It adds a border to Flashback, but it is not how the game should look - the result is that you don't see the whole picture.

I was afraid of something like that. It means that the game sets non-zero border color but it still black and carries no useful load. Two possible solutions: detect complete (or nearly complete) black and ignore it as well OR set no border as DOSBox default because it is only needed by a handful of games. In ideal case, shortcut key -- I just did not want to touch that part of the code until the feature gets debugged and proven.

If it is "normal", double-check that it is patched correctly -- it is the only scaler that has implementation without PMAKE/XMAKE, and that implementation must be disabled and replaced in order for overscan to work.

I didn't touch anything related to normal (none) part in render_templates.h.
I just added some lines into hq2x part for HQ2x scaler to use overscan.
[EDIT]
In fullscreen mode, I found that hq2x & openglhq support overscan.
But the border is black.

About border appearing when not needed:
- robertmo: Should have saw that coming (but didn't)... Good catch!
- If you have blending enabled and set the thickness to be small, it shouldn't be too distracting (I'd hope)
- Could just make it disabled by default and add a note to the docs about how to turn it on for games that need it, but then you might be missing out if you don't know that a game you're playing uses that feature
- A hotkey is probably the best solution, as vasyl suggested. This would make it feasable to have overscan border emulation enabled by default because it would be easy for the user to toggle off when it's too distracting or not needed
- I think detecting "near-black" is probably a suboptimal approach, as some games may actually have a use for black border color. Also, some games may set useless border colors that are nowhere close to black. I spent a few minutes trying to come up with other fancy ways of detecting useless borders, but couldn't think of anything that is likely to work. Doesn't mean there isn't a slick way I haven't thought of though...

Well what I find is that I set it to size of "1" so that it doesn't distract me in Crystal Caves while still being useful for alerting me to finish the level. Howevr I did notice the effect doesn't like surface, but overlay works like a charm.

Since I use d-fend it is off in every other game, so I wouldn't have noticed if it happens in anything else besides flashback 😦

I just noticed: The border is always unblended black in fullscreen when using "surface" output mode. Most likely because of a switch to 8bit paletted mode rather than my regular 32bit desktop.

Precisely. I've uploaded an update to my patch which uses opaque borders if destination bpp is 8. Better than nothing but far from perfect. Is there any way to force fullscreen mode to use 16 or 32 bit surface in current build?
There are other possible solutions:
a) attempt to find the nearest color (slow, may break badly in some cases);
b) show border on every other frame (probably too ugly);
c) use stippled border ("poor man blending").
I will play with those solutions a little more and post my findings.

EDIT: (b) is unacceptable -- it gets too distracting, especially with frameskip. Both (a) and (c) work, (c) is very reliable, (a) is not so but some people may prefer it. I've updated the patch so it supports both (a) and (c). It does try to find the nearest palette entry if "overscanstrength" is 1 to 9. For 10 it will do simple stipple. Crystal Caves work best with 2, although stipple effect is not bad. Well, get the patch and let me know what you think.
Now, the other unresolved item is keyboard shortcut. Any suggestions which key combination should I use?

well I'm not very fond of another keyboard shortcut for something so little used.

I was thinking of the following
If you do fullfixed you get a black area around your screen if it's smaller then your fullfixed resolution
The colour of that area is actually changable. ( I know because when implementing it was red to help us determine/improve the centering code) Can't the border use that area ? (colour wise ?)
It's more like a real pc then.

Excellent idea. I did not think about it because I never use that mode. It should be easy to implement, I will do it in the next iteration.
So, if we don't use keyboard shortcuts we just leave it as option in dosbox.conf so it will be up to frontends, right?

Quick comment, just in case if anybody tries it.
This patch is incompatible with scaler optimization patch by Kronuz (see separate thread). Don't even try merging them, there are too just too many conflicts. The optimization patch definitely has the priority at this point and it is in active development. I will update this overscan patch after the dust settles in optimizations.

Hey, what exactly does the overscan do? it just adds borders to the games? did some games have borders? (I can't remember this overscan thing)

vasyl wrote:

Quick comment, just in case if anybody tries it.
This patch is incompatible with scaler optimization patch by Kronuz (see separate thread). Don't even try merging them, there are too just too many conflicts. The optimization patch definitely has the priority at this point and it is in active development. I will update this overscan patch after the dust settles in optimizations.

@vasyl: At this point it should be easy to add the overscan support to the optimized code. I've tried to keep my patch really simple and clean but yet fast, and though it was a difficult thing to do I think it's readable; you should check the latest (I think it's easier to read). It's probably just a matter of changing the CA to CI defines (probably)

That's the part of VGA display around the image. In most cases it stayed black but some games actually changed color. There were a couple cases when games used this feature to enhance the actual gameplay. DOSBox does not have any area around the image (except in certain fullscreen modes), modern LCDs don't have overscan either. So, this patch just blends overscan color into the image edge using a few different algorithms. It's more like proof of concept than a feature, the implementation is rather hacked (scalers are the easiest place to put this code it but not the most logical place). The patch is low priority and does not have much chances to get into CVS any time soon (if ever) so don't worry too much about it. As I said, I will wait for you to finalize your changes, get them to CVS, and then I will update this one.

hey, maybe dosbox could implement virtual configuration knobs for the virtual display. That way you could screw around with the display just like on a real old monitor, and resize the visible portion (and consequently, the border) to your heart's content. Could also have a handy factory reset like you could never have on the real thing. Should be no problem for output modes such as direct3d and opengl. That would be gold... 😉

Edit: I was kidding.. though it could add a cool nostalgic feel, so I'd probably actually respect someone for implementing it so long as they didn't mess up the code. If someone were to actually try and do this, I suppose the OSD (on-screen display) style of new monitors would probably be the way to go, due to interface issues (no knob input devices available).

Edit 2: I'm on an LCD and always run at 1280x1024 in fullscreen. I disabled aspect correction for added speed and see aspect problems all the time. Considering the confusion and/or inconsistency between output modes, fullfixed, fullscreen vs windowed, scalers, hw scaling, and low-res upscaling by lcd's and/or display drivers (that most people don't even initially know is occurring), most lcd users haven't got a handle on it.. and human intervention in the end may have another use anyway.

Caverns of Kroz 2 shows a red border in the intro screen where you pick if your a Novice, Experienced or, Advanced player.

Yep, I rule for finding another game that does this.

So far that's about 4 games that have a border. Sigh. I really don't want to go through 600 games in NTVDM flippin' between full/Window screen. Especially since 2003 NTVDM takes forever to switch from full-screen to windowed.

So time to narrow it down:

I think we can safely say that no protected mode games probably use a border....although I'm sure someone could if they wanted to.

Can the same thing be said about VGA games as well?

Since I'm currently going through my games identifying all CGA games then it would be a pretty simple matter to test all of those....once I get 'em all identified that is.

I wouldn't assume anything if I was trying to make a comprehensive list (is that what you're talking about?)

But I'd start by testing lots of text, CGA, EGA and VGA shareware games from the Apogee era (epecially Apogee and Epic games). There could even be SVGA games that do it for all I know - it's been a long time since I've played any of the Moraff games, for example.

The patch is not compatible with the most recent CVS and cannot be easily repaired. I will see what can be done but only after SVGA patch gets fixed -- that one takes obvious priority. Stay tuned.

Just coming in late...

Why cant you default to having it off and detect if the game changes the color of the border, if it does, then turn it on.

So in the conf file you set all the normal settings of the border (blend amount ect...) but there is no switch for on\off, it just turns on when needed.

I'm not sure how it's currently implemented, but I like that idea.

Latest list of games with a border:

Castle of Kroz
Caverns of Kroz
Caverns of Kroz 2
Commander Keen 1
Commander Keen 2
Commander Keen 3
Commander Keen 4
Crystal Caves
Dungeons of Kroz
Dungeons of Kroz 2
Final Crusade of Kroz
IBM Alley cat (CGA)
Kingdom of Kroz
Kingdom of Kroz 2
Lost Adventures of Kroz
Return to Kroz
Secret Agent
Temple of Kroz

18 games. Muahahahaha.

At least one of the Catacombs series of games uses the border. It changes colour whenever you are attacked, which is useful when you are hit from behind and can't see the monster.