[d3d9] Change correctness factor to 0.5f

[Blisto91]

Been doing a lot of testing of this issue to figure out what is up and down.

The original issue the current code fixed is actually a game bug that also happens with the version of the FF13Fix addon used back then (1.4.6). On Windows with native d3d9 amd drivers this issue can be observed when running the game with a 2560 x 1440 resolution.
This was then later fixed in the addon and so if you download the latest version of FF13Fix it will look correct both with the native driver and dxvk with a 0.5f correctness factor. https://github.com/rebtd7/FF13Fix/releases

Fixed misaligned screen effects (proper fix for the 1440p resolution)

Fixing the game bug back then in dxvk sadly introduced issues in other games like #3708, #3818 and #4425.

I have tested on radv, amdvlk open , amd pro, nvk and Nvidia prop that a correctness factor of specifically 0.5f fixes those issues. FFXIV will behave like on Windows and the addon can still be used to fix the 1440p bug.
(amdvlk and amd pro didn't want to work with gamescope when faking 1440p)

Fixes #3708
Fixes #3818
Fixes #4425
Closes #4461

[Blisto91]

Some of the issues linked were not correct at first, whoops. Should be now.

Also adding #4461 as this seems to reduce to the issue back to native levels so it isn't worse with dxvk.

[pchome]

Could you please check 2048x864?
It's 2560x1080 variant.
Many, many, mAnY bugs here and there with 21:9 (~) resolution.
(~ because it's 2.37037037037 not 2.33333333333)

[Blisto91]

What more specifically do you want me to recheck? The only one i had to fake my resolution for to reproduce is FF XIII (my monitor is 1080p not 1440p) since we didn't have the apitrace at hand anymore so i had to check the game itself.

Edit: actually i had to make a GTA IV trace too but that reproduced fine without gamescope.

[pchome]

Just to make sure it's ok not just for 1080p or 720, 1440 ...
There is smaller variant for 21:9 (~) 1536x648.
Whatever gamescope or wine virtual desktop.

[Blisto91]

I checked GTA 4, Final Fantasy XIII and Train Simulator with radv and Nvidias driver at 2048x864 and didn't notice any issues. UNDER NIGHT IN-BIRTH II only supports a pre set standard list of resolutions it seems.
Also note that i gather in the Train Simulator issue that they use some third party payed for weather pack which i don't have so just checked the vanilla game. I can't replay apitraces back at arbitrary resolutions as in windowed mode they will be at the size they were captured and trying to run them in fullscreen mode causes a crash in apitrace.

[pchome]

I checked GTA 4, Final Fantasy XIII and Train Simulator with radv and Nvidias driver at 2048x864 and didn't notice any issues. UNDER NIGHT IN-BIRTH II only supports a pre set standard list of resolutions it seems.

thanks