Hacking Print on Screen

[PandaOnSmack]

Is it possible to write values on screen through pure assembly?

Would you have to rely on a print function that the game provides? I am just trying to expand my understanding of PPC / Assembly.

 

[Hikari06]

Is it possible to write values on screen through pure assembly?

Would you have to rely on a print function that the game provides? I am just trying to expand my understanding of PPC / Assembly.

I'm not too familiar with the wii u but I guess you could just call the proper functions from your assembly code (OSScreenInit,OSScreenSetBufferEx,OSScreenFlipBuffersEx,OSScreenPutFontEx).

Edit : You could maybe also write the pixels one by one on the screen buffer but I'm not sure what you would gain from doing that.

 

[PandaOnSmack]

Thanks Hikari06. Do you have any examples or how I can call them please? How do you call a function via PPC? ta!

 

[BullyWiiPlaza]

How do you call a function via PPC?

You call a function in assembly by doing a bl to the address of the function (yes, you will have to find that) but I don't think you will get anywhere with this overall since the OSScreen functions won't really work. I tried it before in games and it crashes. Maybe I made a mistake though. In C printing to the screen looks similar to this:

void writeScreen(char message[100], int secondsDelay) {
    OSScreenClearBufferEx(0, 0);
    OSScreenClearBufferEx(1, 0);

    OSScreenPutFontEx(0, 14, 1, message);
    OSScreenPutFontEx(1, 14, 1, message);

    sleep(secondsDelay);

    OSScreenFlipBuffersEx(0);
    OSScreenFlipBuffersEx(1);
}

First of all you have to call OSScreenInit() though to initialize the screen.

I still recommend getting it to work in C first and then maybe try and write it in assembly but if you can use C you may just copy the compiled function's assembly and use that for a code or whatever.

 

[Hikari06]

You call a function in assembly by doing a bl to the address of the function but I don't think you will get anywhere with this overall since the OSScreen functions won't really work. I tried it before in games and it crashes. Maybe I made a mistake though. In C printing to the screen looks similar to this:

void writeScreen(char message[100], int secondsDelay) {
    OSScreenClearBufferEx(0, 0);
    OSScreenClearBufferEx(1, 0);

    OSScreenPutFontEx(0, 14, 1, message);
    OSScreenPutFontEx(1, 14, 1, message);

    sleep(secondsDelay);

    OSScreenFlipBuffersEx(0);
    OSScreenFlipBuffersEx(1);
}

First of all you have to call OSScreenInit() though to initialize the screen.

I still recommend getting it to work in C first and then maybe try and write it in assembly but if you can use C you may just copy the compiled function's assembly and use that for a code or whatever.

The OSScreen functions do work from what I can tell.

Maybe you should add this after OSScreenInit():

int screen_buf0_size = OSScreenGetBufferSizeEx(0);
int screen_buf1_size = OSScreenGetBufferSizeEx(1);
unsigned char *screenBuffer = MEM1_alloc(screen_buf0_size + screen_buf1_size, 0x100);
OSScreenSetBufferEx(0, screenBuffer);
OSScreenSetBufferEx(1, (screenBuffer + screen_buf0_size));

I'm not sure how one would do that directly from assembly though so inspecting the compiled code might be a good idea