Created attachment 124051 [details] Annotated screenshot depicting of the problem KWin + Plasma from git master, LibreOffice 6.3.3.2.0+ (latest released version) STEPS TO REPRODUCE 1. Use an Icons-Only Task Manager 2. Use the Large Icons task Switcher with the "Only One window per application" setting checked 2. Open LibreOffice Writer 3. Open LibreOffice Calc 4. Hit Alt+Tab OBSERVED RESULT In the Task Switcher, Writer and Calc are represented as multiple windows of the same app and are grouped into a single entry, with an icon and title determined by which window is highest on the stacking order. This creates a discrepancy between what the Task Manager shows and what the Task Switcher shows. See attached screenshot. EXPECTED RESULT The Task Switcher should represent the windows as distinct apps rather than multiple windows of the same app, just like the Task Switcher does. ADDITIONAL INFORMATION *technically* they are in fact multiple windows of the same app due to the design of the LibreOffice apps. The soffice.bin process spawns a window, then dynamically changes its WM_CLASS string, or something like that. I am not 100% sure of the technical details, but I do recall that the Task Manager needed to implement some special code to handle it; see https://cgit.kde.org/plasma-workspace.git/commit/?id=b15eaf38b6bf8d5af7fdc0caff05679a063819cf.
KWin thinks that Writer and Calc belong to the same application because they are in the same window group and also have the same pid. So it's logical to present only one item in the task switcher.
(In reply to Vlad Zahorodnii from comment #1) > KWin thinks that Writer and Calc belong to the same application because they > are in the same window group and also have the same pid. So it's logical to > present only one item in the task switcher. It's not logical to present the same data differently between the Task Switcher and the Task Manager. The fact that these tao apps are in the same window group and also have the same pid are implementation details; from a user perspective, they are different apps. The Task manager manages to figure this out; if the Task Switcher does not, then we have a buggy behavior of the same thing being presented differently in different contexts. I know this situation is non-ideal because it amounts to working around an odd app behavior, but sometimes that's what you need to do to ensure internal consistency and a good user experience.
Alternatively, is there something simple that the LibreOffice apps can do to signal to KWin that they want to be considered separate apps? I don't think it's likely that the devs will reconsider their current approach of using the same process for all apps (requires total re-architecture of everything), but is there a way they can hint to the window manager that windows belonging to different LibreOffice apps want to be considered different apps?
(In reply to Nate Graham from comment #2) > It's not logical to present the same data differently between the Task > Switcher and the Task Manager. The fact that these tao apps are in the same > window group and also have the same pid are implementation details; from a > user perspective, they are different apps. The Task manager manages to > figure this out; if the Task Switcher does not, then we have a buggy > behavior of the same thing being presented differently in different contexts. Well, I don't deny the fact that the current behavior is counter-intuitive when it comes to switching between LibreOffice windows. The task manager doesn't have such problems because it checks only the app id. On the other hand, KWin has more sophisticated heuristics to verify that the given two clients belong to the same application. The only way to fix this problem is to make sure that we check the window class first. Although, frankly, I don't know what impact it will have on the rest of KWin. We use AbstractClient::belongToSameApplication() quite a lot in core code. Changing any of its details may have serious consequences.