Window flickering problem in XWin multiwindow mode
Sat Apr 30 15:25:24 GMT 2022
On 26/04/2022 04:53, S.J. Luo wrote:
> I have some EDA tools running on a Linux machine and display on my Windows
> PC using xorg-server-21.1.3 XWin multiwindow mode
> Sometimes the application window flickers forever for an unknown reason.
> The problem became more severe after my PC upgrade to Windows10.
> Googling the problem, I did not find such issue reported.
> I decided to take advantage of open source nature and solve it by myself.
> After re-compiling and debugging, I found a calling loop triggered.
> Here I eliminate the detail of the cause. I may write later if someone requires.
> Knowing the root cause, I am now able to demonstrate the issue with a small
> test case as well as a patch that works for me. Both are attached below.
Thanks very much for taking the time to look into this, and writing a patch.
I will apply it.
But I'd like to add a bit more commentary, which perhaps you can supply,
about the analysis you did to determine:
1. how the code is misbehaving
2. how this change remedies that
3. how this change doesn't effect anything else
What your fix does is examine the queue of pending WM messages to
determine if there are any more pending for the window receiving a
WM_WM_CHANGE_STATE message, and if there are, ignore it.
It seems to me that is error prone, in a couple of ways:
1. it should check the message type as well, as e.g. a pending message
of a different type could cause a WM_WM_CHANGE_STATE message to be ignored.
2. even then, assuming that successive WM_WM_CHANGE_STATE messages
cancel out each other isn't always true e.g. consider a sequence of
_NET_WM_STATE_ADD _NET_WM_STATE_MAXIMIZED_VERT followed by
If you were to send other patches in future, please send them as
attachments, or even better, using git format-patch/git send-email, as
that makes it much easier to apply them without white-space damage and
with correct attribution.
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