Screen resolution is not saved

Ticket https://gna.org/task/?7267 deals with the problem of using the correct video driver in Xorg configuration when a single video chipset from Intel, nVidia and eventually ATI is detected. In case of a complex video configuration (several chipset) or another chipset vendor advanced users may need to modify their Xorg configuration file but their work will be wiped at next reboot even if full persistence is activated (dexconf is run at each boot).

We propose to modify dexconf so that it uses hardware signatures to generate the Xorg configuration or to retrieve a previous one. For example the following command signs the combination of video chipset and monitor information:

$ sudo ddcprobe | md5sum | cut -d ' ' -f 1
2c4bf5d7007d7687a8a2390ba8638b3f

We may also want to add lspci information:

$ echo $(sudo ddcprobe) $(lspci -m | grep -i vga) | md5sum | cut -d ' ' -f 1
49db59228af17b4667ac033f9963299c

Note that lspci also reports PCI slots so if you change your video card of slot, the MD5 signature changes too.