[vlc-devel] Using VLC 4.0.0 on WSL2 Ubuntu 25.04 with wayland

[Fatih Uzunoğlu]

 > The SHM module was already using the viewporter in 3.0

The SHM module should handle fractional scale if it is using viewporter. 
My understanding from the protocol and this crash is that whatever 
entity using viewporter needs to handle fractional scale as well. This 
probably means that it should be moved from the interface to the display 
module to prevent conflicts like this, and certainly the higher priority 
EGL module should support that as well (not only SHM).

 > A provider cannot use *any* rendering service on the surface unless 
it can't conflict with *any* potential use by *any* display.

As I said, I'm willing to not use viewporter in the interface, but what 
is the alternative at the moment? I don't think not supporting 
fractional scale in 2025 is a good alternative. I used it in the 
interface because, 1) I'm more familiar with it than the display 
modules, and 2) the buffer scale was already set there 
(`wl_surface_set_buffer_scale()`), it only made sense to handle 
fractional scale there as well.

 > If triggering a crash in preexisting working merged code is not 
breaking it, then I don't know what is.

We introduced a condition in Qt interface that we use viewporter, like 
the fractional protocol says, to support fractional scale in order to 
fit the video window properly. This did not require modifying the SHM 
module to cause crashes without the interface. This is problematic with 
the interface embedding in use, and it should be fixed if possible.

 > No, you just made that up. Can you even point to a precedent for that 
bold misleading claim?

There is no guarantee that window embedding must be possible with all 
cases. I remember the `EGL_KHR_display_reference` case for example, 
which was a requirement for embedding.

There can be a variety of configuration that can potentially make 
embedding impossible. This does not mean that these configuration should 
not exist, just to satisfy embedding in all cases. If in some situations 
video embedding is not possible, they should not be enabled or offered 
when the interface is used. I do not know if with the SHM module 
viewporter is the only issue, but as I said, we should try to support as 
many configurations as feasible in my opinion.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/vlc-devel/attachments/20250623/75907d17/attachment.htm>