Why EDID is not trustworthy for DPI

Michel Alexandre Salim salimma at fedoraproject.org
Thu Oct 6 13:57:38 UTC 2011

On 10/05/2011 07:49 PM, Matthew Garrett wrote:
> But what about the single monitor case? Let's go back to your Vaio. It's 
> got a high DPI screen, so let's adjust to that. Now you're happy. Right 
> up until you plug in an external monitor and now when you run any 
> applications on the external display your fonts are twice the size they 
> should be. WOOHOO GO TEAM of course that won't make us look like 
> amateurs at all. So you need another heuristic to handle that, and of 
> course "heuristic" is an ancient african word meaning "maybe bonghits 
> will make this problem more tractable".
Heh, I don't know about Adam's Vaio, but mine (the now-discontinued 13"
Y, a.k.a. Vaio-S-with-ULV-without-optical-drive) has all sorts of
strange quirks (e.g. totally broken ACPI backlight interface; Matthew
would remember this) -- and it turns out that it did what ajax noted
earlier too: xrandr reports a 0x0 physical screen size. *sigh*. So much
for quality products.

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.

Michel Alexandre Salim
µblog:      http://identi.ca/hircus
GPG key ID: 78884778

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