[Core Port Req.] Flycast - Sega Dreamcast

Making an updated version over #856 with information.

Upstream info

• Target platforms: win/mac/tux
• Source repo
• Language(s): C++ & C (libretro API)
• License: GNU GPLv2

Originally based on reicast, before things happened. :)

Merits

Probably one of the biggest things it has going for it-- besides Dreamcast games is that it has slowly improved on its NAOMI support, and can be a reason to hide out the MAME support we have as that has worse performance on NAOMI titles.

It also has RetroAchievements and Custom Textures (probably less of a requirement to get on first deployment, even though as showcased by Mupen there is a demand).

And it supports a variety of controller types such as Keyboard (The Typing of the Dead), Mouse (Quake III Arena), Light-Gun Twin Sticks, and the ASCII Mission Stick.

Technical details

For the renderer backends it features; OpenGL, Vulkan, Direct 3D 9/11.

Many of the settings it has can probably be tucked away in a "users don't need to touch this" such as setting Transparent Sorting to Per Pixel by default, and then figuring out what to do with CPU Mode as even though Interpreter is much more accurate, it's much more taxing (also having overclocking inaccessible).

Displaying the VMU might be a nice touch, as Flycast does it by default either ontop of the game, or off to the side (in full screen).

Obviously people would still like their goodizers especially if it helps for them setting up certain tricks if it makes it easier to see what they're doing, but also being able to disable Fog for instance if there's tricks that require basically "flying blind" depending on the game.

Start with the linked Flycast source repository and its libretro API boundary, then compare the requested Windows, macOS, and Linux targets with BizHawk's existing core-port approach. Done means a decided integration scope and a working Flycast core with the relevant renderer, controller, and configuration requirements addressed; this issue does not name files or tests.