Many thanks to http://bytepointer.com/tasm/index.htm for providing a
better searchable resource for TASM's default `LEA imm16` → `MOV imm16`
optimization, which we initially had to hack around here.
Funded by -Tom-.
So apparently, this way of distorting a circle into an ellipse (?) by
adding a value to the angle for one of the two coordinates isn't
actually widely known in math and doesn't have a name. Fair enough.
Funded by -Tom-.
Sure, I like me some global variables too. If you have to temporarily
replace them for a single function call though, it's pretty much the
textbook example of where *not* to use them.
Funded by -Tom-.
Yup, nothing interesting in here.
Except for maybe the confirmation that LS00.BB is used for the curved
bullets used by Shinki and EX-Alice?
Funded by -Tom-.
… because TH04's version of this takes the ASCII stage ID directly from
the resident structure.
So boss battles are simply triggered by setting the background tile
scroll speed to 0? That means…
Funded by zorg.
Again, one of these functions that ZUN *probably* wrote in ASM for shits
and giggles, which you *again could* "decompile" using in-line assembly,
but that kind of defeats the point.
Oh well, at least the fact that the parameter is passed in AL means that
the calling convention must have been __fastcall, and *that* part *does*
cleanly map to C. Unlike some of the functions in d08a7f4.
Funded by zorg.
Struct strLASER in uth05win… except that the member names in that one
were not only a bit too unclear, but `ageThres` and `shootAgeThres`
should have also been the other way round.
Also, yes, TH04's laser structure seems completely different.
Funded by -Tom-.
With TH05 definitely being the Galaxy Brain version of this function.
You'll see once I get to push the C decompilation for that one…
Anyway, that covers all shared input functions of TH02-TH05!
Funded by zorg.
Seemingly included in every other larger structure describing anything
remotely sprite-like. Couldn't find this in the earlier games,
unfortunately…
Funded by zorg.
TH02 just seems to use a sequence of branches in sub_D6CA.
I thought about keeping variable and function names consistent with
uth05win (on which most upcoming reverse-engineering commits will be
based). But as it will turn out, it ignored a certain very important
substructure, so I don't think it's worth introducing this naming style
clash.
Funded by zorg.
Yes, you're reading that correctly. If the cursor is at 255, reading a
16-bit value will fill the upper 8 bits with the neighboring cursor
value, which always is 0xFF.
Funded by -Tom-.
Oh, right, these functions can have parameters. So, let's turn snd_kaja_func()
into a macro that combines the function number and the parameter into the AX
value for the driver.
And renaming them all to the short filenames they will be decompiled to for
consistency. These functions aren't really immediately hardware-related, as
we've established earlier in the decompilation.
Yes, all of it. Including the bouncing polygons, of course. And since it's
placed at the end of ZUN's code inside the executable, the code's already
position-independent and fully hackable.
Also covering the two variations for blitting only every second row or
blitting only a 320x200 quarter, as seen in the endings.
So yeah, there's indeed nothing wrong with piread.cpp. TH03 just uses that
separate function that only blits every second row of an image, and indeed
always loads the entire image as it would appear in a PNG conversion. Here's
what happens if you display these images using the non-interlacing function:
https://www.dropbox.com/s/885krj09d9l0890/th03%20PI%20no%20interlace.png
With TH03 changing the calling convention for most of the code from __cdecl to
__pascal, I've been getting more and more confused about this myself. So,
let's settle on the following consistent syntax for function calls:
* C where the calling convention is actually __cdecl and where TASM's emitted
__cdecl code matches the original binary
* PASCAL where the calling convention is actually __pascal
* STDCALL where the calling convention is actually __cdecl, but where
the caller either defers stack cleanup (summing up the stack size of
multiple functions, then cleaning it all in a single "add sp" instruction)
or where the stack is cleared in a different way (e.g. "pop cx").
Unfortunately though, when using the ARG directive to automatically generate
an appropriate RET instruction for the given calling convention, TASM always
emits ENTER and LEAVE instructions even when no local variables are declared,
which greatly limits the number of functions where we can use that syntax. -.-
Well, the naming.
Even though only TH02 actually uses MIDI (and thus, the MMD driver), every
game since then contains interrupt instructions for both functions. We could
just name it "pmd", since it seems like that's what came first - the AH
numbers of the 6 functions that make up MMD's interrupt API are identical to
those of the equivalent functions in PMD, even including gaps in the numbering
for PMD functions that don't have an equivalent in MIDI. However, except for
the FM sound effect handling and the key display in TH05's Music Room, these 6
functions are all the games actually use. Also, we already distinguish between
PMD and MMD in the driver check functions, and it might be confusing to only
imply PMD from now on?
So, "kaja" it is, collectively referring to the shared aspects of both
drivers.
Yup, packfiles finally proved that we really have a different set of changes
to master.lib in every game. Also, there are bound to be more of these game-
specific small changes to otherwise identical code in ZUN's own code.
And hey, no need to define that value in the build scripts anymore.
(I've also considered just copying modified versions into the individual game
subdirectories, but it's not too nice to expect people to diff them in order
to actually understand why these copies exist and where the changes actually
are.)
nmlgc
