<div dir="ltr">Mouse input is reported in a 24.8 fixed-point format. Subpixel mouse locations are entirely possible. </div><div class="gmail_extra"> <div class="gmail_quote">On Mon, Mar 9, 2015 at 10:33 PM, microcai <<a href="mailto:microcai@fedoraproject.org" target="_blank">microcai@fedoraproject.org</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">在 2015年3月9日 Monday 08:59:35，您写道： > You misunderstood what pq said. > > You work in "logical pixels". On a hi-DPI display, with twice the pixel > density, each "logical pixel" is backed by 4 device pixels. Your actual > backing surface containing the pixels is in "device pixels". > > So, if you have an window that is 800x600 logical pixels, when you drag it > to a low-DPI display, your backing buffer is 800x600 device pixels. When > you drag it to a hi-DPI display, your backing buffer is 1600x1200 device > pixels. So mouse input is reported in logical pixels, and the logical pixels is not floating point numbers, resulting lost information when the surface are on hidpi display. <div class="HOEnZb"><div class="h5"> > > When you submit your buffer, you tell the compositor what the ratio of > device pixels to logical pixels is, in the perhaps misnamed > "set_buffer_scale" request. So, for the low-DPI buffer, you submit "1", > since 800x600 / 800x600 = 1. When you submit your hi-DPI buffer, you submit > "2", since 1600x1200 / 800x600 = 2. > > If you submit "1" and you are on a low-DPI display, it all matches and > things are fine. If you submit "1" and you are on a hi-DPI display, the > compositor scales up your buffer to match. If you submit "2" and you are on > a hi-DPI display, it all matches up and things are fine. If you submit "2" > and you are on a low-DPI display, the compositor scales down your buffer to > match. > > On Mon, Mar 9, 2015 at 6:19 AM, microcai <<a href="mailto:microcai@fedoraproject.org">microcai@fedoraproject.org</a>> wrote: > > 在 2015年3月9日 Monday 10:39:20，您写道： > > > > > Hi, > > > > > > On Monday, March 9, 2015, microcai <<a href="mailto:microcai@fedoraproject.org">microcai@fedoraproject.org</a>> wrote: > > > > so we are forcing two code pathes in APP? or just support non-integer > > > > scale? > > > > > > Scaling is a specific fallback for legacy/non-DPI-aware clients, to get > > > them to show anything at all. Other clients will render at the > > > > appropriate > > > > > resolution already. > > > > That's not the story I was told. pg says scale is the *only way* to > > support > > HiDPI. > > > > > Any plan that relies on integer scaling means you're wasting pixels on > > > > your > > > > > lovely dense display. Any plan that relies on non-integer scaling makes > > > your text blurry to the point of unreadable - again, a waste of pixels > > > on > > > such lovely displays. Just render at the correct scale to begin with. > > > > > > Cheers, > > > Daniel > > > > _______________________________________________ > > wayland-devel mailing list > > <a href="mailto:wayland-devel@lists.freedesktop.org">wayland-devel@lists.freedesktop.org</a> > > <a href="http://lists.freedesktop.org/mailman/listinfo/wayland-devel" target="_blank">http://lists.freedesktop.org/mailman/listinfo/wayland-devel</a> </div></div></blockquote></div> -- <div class="gmail_signature"> Jasper </div> </div>