nesdev.com

So... Scroll position cannot be read by looking at some address of CPU or PPU RAM?
Also, your note about when to read the registers, you're talking about $2000 and $2001? I think I'm reading it when the emulator is paused, the same moment any memview file prompt popup is launched. So far with my tests it seems to be working ok, but it could be that it's loading at some random moment and I'm lucky. I'm just using default memview behavior, it seems to be fine.

Moving on:

I'm having a really hard time understanding the code. I've only found two instances of the string "2005" on ppu.cpp.


I don't know what to make of this. What is "A200x"?

Also, when programming a game in ca65 I've learned horizontal scroll has two important values: the selected nametable, as defined by the two least significant bits of PPUCTRL register, and a value of 0-255 to be written to $2005 that defines the pixel position of the scroll relative to the selected nametable. Is that equivalent to what I'm looking for in the source code? I ask this because the wiki talks about fine and coarse scroll values, which is confusing me. Source: http://wiki.nesdev.com/w/index.php/PPU_scrolling



It took me a long time to understand this. So the PPU has a register called "x". So... I need registers v and x?

ppu.cpp has this function, but I don't understand how it's used

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B2005 is defined here

No, scroll isn't just stored in RAM anywhere, it's an internal PPU thing and intimately tied up with the PPU address (written through $2006) as well. That wiki page you linked should explain, hopefully.

My C++ knowledge is too limited. It's too abstract to me right now. DECLFW is defined as "void x (uint32 A, uint8 V)" in fceu.h. I have no idea what that means. Shouldn't A be the accumulator, therefore uint8?

Anyway, B2005 only seems to be ever used to initialize PPU, so that doesn't seem to be useful. I tried to retrieve PPUGenLatch and it always came out as 0. I don't know how to access ppu.cpp's "V" from memview.cpp even though I've included ppu.h. I can't include ppu.cpp, it gives a random error elsewhere.

There's this, but I don't know how to access those vars from memview.cpp. I tried searching for how savestate does it, but I couldn't either. I think I'm going to give up for now.

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A is for "address" and V is for "value", in that function.

Though I think really you found a better interface already in ppu_getScroll, which already seems designed to convert the current register state into convenient pixel scroll coordinates.



Edit: made a typo in the code.

40 minutes after reading your message, I think I got it. At least looking at the output file binary seems to be producing numbers different than zero. It was giving me an error about const params and pointers I assume (from my error research), though I don't fully understood it. So after trying some things semi blindly, this is what worked:



Thanks you very much, importing dumps is getting very robust, at least for games that don't change much graphics mid-frame.

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Sorry, I made a typo above. There should not have been an & in front of x and y.

You don't need to make a pointer to a reference and then dereference them like you're doing, you can just use the two ints directly. The & in the function's declaration automatically references them and makes them available for output.