Why EDID is not trustworthy for DPI

Nicolas Mailhot nicolas.mailhot at laposte.net
Thu Oct 6 15:27:33 UTC 2011

Le Jeu 6 octobre 2011 15:37, Matthew Garrett a écrit :
> On Thu, Oct 06, 2011 at 01:13:21PM +0200, Nicolas Mailhot wrote:
>> Le Mer 5 octobre 2011 23:35, Matthew Garrett a écrit :
>> > This... works badly. Really. Open gimp and add some text. Now double the
>> > size of the font. Save the image and open it in image viewer, and zoom
>> > out so the text is half the size. It doesn't look the same as your
>> > original text.
>> >
>> > Rendering fonts (and even SVGs) well requires you to know the scale that
>> > you're rendering to. More pixels mean you can add more detail. If you
>> > shrink that then the additional detail is still there, getting in the
>> > way of the actually important information. Doing this properly requires
>> > that the original object renderer be part of the scaling process, and
>> > doing that on the fly with reasonable performance just isn't part of our
>> > rendering stack at the moment.
>> Which is exactly why forcing 96dpi on displays which have very different
>> pixel
>> densities *today* is not a good idea at all.
> Knowing the number of pixels available means that the output will be
> legible, even if you'd prefer it to be a different size.

I don't call text which is significantly too big or too small legible.

When apps that use different toolkits perform different font size adjustments,
the resulting UIs are inconsistent and generally tiring (uniformity is a huge
factor in text readability)

When basic font sizes are out of whack because the desktop pretends the pixel
density is way different than it is really users try to compensate using all
the available size settings in their apps. The result is a huge heterogeneous
mess. Settings and documents can not be moved from one computer to another
without strange font size changes. Different fonts are not adjusted the same
way by users, because of size rounding in UIs, breaking font set harmony.
Sometimes you get apps that adjust via zooming without re-rendering

Nicolas Mailhot

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