On Wed, 2023-06-28 at 10:54 +0300, Pekka Paalanen wrote: > On Wed, 28 Jun 2023 10:41:06 +0300 > Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: > > > On Wed, 28 Jun 2023 01:21:27 -0400 > > Zack Rusin <zack@xxxxxxx> wrote: > > > > > From: Zack Rusin <zackr@xxxxxxxxxx> > > > > > > Atomic modesetting code lacked support for specifying mouse cursor > > > hotspots. The legacy kms DRM_IOCTL_MODE_CURSOR2 had support for setting > > > the hotspot but the functionality was not implemented in the new atomic > > > paths. > > > > > > Due to the lack of hotspots in the atomic paths userspace compositors > > > completely disable atomic modesetting for drivers that require it (i.e. > > > all paravirtualized drivers). > > > > > > This change adds hotspot properties to the atomic codepaths throughtout > > > the DRM core and will allow enabling atomic modesetting for virtualized > > > drivers in the userspace. > > > > > > Signed-off-by: Zack Rusin <zackr@xxxxxxxxxx> > > > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > > > Cc: Maxime Ripard <mripard@xxxxxxxxxx> > > > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> > > > Cc: David Airlie <airlied@xxxxxxxx> > > > Cc: Daniel Vetter <daniel@xxxxxxxx> > > > Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx> > > > > Hi Zack, > > > > I still do not see any UAPI docs for the new properties in this patch? > > If you are wondering what there could be to write about, maybe this can > give a good mindset: > > Let's assume that I am a Wayland compositor developer who has never used > "hotspots" with KMS UAPI before. As I have never tested anything in a > VM, I have no idea why the kernel would ever want to know about cursor > hotspots. Display hardware never does anything with that, it just puts > the cursor plane where I tell it to and composes a single image to be > sent to the sink. The virtual driver VKMS does the same. To me, a > cursor plane is just another universal plane that may have weird > stacking order, pixel format, and size limitations. > > Ideally the doc for HOTSPOT_X and HOTSPOT_Y documents not only their > possible existence and allowed/expected values, but also the reasons > to have them and what they are used for, and that if the properties > are exposed they are mandatory to program in order to use the plane. Instead of resending the entire series maybe I can draft a possible doc below and see if we like it (once we're ok with I'll send out v5 which hopefully will be good). How about: /** * @hotspot_x_property: property to set mouse hotspot x offset. * * Hotspot is the point within the cursor image that's activating * the click e.g. imagine an arrow cursor pointing to bottom right - * the origin coordinate for that image would be top left * but the point which would be propagating the click would be * the bottom right cursor position (crtc_x, crtc_y) + hotspot * coordinates which for bottom right facing arrow would probably * be (cursor_width, cursor_height). * * This information is only relevant for drivers working on top * of para-virtualized hardware. The reason for that is that * the hotspot is fairly encapsulated in the system but imagine having * multiple windows with virtual machines running on servers * across the globe, as you move the mouse across the screen * and the cursor moves over those multiple windows you wouldn't * want to be sending those mouse events to those machines, so virtual * machine monitors implement an optimization where unless the mouse * is locked to the VM window (e.g. via a click) instead of propagating * those mouse events to those VM's they change the image of the native * cursor to what's inside the mouse cursor plane and do not interact * with the VM window until mouse is clicked in it. * * In order for that click to correctly and seamlessly propagate * between the native and virtual machine, not only the cursor image * but also the hotspot information has to match between them. * * Make sure to set this property on the cursor plane if you'd like * your application to behave correctly when running on * para-virtualized drivers (qxl, vbox, virtio or vmwgfx). * / z
