Xmir root window does not resize reliably

[Christopher Townsend]

Using the newest Xmir from Maarten Lankhorst's PPA (ppa:mlankhorst/ppa) and starting a legacy x app in Unity 8, when resizing the window in Unity 8, the X surface is not updated.

[Daniel van Vugt (vanvugt)]

The required logic that's missing in XMir is to listen for and act on resize events.

First, always get the dimensions from the buffer you're working with to guarantee everything matches...

EGL:
    eglQuerySurface(egldisplay, eglsurface, EGL_WIDTH, &width)
    eglQuerySurface(egldisplay, eglsurface, EGL_HEIGHT, &height)
or
    call mir_surface_get_current_buffer [1] to get the width/height.

Software surfaces:
    The function mir_surface_get_graphics_region [2] if you're using it already returns the width/height in the result structure. Sorry for the confusing API design where both functions [1] & [2] have generic names. I didn't do it.

Idling and waking up on resize:
    Listen for mir_event_type_resize/MirResizeEvent [3] but be sure to ignore the dimensions included in the event, because an annoying race [4] means they might be wrong for the buffer you're working with. You should ignore the dimensions in MirResizeEvent and query the dimensions using any of the above functions instead.

- Daniel

[1] http://unity.ubuntu.com/mir/group__mir__toolkit.html#ga696098fdc7c4a97bab7dedadda3fc212

[2] http://unity.ubuntu.com/mir/group__mir__toolkit.html#gacfcbe5643cc037ddd51414ce28c93529

[3] http://unity.ubuntu.com/mir/struct_mir_resize_event.html

[4] https://bugs.launchpad.net/mir/+bug/1288021

[Daniel van Vugt (vanvugt)]

This bug is still an issue for the Xmir root window. However if you run with -rootless in the latest code (not in Ubuntu yet) then resizing works very well.

[Daniel van Vugt (vanvugt)]

Resizing and stability has been improved a lot today:
https://git.launchpad.net/~xmir-team/xorg-server/+git/xmir/log/

However even when I thought I had re-implemented window resizing correctly, I found the root window does not receive normal resize requests. It works, but it's just more laggy than regular (-rootless) windows.

Not sure when to declare this fixed.

[Daniel van Vugt (vanvugt)]

The original issue is fixed. Resizing now works.

The extra "corruption" issue I added in comment #2 is not a blocking problem and not related to stability either (any more).

[Daniel van Vugt (vanvugt)]

xorg-server (2:1.17.3-2ubuntu2) xenial; urgency=medium