[PATCH weston 4/8] protocol: crop & scale RFC v3

Bill Spitzak spitzak at gmail.com
Fri Nov 29 01:20:21 PST 2013

Okay I think perhaps I am completely failing to comprehend what is going on.

The client I am thinking of is not trying to do "partial pixels". What I 
am thinking of is the most simple client you can imagine that knows what 
the output_scale is and decides it wants to render images at full 

If for instance the output_scale is 3, then I think the client will set 
the buffer_scale to 3, and then the pixels in the client's buffer will 
map 1:1 to the pixels on the output device. There are no "partial pixels".

If this client wants a rectangle that is covered by an image produced by 
this scaling extension, it appears to me that it cannot be any integer 
number of buffer pixels. It can only be multiples of 3 pixels in both 
size and position.

Please correct me if I am misunderstanding this, but I have read it over 
and over and over and it sure looks like this is what the design does!

On 11/27/2013 01:51 PM, Daniel Stone wrote:
> Hi,
> On 27 November 2013 20:08, Bill Spitzak <spitzak at gmail.com> wrote:
>> On 11/27/2013 12:34 AM, Pekka Paalanen wrote:
>>> I have explained all this before. Nothing here has changed.
>> I realize this but I still have to express my complete dumbfoundment that
>> you think this is ok.
> You're attempting to design for the problem space where clients create
> configurations which cannot be displayed except by attempting to
> invent the concept of 'partial pixels', where a buffer size of
> 79.3333... is not only meaningful but a design goal.  The opposing
> position is 'don't do that': clients should avoid getting themselves
> into these situations in the first place.
> Your proposals really come across as attempting to design for
> situations which should never occur (and can't meaningfully be dealt
> with by extant hardware), optimising for hugely misguided clients in a
> fit of completism.  That's your view, which you've made very clear,
> but I don't think it's shared by anyone else in these threads.
> Cheers,
> Daniel

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