Switching between multiple tabs in Konsole happens with a noticeable delay. Reproducible: Always Steps to Reproduce: 1. Open Konsole with a few tabs. 2. Try switching between the tabs by pressing Shift+Left/Shift+Right or with mouse. 3. See how fast the actual switching happens. Actual Results: In my case there is noticeable delay between the key is pressed and the tab is actually switched (I guess about 200-500 ms). Expected Results: The tab should switch immediately. Kubuntu 16.04 x86_64, Nvidia drivers 364.19. I don't have this problem with Yakuake on the same machine. Other applications (KDE or not) with tabs also don't exhibit delays when switching tabs.
I should add that the console input is not delayed - the keypresses are immediately shown in the console. Browsing the main menu and tabs in Konsole settings are also not affected.
Another way to see the slow interface update is to try minimizing and restoring Konsole window. When the window is restored, you can see part of the underlying desktop for about 500 ms before the Konsole window contents appear.
I stopped using Konsole and switched to Terminator because of this problem. The delay is just unbearable with my normal work. After some usage I can say that Terminator also seem to render console contents faster. I used to think that the delay is related to ssh connection speed (I often used Konsole for remote connections via ssh) but Terminator does seem to work much faster in the very same conditions.
I've upgraded to Kubuntu 16.10 and the problem is still there. What's worse is that 16.10 ships yakuake 3.0.2, which is now based on KDE Framework 5 and exhibits the same problem. The additional problem with yakuake is that its animation is extremely slow and loads CPU (probably, 1 thread 100%). 16.04 shipped yakuake 2.9.9, which was based on KDE4, and it didn't have this problem. Yakuake is crucial for my workflow and cannot be as easily replaced as konsole. Because the problem is the same in both applications, I assume the problem is in some common component that comes with KDE5. I'm reassigning it to kpart for now, feel free to update to a more appropriate component, if needed. I'm also raising the priority because console functionality is essential and as it is it is unusable. I'll also add that the problem does not manifest itself on my other machine with Intel drivers (it has Kubuntu 16.10 as well). Please, fix this or advise a workaround. Let me know if I can help fixing it.
(In reply to Lastique from comment #1) > I should add that the console input is not delayed - the keypresses are > immediately shown in the console. That is not actually true. After having compared the experience between Terminator and Konsole/Yakuake based on KDEF5, I can certainly see that the latter renders much slower and the delay is visible.
I think I found the problem on my system. I installed fontconfig-infinality packages at some point in the past. The packages replaced libfontconfig6 and provided better quality of rendered fonts. It worked fine with KDE4, but apparently caused huge performance drop with KDE5 konsole/yakuake. I've downgraded to libfontconfig6 from the distro and performance seems normal now.
Thanks for your thorough investigation! As you found out, the problem apparently lied within fontconfig-infinality and not within Konsole. If the bug does still exist, consider reporting this behavior to the developers of fontconfig-infinanlity. Thanks!