[webkit-dev] Accept- & Content-Resolution headers proposal

[Nicholas Shanks]

On 7 Jun 2007, at 21:52, Andre-John Mas wrote:

> Surely all of this becomes moot if we specify objects in terms of  
> inches, cm or mm, all of which are already supported by css?

Yes, but we want a solution that works where CSS is unavailable, the  
target destination may not be an HTML page either. An example could  
be an application that displays arbitrary images from file: and http:  
URLs. With file: we have metadata available, with http it has to be  
provided along with the image.

> A browser that interprets these 'absolute' units properly should  
> already know what DPI the current environment is in, or have access  
> to the necessary API to display correctly.

Also, some, but by no means all images have pixel dimensions and DPI  
encoded into them, rather than how wide they are in cms. Either set  
of values will do the job though.

> The problem that we have today is that some environments don't tell  
> the application the real DPI, so the application is left guessing  
> and mis-rendering things on screen.

I wrote a webkit patch for that, which has a lot of comments on the  
issue:
http://bugs.webkit.org/show_bug.cgi?id=11644

There was a request for make it conditional on a user preference, but  
the tree got locked down, then I got a job and didn't have time to  
update the patch.

> The other thing that must be taken account is that on a multi- 
> headed computer you may have two screens each with different DPIs.  
> If you were to send DPIs to a server, which one would you use? It  
> is for reasons such as this, that I believe, that it is important  
> that it the responsibility of the local system to work this out,  
> with the appropriates hints from the web page.

I suggest sending the highest DPI and then scale back slightly for  
the lower res screen when windows are dragged across (they won't be  
too different I'd imagine). The patch took the DPI from the main  
display, which is probably the next best thing.

- Nicholas.


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