[PATCH 0/2] Support for high DPI outputs via scaling

[Bill Spitzak]

John Kåre Alsaker wrote:
> 
>     I expect a compositor to render deviations of the desired scaling
>     factor without scaling windows. The range when this is allowed is
>     reported to clients so they can try to render at a size which will
>     avoid scaling.
> 
>     For example a compositor may want to use a 1-1.2 range with 1.1 as
>     the desired scaling factor. A clients which are only able to draw at
>     integer scaling factor would round that up to 2 and let the
>     compositor downscale it. When the range for which compositor won't
>     scale is send to clients we can avoid this.

I don't think a range is necessary. The client can just claim that it's 
window is scaled at 1.1 even though it drew it at 1. Or at 2.2 even 
though it drew it at 2. Nothing stops the client from doing this so you 
might as well make that the way integer scales are done.

With the range, what happens to a surface with a scale of 1.3? Is it 
scaled by 1.3? Or should it be 1.3/1.2 times larger than the one scaled 
at 1.2, which is actually 1.191666? For this reason I think any scale 
wanted by the client should be obeyed literally.

> We may also allow scaling factors below 1.

I think scaling factors less than 1 are going to be a requirement. 
Otherwise the "units" have to be for the lowest-resolution device, which 
seems silly if you have a huge hi-res screen and a small lcd low-res 
display on your keyboard.