Colored lines along the right/bottom edge of screen

[JonyP27]

Hi, I'm new here and I first want to congratulate the developer for this amazing emulator, that allowed me relive some of my childhood gaming experiences.

Now I want to report something that I'm not sure is an emulator bug or API bug, that is when sometimes I run a game in fullscreen mode (within the guest pc) it usually draws a colored lines across the right edge of the screen a sometimes on the bottom, while using the linear filter and forced 4:3 aspect ratio.

It happens most often when running games in 640x480 resolution and less in 800x600, 1024x768 and even in DOS resolution games (usually 320x200). Also it happens when using either OpenGL or Direct3D renderers and not Software or OpenGL 3.0 but I'm most interested in the former renderers as they offer better performance than OpenGL 3.0 and the linear filter that Software doesn't do.

I'm running PCem v15 with a Windows 98 SE guest (Shuttle HOT-557), Mobile Pentium MMX 133, 128Mb RAM, Voodoo 2 SLI, Virge DX and AWE 32. Host is a laptop with an Intel I3 7100u, Geforce 920mx, 8Gb RAM running Windows 10.

Here's a screenshot from Worms 2 that shows these lines:

[leilei]

I think that's the screen texture bleeding in with old texture data from a higher mode. Could probably use a color clear at mode change with a little memcpy (and probably would be useful for implementing backporch colors/margins)

[CryptidWorks]

I've noticed that to but it seems to go away in the majority of full-screen games so I assumed it was just a quirk with the S3 Emulation and never brought it up.

[JonyP27]

Indeed I usually use 800x600 for the desktop but when I changed to 640x480 and ran the game those lines mostly disappeared, though it can still leave a tiny line on the bottom right corner of the screen sometimes, especially when the game shifts between other resolutions while running.
Will have to use that desktop resolution as workaround for now, as it mitigates most of those lines. Thanks for the answers though.