10.x -> 11 changes in compositing behavior

[Ken Moore]

On 03/27/2015 13:57, Ken Moore wrote:
> Greetings!
>
> I am noticing a strange inconsistency between the behavior of windows 
> that have manual compositing redirect enabled between FreeBSD 10 and 
> 11 systems. Basically, FreeBSD 10 is properly saving the window image 
> on the X11 server for use later without any issues, but on FreeBSD 11 
> all that is getting saved is a transparent/blank image. The image *is* 
> there (kind of), since I can probe it and see the sizing and other 
> properties, but the image itself is blank.
>
> Is there anything that has changed on FreeBSD 11 with regards to 
> when/how images are saved to the server?
> I have posted my general procedure below, would you recommend 
> something different?
>
> Thanks!
>
>
> ---- Additional Details ----
>
> I am actually running into this with the Lumina Desktop system tray 
> functionality, so let me give you a quick overview of how that is 
> arranged, later on I will list a quick "pseudo-code" for you to 
> reproduce this.
>
> Note: This is the general "embedding" procedure for a system tray icon
> 1) Reparent the tray window into the container window.
> 2) Set the "manual" compositing redirect on the tray window (having it 
> save it's image to the X11 server/stack, but not paint the image on 
> the window - resulting in a transparent overlay)
> 3) Have the container grab the tray window image from the stack, and 
> overlay/paint that image onto of itself (fixing issues with 
> transparency on systems not using a compositing window manager)
>
> This results in the image actually being painted on the container, 
> while the tray window is a transparent "layer" above the container to 
> directly receive all the input/interaction events. This results in it 
> responding quickly and without a lot of overhead/redirection of all 
> the various kinds of input events.
>
> If I simply comment out the manual compositing redirect (or set it to 
> automatic), the tray icon/image shows up just find but has a black 
> background where the image is transparent (it is not showing the 
> parent/container image underneath), so I have narrowed it down to that 
> one setting which is causing the problem but am kind of at a loss as 
> to how to fix/bypass it.
>
>
> --------  Relevant Information ------
> First off, the versions of xorg that I am comparing are identical 
> between the two systems:
> xorg 7.7_1
> xorg-apps 7.7_2
> xorg-docs 1.7,1
> xorg-drivers 7.7_2
> xorg_server 1.14.7_2,1
>
> My two systems:
> 1 - bare-metal) FreeBSD 10.1-RELEASE-p17 (Actually PC-BSD 10.1.1, up 
> to date with latest from freebsd-update and packages)
> 2 - VirtualBox VM) FreeBSD 11.0-CURRENTMAR2015 (PC-BSD March image for 
> FreeBSD 11, created Mar 1, ~2PM EST)
>  (although identical behavior has been found on the February image for 
> FreeBSD-Current as well, installed on either bare-metal or in a VM)
>
>
>
> ----- Steps to Reproduce -----
> I am going to list both XCB and XLib commands that were used to 
> replicate this behaviour below. The XCB/XLib usage was consistant and 
> they were not "mixed" within an application.
>
> -- General idea/usage for replicating the effect --
> 1) Set manual compositing redirect on a window to have it save it's 
> image on the stack but without painting it on the window itself.
>   xcb_composite_redirect_window(connection, window, 
> XCB_COMPOSITE_REDIRECT_MANUAL);
>   XCompositeRedirectWindow(display, window, CompositeRedirectManual);
>
> 2) Grab the image for the window from the stack at some later time
>   xcb_image_get()
>   XGetImage()
>
> 3) Paint the image so it can be viewed (I do it on a separate window)
>

  So I found a work-around, not sure where the problem was exactly, but 
using the Qt method for grabbing an image from a window 
(QScreen->grabWindow()) seems to work fine on FreeBSD 11 (even with the 
manual composite redirection set) whereas directly fetching the image 
through XCB/XLib was not. Perhaps it has better fallback/alternate routines?

Sorry for the noise!

-- 
~~ Ken Moore ~~
PC-BSD/iXsystems