Support windowed fullscreen

We should allow usage of the SDL_WINDOW_FULLSCREEN_DESKTOP flag instead of SDL_WINDOW_FULLSCREEN. This allows borderless window fullscreen over exclusive fullscreen.

Difference is described here https://wiki.libsdl.org/SDL_SetWindowFullscreen

To not mess with existing settings I propose we add another setting on top of fullscreen.

fullscreen = true
borderless fullscreen = true

In our settings managers, we can change the fullscreen checkbox (both in-game and launcher) to a dropdown with three options:

1. Fullscreen
2. Borderless Fullscreen
3. Windowed

changed the description

We possibly want to just implicitly enable this when the selected resolution matches the resolution for the selected monitor, we're in windowed mode, and the window border is disabled.

added Feature label

I'm a bit against having two settings as one of the setting has no effect if the other is off, I would go with a single setting called "window mode" which is can be "fullscreen", "fullscreen borderless", "window" which is also less confusing to the end user. We could always import the current fullscreen variable and omit it the next time its saved.

Yeah I think best bet is to have a window mode with the 3 options and deprecate existing fullscreen and windowed setting. After all it's how basically every game has these settings, so no need to deviate from an established standard.

We probably don't want to remove the obsolete setting from the config file, by the way. We don't have to change it any more, but it's a pain for people switching revisions (e.g. testing regressions) if the newer ones remove settings the old ones still use.

No need to remove it, no. Though I have seen plenty of people's settings.cfg with full Ogre settings

I somehow ended up with a whole copy of settings-default.cfg from the OGRE3D era in my settings.cfg, so I'm guessing one of our old releases initialised the user config with the default settings and we changed that so it wouldn't cause problems if we changed the defaults.

If the old setting is not omitted once the new setting is in-effect it would keep re-importing the fullscreen one, I don't think it would be possible to keep it this way. The alternative is to keep two variables but in the UI we consider it a single state, but that adds a bit more code again.

I don't understand what you mean. If we have a new setting we simply won't use the old ones anymore.

You mean to just entirely ignore the old "fullscreen" then? My idea was to use the last set value to set the new one at first launch, that would break if we were to keep the old one in this case.

Yes ignore it, you would lose the last used preference, but that's not a big deal. Easy to change back from in game menu or launcher.

mentioned in merge request !1825 (merged)

changed title from Support borderless fullscreen to Support windowed fullscreen

mentioned in commit 0145819b

closed with merge request !1825 (merged)

changed milestone to %openmw-0.48