Homebrew Would a screenshot taking homebrew/hack work?

[Hiccup]

Would it be possible to make homebrew that patches the game somehow (like action replay, for example) , to inject code that saves a screenshot to the flashcard's SD card when a button or button combo is pressed?

Or an application (homebrew or PC) that patches a ROM so that it contains code that saves a screenshot to the flashcard's SD card when a button or button combo is pressed?

Or have I got the wrong idea about how these things work?

 

[DanTheManMS]

Unfortunately no, this is not something that is possible with just a homebrew program. With the way the DS works, you cannot run two programs at the same time; each DS binary takes complete control over the entire DS unit and all its hardware, clearing out any program that was otherwise running in the background. Multitasking on a system with merely 4 MB of RAM is simply not feasible outside of DSLinux. Even if it was possible, you would only be able to take a screenshot of the "main" screen, whichever one the game itself defines; not both screens at once.

The only way to accomplish this would be via a special command that would only work for a specific flash cart. I remember the CycloDS team was working on this sort of thing at one point but they eventually gave up due to the technical limitations involved.

Your best bet is to just run the game in an emulator on your computer and grab your screenshots that way. Unless you want to try creating a Jumbotron DS that is, heh...

EDIT: For what it's worth, you absolutely have the right idea. One would think that it's possible. It's a shame that it isn't.

 

[migles]

there is no homebrew for that... and as user above me said it should be really hard to make one
(and i find it hard to believe that it's impossible or that hard, the DSTWO can put the game on pause and open is own menu, and it can even do cheat and use save slots (which is basically dumping the whole ram into a file, so i believe there is a way even with limitations to take screenshots...)

however, when i was playing phoenix wright and wanted to take screenshots, i saved the game, took out the sd card, opened it on emulator, took the screenshot and back playing to DS
this is a too much work process but it works when trying to screenshot something specific on some games...

 

[FAST6191]

What the others have said and emulation is great these days, indeed it has been for a while. However if you really must then you could probably reconstruct a screen* if you can manage to do a savestate of the game like some flash carts can do, there are some issues with some aspects of the VRAM and 3d not being visible in memory (some parts are write only) but it should still be possible.
Point a gun at my head and give me a month and I might be able to get a commercial game or two to have enough of a DLDI library to tell it to dump memory somewhere, I might also be able to abuse a GBA slot flash cart, GBA flash cart SRAM or indeed even a DS game's save memory if there is enough of it to also funnel a dump of the VRAM or something. However I would sooner make a screen capture device or just use an emulator.

*you could rebuild the VRAM in a somewhat cut down manner (you could even mod some things, think https://gbatemp.net/threads/resize-sprites.295053/#post-3681859 but gone large) or you could try to get the savestate running in an emulator.

 

[Hiccup]

Thanks for the responces.
I understand the DS is not capabable of running a comercial game alongside another piece of software, such as homebrew.
I was more thinking along the lines of what FAST6191 is saying. I.e. getting a ROM software you want a screenshot of (e.g. a comercial game), and modifying it , either permenantly or temporarily and either on the DS or on a PC, to make it capable of capturing itself in some way, and running the ROM on a standard slot-1 flash card, without the processers that the supercard dstwo has.