openSUSE Leap 42.1 with latest KDE frameworks/applications from OBS. The "double click" titlebar action in "Window Actions and behavior" is set to Maximize. However, it is ignored in all applications using system titlebars and borders, both KDE and GTK, - double click does nothing. However, double-clicking on Google chrome's titlebar correctly maximizes/unmaximizes its windows as by default Google Chrome does not use "system title bar and borders". rpm -qa | egrep "plasma5|framework|kwin" | sort frameworkintegration-plugin-5.17.0-85.2.x86_64 kwin-4.11.22-1.7.x86_64 kwin5-5.5.2-117.3.x86_64 kwin5-lang-5.5.2-117.3.noarch plasma5-addons-5.5.2-74.2.x86_64 plasma5-addons-kimpanel-5.5.2-74.2.x86_64 plasma5-addons-lang-5.5.2-74.2.noarch plasma5-desktop-5.5.2-128.1.x86_64 plasma5-desktop-branding-openSUSE-13.3-105.2.x86_64 plasma5-desktop-lang-5.5.2-128.1.noarch plasma5-pa-5.5.2-23.2.x86_64 plasma5-pa-lang-5.5.2-23.2.noarch plasma5-pk-updates-0.2-6.2.x86_64 plasma5-session-5.5.2-54.1.noarch plasma5-workspace-5.5.2-158.1.x86_64 plasma5-workspace-branding-openSUSE-13.3-105.2.x86_64 plasma5-workspace-lang-5.5.2-158.1.noarch plasma5-workspace-libs-5.5.2-158.1.x86_64 plasma5-workspace-wallpapers-5.5.2-50.1.noarch plasma-framework-5.17.0-92.2.x86_64 plasma-framework-components-5.17.0-92.2.x86_64 plasma-framework-lang-5.17.0-92.2.noarch plasma-framework-private-5.17.0-92.2.x86_64 Reproducible: Always Steps to Reproduce: 1. Open systemsettings5, make sure the window is not maximized 2. Set the "double click" titlebar action in "Window Actions and behavior" is set to Maximize, click Apply. 3. Double-click on the systemsetting5's titlebar. Actual Results: Nothing. The window gets a bit transparent, each click appears to be treated as a single click and hold (because the mouse cursor changes to the "cross" shape). Expected Results: If the windows was not maximized, then it should be maximized. If the windows is already maximized, then it should be un-maximized.
Something™ screws your timeout to initiate a drag and drop, so you're "too slow" to trigger a double click, because you initiate a drag before releasing the mouse (that's why the window gets translucent) Dolphin-4 is suspected to be the cause of this. *** This bug has been marked as a duplicate of bug 345473 ***
I have not run dolphin-4 even once since the upgrade to Leap.
Might affect dolphin5 as well? run "kcmshell5 mouse", alter the relevant settings on the 2nd tab to something sane (but alter them), apply, see what happens. Run dolphin, open the settings dialog - according to the dupe that was enough to trigger this *shrug*
ok, ran "kcmshell mouse". Double click interval was set to 400msec. Increased to 800msec, clicked Apply. Now double-clicking on titlebars does the expected thing. Set double click interval back to 400msec, clicked Apply. Double-clicking on titlebars still does the expected thing. Win! Ran dolphin5, opened the settings dialog, closed, exited dolphin5 - no effect on double click behavior - still works.
ok, so dolphin5 is good, dolphin4 may be *one* cause, but apparently there're more :-( If it should break again, try to recall what you did just before ;-)