So, when you use OpenGL scaling it upscales the image using a nearest-neighbor algorithm, so you get a nice, crisp version of the original image versus what happens when an image is upscaled using a bilinear algorithm, where it ends up looking like you're viewing it through a glass of water; all blurry, hard to look at for more than a few minutes without getting a headache (so it amazes me that some people prefer it this way).
The problem is that ScummVM changed the way it handles the image scaling, at least in the current SVN builds I use. It used to be that all you had to do was set "openGL_nearest" in the filters option. But now they've split the functionality into two settings. You need to set "opengl" as the filter but you also need to set "vga" under the "render_mode" setting. D-Fend Reloaded 1.4.4 currently appends the render mode setting as "render-mode" to the commandline rather than, say, adding the line "render_mode=vga" under the [scummvm] heading in the ini file. If you right-click one of your scummvm games and choose to view the config file you can see how D-Fend lays it all out, and right now it's borked; adding "render-mode=whatever" to the commandline of scummvm does squat and that's all D-Fend is able to do currently, probably because that's how it worked in older scummvm versions.
As to your second question, there's a setting in D-Fend that allows you to point to where your ScummVM install is located. If you want you can store a folder named "ScummVM" within your D-Fend Reloaded folder and use relative paths so that it always knows to find it there.
I'm using ScummVM version 18.104.22.168. I've played around with this a bit, and I think I've got it to work, at least with this build.
If you right-click the game, go to "ScummVM settings" and in the Custom settings box, add this:
It should work. I added updates_check=0 because every time I launched the game (after adding the other two parameters), it kept asking me about how often I wanted to update. I am not sure why it asks me in this scenario, versus when I have nothing in the Custom settings box. Though I might add, I got opengl_nearest to work without setting the render mode to VGA. I just let it stay as "default" and it seemed to work exactly the same. Is there any reason in particular why I shouldn't let render mode stay as default if it seems to work otherwise (when using opengl_nearest)?
In your opinion, is it preferable to play ScummVM games with the OpenGL (no filtering) option? Is that the only mode that gives you that crisp image that you're talking about?
Another question - when using opengl_nearest, is there any way to increase the size of the ScummVM window upon launch? I noticed that you can click and drag the window to make it whatever size you want, but I'd prefer to have it automatically be larger when I launch the game so I don't have to manually resize it and try to get it just right so black borders aren't showing.