This plugin is there to do the same. I renamed the whole thing "Templates", to avoid confusions with C2's layouts.
For the beginning, there's only GridTemplate. You can specify a number of rows/columns, the inner padding in pixels from the border, and at widgets.
Currently, it only works with objects added at runtime (I still need to understand how to add objects create at editime without breaking everythin). It doesn't work also with HTML objects (Button, TextBox, HTML_Div, etc..), because those are using CSS to style themselves.
The demo : http://dl.dropbox.com/u/1412774/UITemplate/index.html
The plugin : http://dl.dropbox.com/u/1412774/UITemplate/pode_UITemplates.0.1.zip
As always, Critics&Comments are welcomed !
Edit : I forgot to say it, but : thanks a lot to (French)Yann for is ]sliders example code ! <img src="smileys/smiley2.gif" border="0" align="middle">