[PATCH 00/15] weston scaling support

[John Kåre Alsaker]

On Wed, Jun 5, 2013 at 3:11 AM, Bill Spitzak <spitzak at gmail.com> wrote:

> John Kåre Alsaker wrote:
>
>  This is still a problem without any high-DPI stuff. You could just as
>> easily have an input device with a resolution 3 times higher than the
>> display.
>>
>
> I am worried that most clients will work around the problem of the scale
> proposal by rounding all numbers from 3.5 to 4.5 to 4, thus throwing away
> the high resolution input device.
>
> Lets assume a screen has scale 3 and there is a pointing device with a
> resolution of 1/2 of these pixels. And the client is drawing a full-res
> surface.
>
> (note the numbers here looks strange but they are the closest decimal to
> the 24.8 fixed-point values. That is why it is .332, not .333):
>
> Under your proposal a normal pointing device will return 1, 1.332, 1.664,
> 2, ... as coordinates. If the client just blindly multiplies by 3 they will
> get 3, 3.996, 4.992, 6. I think most clients will fix this by rounding to
> the nearest integer to get 3, 4, 5, 6.
>
> Now the high-resolution device will return 1, 1.164, 1.332, 1.5, 1.664,
> 1.832, 2. If the client blindly multiplies these by 3 they will get 3,
> 3.492, 3.996, 4.5, 4.992, 5.496, 6. However if the client rounds (possibly
> because the author never saw a high-resolution pointer) they will get 3, 3,
> 4, 4, 5, 5, 6, thus losing the high-resolution.
>
> In my proposal a normal pointing device will return 3, 4, 5, 6. The client
> will not need to round. The high-resolution device will return 3, 3.5, 4,
> 4.5, 5, 5.5, 6. Since the client does not round, it will get these values
> correctly.
>
> Of course the client could only round numbers that are "close" to
> integers, but I still feel my solution is simpler.
>
You might have me confused for Pekka or Alexander. Our proposals should be
identical here. I'm just saying that it will increase the possibly
resolution of input events on higher scaling factors, which reduces issues
with rounding, but doesn't solve it altogether.
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