I have button icons, the buttons themselves function as expected, and the camera doesn't stutter whatsoever, even when rotating it as quickly as possible on the spot. If you can think of another problem I should have, then by all means, I'm all ears.
Ok, 20 minutes doing more testing XD For a second, I've achieved the game doesn't work with the controller even with the mod
Please, I ask you to do some simple tests. It will take a minute.
Go to the control options -> controller, and make sure you have disabled the "Always show controller indicators" option (maybe the translation is different). Disabling it allows the UI to jump between mouse/keyboard and controller buttons whatever you touch them.
Then go to the options menu and click on the triggers to change the tab, notice if there is a flicker in the button indicators by jumping between keyboard keys and control buttons.
Another test is, in the controls tab, in the keyboard section, focus on one of the actions, walking forward for example. Press Enter on your keyboard to redefine that action, and then press the BACK button on your controller. Is any button / key assigned? In my case, in the scenario where the controller works without the mod, I can see the Tab key assigned even when xbox controller config is disabled in steam.
I want to note that browsing the profiles for controllers in Steam for Prey, the recommended is the Arkane official xbox 360 controller profile. If Prey has native xinput controller support (and this includes the 360 controller), why has Arkane created an official profile precisely for that controller?
To be sure Steam is not messing with the implementation of the controller in a game, you need to do more than enabling/disabling that function in the steam parameters menu. You have to:
Go to steam parameters and ENABLE xbox / ps4
Enter in Picture mode, go to Prey section, Manage Game and Controller configuration and then disable the
Use steam configuration for non-steam controllers
It seems that this option sometimes is enabled by default, it overrides the controller config you have in steam general parameters, and is not visible/changeable if you don't enable the general controller support in steam. That's the reason I can have controller controls in the game, with controller UI (because Prey has a "always show controller UI" option) but is not perfectly smooth, because is not native.
After that, disable the xbox/ps4 controller support in steam parameters.