This is sometimes an issue with older games that are designed to run in an 'exclusive' fullscreen mode. The first thing I would note is that Oath in Felghana supports two different APIs for rendering: Direct3D 8 and Direct3D 9. For some reason, GOG defaults to setting up a shortcut that launches the Direct3D 8 version of the game. However, you can run the Direct3D 9 version by navigating to the game's folder and running the "ysf_win_dx9" application. You'll probably want to run the Direct3D 9 version anway, since it's the newer API of the two and somewhat more likely to (still) be well supported by newer GPU drivers.
Do note that the game also has two separate configuration utilities. One is named "config.exe" which is for configuring the Direct3D 8 version of the game, and the other is named "config_dx9.exe", which is for configuring the Direct3D 9 version. So, if you want to play around with the game's low-level settings, be sure to run the right one! Neither of these configuration utilities has an option to control whether the fullscreen mode is exclusive or borderless. However, they both allow for the game's resolution to be set. You may find it beneficial to ensure that the resolution is set to your desktop's native resolution. Why might that matter? Well, by default the game runs at a resolution of 640x480. Ideally, a modern GPU will try to upscale lower resolutions to the native resolution of your display in such a case. However, that is sometimes dependent on the GPU drivers you are using and the options that you have chosen for it. In the worst case, trying to run a game at 640x480 might result in your monitor being asked to switch resolutions, which is really not a good thing for LCD monitors.
Now, if none of that helps, you'll probably want to consider the use of a Direct3D wrapper. A wrapper is simply an implementation of a component - in this case, Direct3D - that is able to translate the draw calls to a different version of Direct3D, or even to something else altogether (such as Vulkan). Or, to put it another way, it acts as a proxy. Some of these wrappers can try to force the game to be run in what's known as a borderless window. That doesn't mean that the game has to be run in a desktop window per se; the borderless window can overlay the desktop and be visually indistinguishable from the fullscreen exclusive mode. The point of interest is that borderless window modes are intrinsically Alt+Tab friendly. If you'd like to give that a try, I would suggest playing around with dgVoodoo2. I posted some information about it in the thread titled "Ys 1 - full screen convo not appearing". Basically, it's capable of translating draw calls from earlier versions of Direct3D (including 9) to Direct3D 11, and it supports a number of interesting configuration options, including the ability to force a "borderless" rendering mode and to perform high-quality upscaling of lower resolutions to the native desktop resolution.
There is also DXVK, which can translate Direct3D 9 to Vulkan. By design, DXVK tries to render the game in a borderless fullscreen mode, even without the tweaking of any of its options.
Post edited September 13, 2024 by ZXPlectrum
