Why EDID is not trustworthy for DPI

[Robert Marcano]

On 10/06/2011 09:45 AM, Matthew Garrett wrote:
> On Thu, Oct 06, 2011 at 03:57:38PM +0200, Michel Alexandre Salim wrote:
>
>> But maybe a quick 'I know I have a 13.3" widescreen laptop, you know the
>> resolution, just make things work' should work for the single-screen
>> case (esp if we stick to certain target DPIs as Adam suggested). One
>> shouldn't ask the typical user for information that's too cumbersome to
>> use, oui? Like asking them to use a physical ruler to match up against.
>
> Like I said, that works fine right up until the point where you plug in
> a monitor with a different DPI. What do we do then?
>

Use the same DPI of the main monitor? what is the difference of using 
the wrong DPI obtained from the main monitor on the external one and 
using the hardcoded 96 value when the external monitor is not 96dpi. 
both are wrong without solution, why not at least give the user the 
option to set the correct DPI for the internal one, using 96 as default