That would cause things to be a little weird when the screens are at different resolutions, especially different aspect ratios. When a window opens, it has to pick a size to open at. A pixel size if I am thinking correctly. The problem is, which pixel size should it use.

I am guessing that the software could handle scaling the size to make things work on different resolutions such as 800x600 vs. 1024x768. Scaling and distorting is beyond its capabilities.

I've configured dual monitor whit clone option, desktop is shown on both monitors but ... there is a little problem!
Whit xrandr, I set the resolution to 1280x800 on laptop monitor (native resolution) and to 1024x768 on external monitor.
The problem is that, for example, the panel is cut to 1024: a good choice for external monitor (it fits perfectly) but an horrible problem for the laptop monitor where the panel becomes too short!!
Moreover, if I open a pdf file on my laptop, it fits all the space on the internal monitor, that is 1280x800: of course, on the external monitor my pdf becomes shrinked!!

This is the main problem, a really strange behavior that I don't understand!! I don't know if it depends by xfce or by my xorg configuration, but I'd like to know that!
Please, there is somenone that can help me?

Thanks in advance.

Michele