Amiga v2600 is a port of Alex Hornby's Atari VCS2600 emulator done by Matthew Stroup. Ie, I didn't write it, I have only modified others code.
See the Amiga v2600 home page for further information.
The modifications to the GUI has been included in Matthew's 0.82 release of Amiga v2600. Using the emulator on a screen of it's own still fails in 0.82 however, so the modifications to the display may be useful for those of you running Picasso96.
Matthew added a gadtools GUI to the emulator which did a nice job. However, it only used the font Topaz8 which is quite tiny on my Workbench. I modified amiga_gui.c to make the GUI font sensitive and by default use the screen font.
The window opened by v2600 for the GUI was of the type GimmieZeroZero. This kind of window is easy to use, but a bit slower than a normal window. With the new layout code for the GUI this wasn't needed anymore and v2600 now open a regular window.
The custom screen mode use direct manipulation of the screens BitMap when doing a chunky to planar conversion. This is a major no-no when running on a graphics card. So why not use the window mode? Well, if you want that authentic blocky feeling a lowres screen is the way to go!
I'm using a Spectrum card with my A3000 and use the Picasso96 software for retargeting graphics. By using direct calls to the Picasso96 API it is possible to lock the BitMap of a Screen for rendering into it. The format of the BitMap can be chunky, so a direct copy of the emulator's rendering buffer is possible.
With my patches a 8-bitplane chunky screen is opened vith p96OpenScreenTags() and it's bitmap is later used as target for when displaying the buffer. It's neither fast nor fancy, but it does the job and avoids potential crashes.
My replacement amiga_disp.c is heavily modifed for Picasso96 and will not be useful on other systems. I even went so far as to remove support for ECS/AGA screens.