DAD: Dynamic Attribute Dialogs

The text widget is a tex viewer/editor that operates on a string that may contain multiple lines.

Helper macro for widget creation

PCB_DAD_TEXT(table, user_ctx) creates a new text widget and installs user context.

User callbacks

The only callback the user may provide is user_free_cb which is called when the text widget is destroyed. Other than this, DAD caller code can not react on events happening in the text.