On Thu, Mar 19, 2020 at 1:58 PM Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: > > On Thu, 19 Mar 2020 12:49:27 +0100 > Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > > Hi, > > > > On 3/19/20 11:00 AM, Pekka Paalanen wrote: > > > On Wed, 18 Mar 2020 15:28:02 +0100 > > > Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > > > > >> ATM the Atomic KMS API lacks the ability to set cursor hot-spot > > >> coordinates. Mutter (and Weston) have tried to emulate this by shifting > > >> the coordinates for where to draw the cursor by the hotspot-coordinates > > >> and always using 0x0 for the hotspot. > > >> > > >> But this breaks the so called "seamless mouse mode" for virtual-machines > > >> and there really is no way to fix this but to allow passing the proper > > >> hotspot coordinates to the virtual gfx-card. > > >> > > >> Seamless-mode consists of 2 parts: > > >> > > >> 1) Letting the VM-viewer window-system draw the cursor as it normally > > >> would draw it. > > >> > > >> 2) Giving absolute coordinates of the mouse to the VM by e.g. emulating > > >> an USB drawing tablet. These coordinates come from translating the > > >> coordinates where the VM-viewer window-system is drawing the cursor > > >> to an absolute position using the top left corner of the view as 0x0 > > >> and the bottom right corner as max-abs-x,max-abs-y. > > > > > > Hi, > > > > > > is the VM-viewer then hiding or autonomously moving what the display > > > server inside VM has put on the KMS cursor plane? > > > > Yes and no, it is not the VM-viewer which is hiding what the > > display-server inside the VM has put on the KMS cursor plane, > > the VM-viewer negotiates seamless mouse mode with the hypervisor > > and then the hypervisor just ignores the cursor-plane except for > > sending "sprite" changes to the VM-viewer. > > Hi, > > I don't think I understand what you're saying, but I assume that I was > right in that the VM cursor plane content will not be shown always > exactly in the very position the compositor inside the VM puts it. > Maybe the example further below explain the issue I envision. > > > > If so, sounds like hilarity would ensue with Weston. > > > > > > Weston does not actually know what a cursor is. Weston will happily put > > > any arbitrary non-cursor content onto the KMS cursor plane if it happens > > > to fit. It's just that usually there is a small surface top-most that > > > ends up on the cursor plane, and that surface accidentally happens to > > > be a cursor by Wayland protocol. > > > > > > It's not difficult to get e.g. weston-simple-shm window to be shown on > > > the KMS cursor plane: just hide the real cursor from the client. > > > > > > No, it's not an oversight. It is called "making maximal use of the > > > available KMS resources" by using KMS planes as much as possible to > > > avoid compositing by rendering with Pixman or OpenGL. > > > > Yes it sounds like this will break with Weston, note that it already > > is broken in Weston, if you run e.g. Fedora 32 beta + its Weston > > package inside a VirtualBox VM then start gnome-terminal (so > > that you get a caret cursor instead of the default one) and try to > > select text. This will result in the wrong text being displayed > > because Weston does not relay cursor hotspot info to the GPU, > > also see: > > https://gitlab.gnome.org/GNOME/mutter/issues/1094 > > > > Where the symptoms of this are described in more detail > > (they are identical for Weston and mutter). > > Right, that's the problem with the hotspot. > > > Fixing this will require the discussed KMS atomic API changes > > and also changes on the Weston and mutter side to pass through > > the hotspot info. > > The problem I am referring to is that to the user looking at the > VM-viewer, suddenly an arbitrary application window (e.g. > weston-simple-shm) starts to act as if it was the cursor, when there is > no real cursor shown. You have a random window unexpectedly moving > around, as if you had started dragging it around with your mouse. > > The only way to fix that is to stop Weston from putting non-cursor > content on the cursor plane. > > It sounds like your VM-viewer makes the assumption that the pointer > input device it delivers to the VM is the one that will control the KMS > cursor plane position inside the VM. Is that right? > > What if the desktop inside the VM is controlled by a remote, e.g. VNC? > Then the input events to the VM are completely unrelated to the > expected motion of the cursor. Do you just tell the users to stop using > the seamless mode in that case? > > What if display servers stop using the cursor plane completely, because > people may hit a case where a VM-viewer makes the wrong assumption about > which input device is associated to which cursor plane inside the VM? Hm that sounds like we should have an additional flag with atomic that enables/disables the hotspot functionality. Then compositors can decide what they want to do with that thing. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
