On Tue, Jun 4, 2013 at 10:24 PM, Bill Spitzak <spit...@gmail.com> wrote:
> John Kåre Alsaker wrote: > > And I'm worried that high-resolution pointing devices will be >> ignored by clients that immediately round to the nearest buffer pixel. >> >> Presumably they wouldn't use the high-resolution for anything then. I'm >> not sure how this relates to the topic either. >> > > A client has to round event if it wants to do high-resolution, because it > wants to align positions with things in the buffer. This gets pretty > important with 3D modelling, lots of users and software assume that the > mouse will stop on exactly the same fractional positions, and under your > proposal this would change. > > For instance if there is a low-res device and a scale-3 output, then a > client doing a hi-res display will get mouse positions of 1, 1.333.., > 1.666..., in that window. If there is no low-res device and the hi-res one > now has a scale of 1, then the client will get positions of 3,4,5. > > Multiplying the 24.3 fixed-point representation of 1.333.. by 3 gets > 3.996. The client has to round this to 4 or it will align things slightly > different on one system than the other. I can assure you that this > difference is very annoying in 3D software. > > The only solution is to figure out the resolution of the pointing device, > transform the fixed-point event positions to the buffer positions, and then > round to the nearest multiple of the pointing device resolution. I think a > lot of software will ignore the "figure out the resolution of the pointing > device" step and just assume it is 1 pixel. Therefore any possible > high-resolution pointing will be thrown away. > > Getting the events in buffer pixels would make it a lot easier as they > could be used unchanged. Clients could then just assume any fraction is due > to a high-resolution pointing device. > 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.
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