performance rendering e.g. PolyText8 is unusably slow
This issue might be related to #943 , although it is not solely happening on AMD hardware. I am able to observe it on nVidia and Intel GPU hardware on a wide span of OSes (Ubuntu 14 all the way up to recent, CentOS7, Fedora 29-33).
In the linked ticket #943 TkGate is used to demonstrate the issue, but I am having the issue even more severly using Cadence Simvision Schematic Tracer, which is a professional EDA hardware development debug tool. It also uses 2D commands to render its schematics and is super snappy when being used via VNC or Xephyr embedded X-Server. So anytime the 'original' X-server running on the desktop/laptop system just gets a pixmap from VNC or Xephyr, everything is fine. But once X2Go Remote client or SSH -X is used or the application is run locally, the schematic tracer becomes unusable, although it is usually super snappy to use. And I mean unusable, rendering a small schematic can take up to 25 seconds, which usually renders in just a few ms.
But there is one funny detail: It only happens when text is rendered, not the lines. If I zoom out far enough, there is no issue, because no text is rendered:
I then used xscope for tracing and some of the last stuff I see when it starts to hang is this:
So my main question is: what to do about this? The good news is: there are cases where it is working as described above, so I hope there is some trickery available to tell X to render this application differently. Of course the best thing would be if this would be fixed.
But are there some magic X11-Settings, env variables, alternatives libraries etc. that I could try to circumvent this problem? We currently help ourselves by redirecting simvision into a Xephyr instance but this comes with other problems like clipboard issues, ugly fonts and does not work with X2Go. Really what we need is a way to either configure our systems (Fedora 33 at present) in a way to render this application differently or a fix of glamor (where I expect the issue) is needed to really address this in X11.