Thanks, it looks exactly like it. Now just have to see how to make it work with Qt but that's another question :)
Kind regards, Jean-Michaël On Mon, Apr 26, 2021 at 5:08 PM Jonas Ådahl <jad...@gmail.com> wrote: > On Mon, Apr 26, 2021 at 04:57:01PM +0200, Jean-Michaël Celerier wrote: > > Hello, > > I am working on the multimedia sequencer ossia score (https://ossia.io). > > > > I am trying to make sure that it works fine for Linux users under > wayland. > > > > For audio (and in general multimedia) apps, there is a very common family > > of GUI widget which allows to scroll a value "infinitely" (or at least > much > > more than the height of the screen) - the usual user interaction is : > > * User clicks on the widget : the mouse cursor disappears (some apps will > > give a kind of highlight to the widget to indicate that it is being acted > > upon) > > * User moves their mouse upwards or downwards to increase the value > > * At some point they reach the top or the bottom of the screen : to > > continue scrolling transparently, the app translates the mouse cursor to > > the top of the screen > > * When the user releases the mouse the cursor reappears at the position > > where it was clicked. > > > > This is needed in two case : > > - To make sliders / knobs with easily adjustable values > > - To implement infinite- or at least very long scrolling in minimaps. > > > > I made a few videos: > > - Video 1: example of slider with the feature in Ableton Live (one of the > > most used music making app) : https://streamable.com/ecepvc > > > > - Video 2 : example of minimap in Ableton Live : > > https://streamable.com/epc7r1 > > > > - Video 3 : Example of the pain induced by software that do not support > the > > feature: here I want to change the tempo but cannot because the mouse > hits > > the top of the screen. Thus I have to release and go click on it again : > > https://streamable.com/bniht5 > > > > Thus, my question is : what must I do as the developer of such an app to > > make sure that my users will have widgets that will work "as expected" > for > > people in the media creation field, whatever the wayland compositor my > > users are using (KDE Plasma, GNOME, sway...). I don't want them to have > an > > inferior user experience on Linux when compared to other operating > systems. > > > > The googling I've done so far seems to say that there is no way to > position > > the cursor absolutely directly through wayland, but the only other way > > seems to be through /dev/uinput which needs root permissions to write to > > (and my userbase are artists who generally don't have the technical > > skillset to know that they must mark things as root; I could always check > > and show a popup that requests the user to do chmod u+rwx on /dev/uinput > on > > startup but that would be my last resort...) > > To implement the behavior shown in video 1 and 2, the "Wayland" way is > depends on two protocols extension: > > * Pointer locking extension[0] > * Relative pointer motions extension[1] > > With the core wl_pointer protocol object, you can control when the > pointer cursor sprite is showing or not; with the pointer locking > extension, you can effectively lock the pointer position to its > position, meaning it will stay put and won't "escape" your application > window; and lastly, with the relative pointer motions extension, you can > receive pointer motions that are not affected by actual movement of the > pointer cursor sprite, i.e. even if the pointer hit an edge or doesn't > move, you'll still receive the motions as sent from the device. > > I think most compositors support these two protocol extensions as they > are a corner stone in how e.g. 3D FPS games work. > > > Jonas > > [0] > https://gitlab.freedesktop.org/wayland/wayland-protocols/-/blob/master/unstable/pointer-constraints/pointer-constraints-unstable-v1.xml > [1] > https://gitlab.freedesktop.org/wayland/wayland-protocols/-/blob/master/unstable/relative-pointer/relative-pointer-unstable-v1.xml > > > > > Thanks ! > > Jean-Michaël > > > _______________________________________________ > > wayland-devel mailing list > > wayland-devel@lists.freedesktop.org > > https://lists.freedesktop.org/mailman/listinfo/wayland-devel > >
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