I am sorry if this answer will be a bit longer, but i am a tiny bit
annoyed by the scaling question.
It's not your fault, you don't know how much i get bugged with it,
although it is stated in the readme and i answered it probably a hundred
times in different message boards already, but i will do so again:
It is not just something to consider, to implement or not. jEnesisDS
has a hardware renderer unlike PicodriveDS, Lameboy and also the 0.4a
version of jEnesisDS (which had filtered scaling), which all have a
software renderer.
It is quite easy to scale with a software renderer, because you render
your created framebuffer, basically a bitmap to one of the backgrounds
and then scale it in hardware. Software scaling is really slow. AND all
this cannot easily be done in my hardware renderer. The DS has 4
independant background layers, just 2 of which can be scaled in hardware.
jEnesisDS needs all 4 of them to display the Genesis'backgrounds though,
and they all need to be in the same mode. The only possibility to do
that, is having them all in a text mode, that doesnt allow scaling. As
the graphics are directly converted to DS format, there is also no way
to scale individual elements. Of course it is technically possible, if
you can live with a 1fps emu?
Software rendering is also dead slow. The very optimized ARM asm
software renderer of jEnesisDS 0.4a could do 25-30fps maximum. That was
without sound and Z80 core.
On an average PC emulator, the rendering needs maybe 50-70% of CPU time
of the whole emu.
There are maybe possibilities, which are very complicated and not
obvious, involve using the 3D hardware, screen capturing, doing sprite
tricks to display parts of the backgrounds on them, etc.
Maybe you can understand though, that this is not my top priority
besides eliminating slowdowns, improving the sound, and supporting larger
games.
Anyway. Cheers,
Stephan