The bug has been reported for some time and it's related to panels that display breadcrumbs.
Here is what these breadcrumbs mean in context of a panel.
- HTML displays XPath for the selected element.
- Script shows the stack trace when hanging on a breakpoint.
- DOM displays the position of the selected object within DOM hierarchy.
The problem appeared when the breadcrumb information was so long that it went off the screen. Here is an example of the Script panel with long stack trace.
See, the stack trace even pushed the debugger buttons of the panel and it's only possible to debug using keyboard.
Here is the fixed version.
The HTML (and DOM) panel is also fixed, in case of a deep hierarchy of elements (and long XPath) there are, again, a little arrow buttons that allow to scroll and see the entire value.
Note that scrolling can be done by:
- clicking on the small arrow
- moving mouse over the small arrow
- using mouse wheel
- using keyboard (you need to check Enable Accessibility Enhancements in Firebug options)