I prefer to use double-clicking to open folder and files. However, I notice that changing this setting in Dolphin changes how many other applications behave. It shoudn't. I have recently filed a bug report for KInfoCenter. (https://bugs.kde.org/show_bug.cgi?id=326291) Today, I've noticed that the same setting affects how the KDE Help Center behaves. It exactly the same issue as in KInfoCenter. I can select items in the tree view but main view is not updated accordingly. Thinking that this is not an issue related to a specific application but a general design issue, I decided to file this report for the KDE itself. According the KInfoCenter bug report, developers connect to the activated() signal instead of clicked(). Reproducible: Always Steps to Reproduce: 1. Change the Navigation setting in Dolphin to use double-clicking. 2. Open KInfoCenter or KDE Help Center. 3. Try to change the main view by selecting items in the tree view at the left by single-clicking. Actual Results: Items get selected but the relevant content not shown in the main view. Expected Results: Update the main view after single-clicking an item in the tree view.
It's not a design issue. Applications can automatically follow the user setting for activating view items using the activated() signal. If they do not want to follow the setting, but enforce single or double-click, then they connect to clicked() or doubleClicked() signals.
(In reply to comment #1) > It's not a design issue. Applications can automatically follow the user > setting for activating view items using the activated() signal. If they do > not want to follow the setting, but enforce single or double-click, then > they connect to clicked() or doubleClicked() signals. Isn't it assuming too much that a setting about folder/file viewing in Dolphin is taken into account in other applications and used for showing content not related to files or folders?
The setting affects all "item views", e.g. the System Settings main view, and any other view where the application developer thinks it presents its items in a way that "double click spoiled" users would instinctively use a double click. Here, that may not be case, so it could be changed to force a single click.
Further clarification: the setting is actually system wide, see System Settings > Input Devices > Mouse > General tab. Dolphin duplicates this setting, because users where confused that there was no option to change it.
https://docs.kde.org/trunk5/en/applications/dolphin/configuring-dolphin.html#preferences-dialog: The option to open items with a single or double mouse click is a system wide setting and can be changed in the System Settings in the Input Devices → Mouse module.