[webkit-dev] Accept- & Content-Resolution headers proposal
robburns1 at mac.com
Thu Jun 7 15:07:52 PDT 2007
On Jun 7, 2007, at 3:52 PM, 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? 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.
> 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.
> 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.
It seems that you're not reading the proposal. This does call for
the client to use whatever algorithm it deems appropriate to request
an image of a certain pixel dimension (though I think my copy of
Nicholas example may have read ppi, I meant to list pixel dimension).
In any event, the server works to accommodate the client. This isn't
meant to help the client determine the absolute dimensions its meant
to deliver efficiently sized content. If its too large, it waists
bandwidth (at a UI responsiveness degrading moment) and then gets
down-sampled by the client anyway. If its too small, it may look
poor. CSS will not solve this (except for CSS related images). It
needs content negotiation. And even for CSS with media queries, this
is even more flexible.
Also, as I said before media queries do not accomplish what you're
saying they accomplish. They don't leave things in the hands of the
client, they're in the hands of the author. So if the author (maybe
years before), decides to deliver an image of a certain size to the
client, that's what the client gets. WebKit isn't going to be able to
request a different size. Presumably the authro will make it
appropriate for the client (based on the media query), but the author
does no necessarily know anymore about WebKit's image processing
capabilities (whether it prefers an image twice the size to one a
little smaller than the requested size). So the solution proposed
here actually puts more control in the clien't's hands than CSS media
queries (unless the client starts lying about its meda environment,
but I don't think that would be good practice).
PS, again my suggestion is for the client to request specific pixel
dimensions for the media not the ppi/dpi/cmpi) If the the UA is in an
environment with multiple displays or multiple resolution output of
any kind it can use that in determining the pixel dimensions to
request. Otherwise, it can re-request the image for the new output
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