Add scanlines in scandouble rotate

[shaeon]

It would be great to add a scanline effect to the rotate screen. Is it possible to add it?

I checked the code and saw that the scanlines parameter doesn't exist in the rotate module.

Thanks for your support.

[gyurco]

Probably it can be added, however it's not guaranteed that every 2nd line is the duplicate of every 1st line, so there's a chance it'll look weird in some cases.
@robinsonb5 what do you think?

[robinsonb5]

Firstly, scanlines on a portrait format arcade machine would have been vertical, not horizontal: the screen was scanning parallel to the long edge, just like a regular monitor.

Because rotation also involves scaling, and that scaling is fractional, attempting to render accurate scanlines would look awful, because the scaling would partially filter them out.

Scanlines could be faked by adding them after scaling - and this would be pretty easy. They'd be at the wrong pitch compared with a real machine, however (and the end result would probably look awful on a VGA screen unless the user is able to adjust the pixel clock just right - but it might look OK on HDMI.)

[gyurco]

It's a good point that original-like scanlines would be vertical.