Non-standard mouse button setup yields incorrect behavior
(Text is copied from a posting I made earlier in the Support forum.)
I'm attempting to use OpenMW V0.43.0 on Windows 7 64-bit. I have the English Steam version of Morrowind and do not have this issue in the Steam game. I do have some mods installed but have not activated them in OpenMW (data files unchecked). The problem happens consistently.
I use the mouse with my left hand, and I use a non-standard setup for the mouse buttons. The (physical) right button is my primary button and the (physical) left button is my secondary button. I have this setup configured in Windows Control Panel Mouse settings: "Switch primary and secondary buttons".
In the OpenMW GUI, I configure the right button ("Mouse 1") for "Use" and the left button ("Mouse 3) for "Inventory". However, in the game, the buttons operate improperly. The first click of the right button does nothing; the second click triggers "Inventory". And the left button triggers "Use". That is, the operations are the opposite of how I've configured them (with the additional quirk that I must click the right button twice to get a response).
If I uncheck the Windows setting "Switch primary and secondary buttons" (i.e., use the standard Windows mouse button setup) I can then get the in-game settings and interactions I want: the right button triggers "Use" and the left button triggers "Inventory". However, I can no longer click any buttons in the inventory/stats/magic/map windows. If I click on a button with the right button, nothing happens. If I click with the left button, it exits menu mode and returns me to the game.
In summary, mouse buttons operate properly in OpenMW only if I (1) use the standard Windows mouse button setup (i.e., "Switch primary and secondary buttons" is ) and (2) use the right button for "Use" and the left button for "Inventory". Any other combination of settings yields incorrect in-game mouse button behavior.
I can't reproduce this with the equivalent OS setting on Linux. I flip the OS setting and then the game will invert the buttons properly and out of the box. This leads me to believe the bug may be only in the Windows SDL backend not inverting the buttons as it should.