While my previous commit fixes the glitchy y-position when you get stuck
inside a conveyor, I noticed that getting inside a conveyor seems to
always push the player out, despite conveyors sharing the same code with
moving platforms, which has code to temporarily disable their own
collision when the player gets stuck inside them, so that the player
DOESN'T get pushed out.
Well, it turns out that the reason this happens is because conveyors in
a room that get placed during mapclass::loadlevel() get tile 1 placed
underneath them. This is mostly so moving platforms will collide with
them, because otherwise platforms don't collide with other platforms,
and a conveyor is considered a platform.
This means that a conveyor without any tiles behind it will simply get
the player stuck if they get inside it, and the player won't be pushed
out. This is bad, because conveyors don't move, so they'll be stuck
there forever until they press R (or save, quit, and load). This
situation doesn't come up in the main game, but it COULD come up in
custom levels that use the internal createentity() command to create
conveyors that don't have any tiles behind them.
It seems good to fix this as well, while we're at it fixing conveyor
physics, so I'm fixing this as well.
There is this issue with conveyors where if you collide with them, your
intended next y-position doesn't get updated to the position of the
conveyor, and then your y-position gets set to your intended next
y-position. This also applies to horizontally moving platforms.
This bug used to not produce any problems, if at all, until #502 got
merged. Since then, respawning from checkpoints that are on conveyors
would sometimes not update your y-position at all, making it possible to
get stuck inside a death loop that would require you to exit the game
and re-enter it.
But you can always reliably create this bug simply by going into the
editor and placing down a conveyor and checkpoint on top of each other.
Then enter and exit playtesting a bunch of times, and you'll notice the
glitchy y-position Viridian keeps taking on.
The root cause of this is how the game moves the player whenever they
stand on the top or bottom of a conveyor (or a horizontally moving
platform). The game sets their intended next x-position (newxp), then
calls obj.entitymapcollision() on them. This would be okay, except their
intended next y-position (newyp) doesn't get set along with their newxp,
so entitymapcollision() will use the wrong newyp, then find that there
is nothing that will collide with the player at that given newyp, then
update the yp of the player to the wrong newyp.
So, the platform logic simply doesn't set the player's newyp. Why does
the player have the wrong newyp? It's because moving platforms (and
conveyors) are updated first before all other entities are, and this
includes the code that checks the player for collisions with moving
platforms. That's right: the moving platform collision code gets ran
before the player properly gets updated. This means that the game will
use the newyp of the previous frame, which could be anything, really,
but it most likely just means the intended next y-position of the player
gets canceled, leaving the player with the same y-position they had
before.
Okay, but this bug only seems to happen when you put a checkpoint inside
a conveyor (or a moving platform that hasn't started moving yet) and
start playtesting from it, so why doesn't this bug happen more often,
then? Well, it's probably because of luck and coincidence. Most of the
time, if you're colliding with a conveyor or horizontally moving
platform, you probably have a correct newyp from the previous frame of
the game, so there'd be no problems. And before #502 got merged, this
previous frame would be provided by the player having to fall to the
surface due to the y-offset of their savepoint. However, if you make it
so that you immediately teleport on to a conveyor (because you died),
then this bug will rear its ugly head.
I got this warning during compilation because there were two nested for
loops both defining i. Better to have different names to make sure some
compilers won't overwrite the outer variable with the inner one.
I was investigating a desync in my Nova TAS, and it turns out that
the gravity line collision functions check for the `oldxp` and `oldyp`
of the player, i.e. their position on the previous frame, along with
their position on the current frame. So, if the player either collided
with the gravity line last frame or this frame, then the player collided
with the gravity line this frame.
Except, that's not actually true. It turns out that `oldxp` and `oldyp`
don't necessarily always correspond to the `xp` and `yp` of the player
on the previous frame. It turns out that your `oldyp` will be updated if
you stand on a vertically moving platform, before the gravity line
collision function gets ran. So, if you were colliding with a gravity
line on the previous frame, but you got moved out of there by a
vertically moving platform, then you just don't collide with the gravity
line at all.
However, this behavior changed in 2.3 after my over-30-FPS patch got
merged (#220). That patch took advantage of the existing `oldxp` and
`oldyp` entity attributes, and uses them to interpolate their positions
during rendering to make everything look real smooth.
Previously, `oldxp` and `oldyp` would both be updated in
`entityclass::updateentitylogic()`. However, I moved it in that patch to
update right before `gameinput()` in `main.cpp`.
As a result, `oldyp` no longer gets updated whenever the player stands
on a vertically moving platform. This ends up desyncing my TAS.
As expected, updating `oldyp` in `entityclass::movingplatformfix()` (the
function responsible for moving the player whenever they stand on a
vertically moving platform) makes it so that my TAS syncs, but the
visuals are glitchy when standing on a vertically moving platform. And
as much as I'd like to get rid of gravity lines checking for whether
you've collided with them on the previous frame, doing that desyncs my
TAS, too.
In the end, it seems like I should just leave `oldxp` and `oldyp` alone,
and switch to using dedicated variables that are never used in the
physics of the game. So I'm introducing `lerpoldxp` and `lerpoldyp`, and
replacing all instances of using `oldxp` and `oldyp` that my over-30-FPS
patch added, with `lerpoldxp` and `lerpoldyp` instead.
After doing this, and applying #503 as well, my Nova TAS syncs after
some minor but acceptable fixes with Viridian's walkingframe.
This commit restores the evaluation order of moving platforms and conveyors to
be what it was in 2.2. The evaluation order changed in 2.3 after the patchset
to improve the handling of the `obj.entities` and `obj.blocks` vectors (#191).
By evaluation order, I'm talking about the order in which platforms and
conveyors will be evaluated (and thus will take priority) if Viridian stands
on both a conveyor or platform at once, and they either have different speeds
or are pointing in different directions. Nowhere in the main game is there a
place where you can stand on two different conveyors/platforms at once, so
this is solely within the territory of custom levels, which is my specialty.
So what caused this evaluation order to change? Well, every moving platform
and conveyor in the game is actually made up of two objects: an entity, and a
block. The entity is the part that moves around, and the block is the part
that actually has the collision.
But if the entity is the part that moves around, and entities and blocks are
in entirely separate vectors, how is the block part going to move along with
it? Well, maybe you'd guess some sort of unique ID system, but spend some time
digging around the code and you won't find any trace of any (there's no
attribute on an entity to store such an ID, for starters).
Instead, what the game does is actually remove all blocks that coincide with
the exact top-left corner of the entity, and then create a new one. Destroying
and creating blocks like this all the time is hugely wasteful, but hey, it
worked.
So why did the evaluation order change in 2.3? Well, to understand that,
you'll need to understand 2.2's `active` system. Instead of having an object
be real simply by virtue of it existing, 2.2 had this system where the object
was only real if it had its `active` attribute set to true. In other words,
you would be looking at a fake object that didn't actually exist if its
`active` attribute was false.
On the surface, this doesn't seem that bad. But this can lead to "holes" in a
given vector of objects. A hole is simply an inactive object neighbored by
active objects (or the inactive object could be the first one in the vector,
but then have an active object immediately following it).
If you have a vector of 3 objects, all of them active, then removing the
second one will result in the vector containing an active object, followed by
an inactive object, followed by an active one. However, since the switch to
more properly use vectors instead of relying on this `active` system, there's
no longer any way for holes to exist in a vector. Properly removing an object
from a vector will just shift the rest of the objects down, so if we remove
the second object after the vector fix, then this will simply move the third
object into the slot of where the second object used to be.
So, what happens if you destroy a block and then create a new one in the
`active` system? Let's say that your `obj.blocks` looks like this, and here
I'm denoting each block by writing out its coordinates:
[30,60] [70,90] [80,100]
and that you want to update the position of the second one, because the entity
that that blocks belongs to has been updated. Okay, so, you delete that block,
which then makes things look like this:
[30,60] [-] [80,100]
and then afterwards, you create a new block with the updated position,
resulting in this:
[30,60] [74,90] [80,100]
Since `entityclass::createblock()` will find the first block slot that has a
false `active` attribute, it puts the new object in the same slot as the old
one. What has been essentially done here is that the slot of the block has
basically been reserved for the new block with the new position. Here, the
evaluation order of each block will stay the same.
But then 2.3 comes along and changes things up. So we start with an
`obj.blocks` like this again:
[30,60] [70,90] [80,100]
and we want to update the second block, like before. So we remove the second
block, resulting in this:
[30,60] [80,100]
It should be obvious that unlike before, where the third block stayed in the
third slot, the third block has now been moved to the second slot. But
continuing on; we are now going to create the new block with its updated
position, resulting in this:
[30,60] [80,100] [70,90]
At this point, we can see that the evaluation order of these blocks has been
changed due to the fact that the third block has now been moved to the slot
that was previously the slot of the second block.
So what can we do about this? Well, we can basically emulate what VVVVVV did
in 2.2, which is disable a block without actually removing it - except I'm not
going to reintroduce an `active` attribute or anything. I'll disable the
collision of all blocks at a certain position by setting their widths and
heights to 0, and then re-enable them later by finding the first block at that
same position, updating its position, and re-assigning its width and height
again.
The former is what `entityclass::nocollisionat()` does; the latter is what
`entityclass::moveblockto()` does. The former mimicks turning off the `active`
attribute of all blocks sharing a certain top-left corner; the latter mimicks
creating a new block - and it will only do this for one block, because
`entityclass::createblock()` in 2.2 only looked for the first block with a
false `active` attribute.
Now, some quirks relied on the previous behavior of destroying and creating
blocks, but all of these quirks have been preserved with the way I implemented
this fix.
The first quirk is that platforms passing through 0,0 will destroy all spike
hitboxes, script boxes, activity zones, and one-way hitboxes in the room. The
hitboxes of moving platforms, disappearing platforms, 1x1 quicksand, and
conveyors will not be affected.
This is a consequence of the fact that the former group uses the `x` and `y`
of their `rect`, while the latter group uses the `xp` and `yp` attributes. So
the `xp` and `yp` of the former are both 0. Meaning, a platform passing
through 0,0 destroys them all.
Having these separate coordinates seems like an artifact from the Flash days.
(And furthermore, there's an unused `x` and `y` attribute on all blocks,
making for technically three separate sets of coordinates! This should
probably be cleaned up, except for what I'm about to say...) But actually, if
you merge both sets of coordinates into one, this lets moving platforms
destroy script boxes and activity zones if it passes through the top-left
corner of them, which is probably far worse than the destruction being
localized to a specific coordinate that would never likely be reached
normally.
This quirk is preserved just fine without any special-casing, because instead
of destroying all blocks at 0,0, they just get disabled, which does the same
job. This quirk seems trivial to fix if I made it so that the position of a
platform's block was updated instantaneously instead of having one step to
disable it and another step to re-enable it, but I aim to preserve as much
quirks as possible.
The second quirk is that a moving platform passing through the top-left corner
of a disappearing platform or 1x1 quicksand will destroy the block of that
disappearing platform. This is because, again, when a moving platform updates,
it destroys all blocks at its previous position, not just only one block. This
is automatically preserved because this commit just disables the block of the
disappearing platform instead of removing it. Just like the last one, this
quirk seems extremely trivial to fix, and this time by simply making it so
`entityclass::nocollisionat()` would have a `break` statement, i.e. only
disabling the first block it finds instead of all blocks it finds, but I want
to keep all quirks that are possible to keep.
The last quirk is that, apparently, in order to prevent pushing the player
vertically out of a moving platform if they get inside of one, the game
destroys the block of the moving platform. If I had missed this edge case,
then the block would've been destroyed, leaving the moving platform with no
collision. But I caught it in my testing, so the block gets disabled instead
of destroyed. Also, it seems obtuse for those who don't understand why a
platform's block gets destroyed or disabled whenever the player collides with
it in `entityclass::collisioncheck()`, so I've put up a comment documenting it
as well.
The different platform evaluation order desyncs my Nova TAS, but after
applying this patchset and #504, my TAS syncs fine (save for the different
walkingframe from starting immediately on the ground instead of in the air
(#502), but that's minor and can be easily fixed).
I've attached a test level to the pull request for this commit (#503) to
demonstrate that this patchset not only fixes platform evaluation order, but
preserves some bugs and quirks with the existing block system.
The first room demonstrates the fixed platform evaluation order, by stepping
on the conveyors that both point into each other. In 2.2, Viridian will move
to the right of the background pillar, but in 2.3, Viridian will move to the
left of the pillar. However, after applying this patch, Viridian will now move
to the right of the pillar once again.
The second room demonstrates that the platform-passing-through-0,0 trick still
works (as explained above).
The last room demonstrates that platforms passing through the top-left corners
of disappearing platforms or 1x1 quicksand will remove the blocks of those
entities, causing Viridian to immediately pass through them. This trick is
still preserved after my patchset is applied.
Previously, setting the actual volume of the music was all over the
place. Which isn't bad, but when I added being able to press N to mute
the music specifically, I should've made it so that there would be a
volume variable somewhere that the game looks at if the music is
unmuted, and otherwise sets the actual volume to 0 if the game is muted.
This resulted in things like #400 and #505 and having to add a bunch of
special-cased checks like game.musicmuted and game.completestop. But
instead of adding a bunch of special-case code, just make it so there's
a central place where Mix_VolumeMusic() actually gets called, and if
some piece of code wants to set the music volume, they can set
music.musicVolume. But the music handling logic in main.cpp gets the
final say on whether to listen to music.musicVolume, or to mute the game
entirely.
This is how the music handling code should have been from the start
(when pressing N to mute the music was added).
Fixes#505.
The value of the macro might not change in the future, but it's there
for a reason. That reason being to improve code readability, because
otherwise 128 would just be a magic number that plopped in out of
nowhere. Sometimes the game uses MIX_MAX_VOLUME, other times it uses
128, so to be consistent I'm just going to enforce MIX_MAX_VOLUME
entirely.
This reverts commit cf5ad166e3.
My implementation will make it so single-case patches like this commit
won't be necessary anymore (there's no need to add a special-case check
for game.musicmuted, the way that I'm gonna do it). In fact, it's better
if I just revert the commit entirely.
It seems like the start point of a custom level and all checkpoints in
the game end up putting your spawn point one pixel away from the surface
it touches, which seems like an oversight. I'm going to enforce some
consistency here and make it so that all spawn points, whenever you
start from a start point or a checkpoint, will always be correctly
positioned flush with the surface they're standing on, and not one pixel
more or less than that.
An exotic checkpoint is a checkpoint with a sprite that is neither the
flipped checkpoint nor unflipped checkpoint. More specifically, it's a
checkpoint whose edentity p1 attribute is something other than 0 or 1.
Normally, whenever you touch an exotic checkpoint in-game, your
savepoint's y-position and gravitycontrol don't get touched. However, in
the editor, spawning from an exotic checkpoint means that your
gravitycontrol gets set to a value that is neither 0 nor 1. In this
invalid gravitycontrol state, Viridian is treated like they're flipped,
but they cannot unflip.
This is an inconsistency between the editor and in-game, so I'm fixing
it. Now, spawning from an exotic checkpoint in the editor will just set
your gravitycontrol to 0, i.e. unflipped.
So, 77a636509b fixed the fact that you
only got 1 frame of onground/onroof when standing on a vertical moving
platform, but removing those lines entirely means that it takes 1 frame
before the onground/onroof of 2 actually takes effect. This desyncs my
Nova TAS, so it seems important to fix.
The onroof/onground attributes are used to determine if the player is
standing on a surface and is eligible to flip. Most notably, it is an
integer and not a boolean, and it starts at 2, giving the player 2
frames to edge-flip, i.e. they can still flip 2 frames after walking off
an edge.
However, these attributes are unnecessarily reassigned in
movingplatformfix() (which is the function that deals exclusively with
vertically-moving platforms; horizontal moving platforms get their own
hormovingplatformfix()). Whoever wrote this misunderstood what
onroof/onground meant; they thought that they were booleans, and so set
them to true, instead of the proper value of 2. This ends up setting
onroof/onground to 1 instead of 2, causing a discrepancy with vertical
moving platforms and the rest of the surfaces in the game.
The bigger mistake here is duplicating code that never needed to be
duplicated. The onroof/onground assignment in gamelogic() works
perfectly fine for vertical moving platforms. Indeed, after testing it
with libTAS, I can confirm that removing the duplicate assignments
restores being able to edge-flip off of moving platforms with 2 frames
of leeway, instead of only 1 frame. It also doesn't change how long it
takes for the onroof/onground to get set when the player is recognized
as standing on a vertically-moving platform, either.
And so, it's better to not duplicate this code, because when you
duplicate it you run the risk of making a mistake, as I just
demonstrated.
By "unnecessary qualifiers to self", I mean something like using the
'game.' qualifier for a variable on the Game class when you're inside a
function on the Game class itself. This patch is to enforce consistency
as most of the code doesn't have these unnecessary qualifiers.
To prevent further unnecessary qualifiers to self, I made it so the
extern in each header file can be omitted by using a define. That way,
if someone writes something referring to 'game.' on a Game function,
there will be a compile error.
However, if you really need to have a reference to the global name, and
you're within the same .cpp file as the implementation of that object,
you can just do the extern at the function-level. A good example of this
is editorinput()/editorrender()/editorlogic() in editor.cpp. In my
opinion, they should probably be split off into their own separate file
because editor.cpp is getting way too big, but this will do for now.
This is a refactor that simply moves all temporary variables off of
entityclass, and makes it so they are no longer global variables. This
makes the resulting code easier to understand as it is less entangled
with global state.
These attributes were:
- colpoint1
- colpoint2
- tempx
- tempy
- tempw
- temph
- temp
- temp2
- tpx1
- tpy1
- tpx2
- tpy2
- temprect
- temprect2
- x (actually unused)
- dx
- dy
- dr
- px
- py
- linetemp
- activetrigger
- skipblocks
- skipdirblocks
Most of these attributes were assigned before any of the times they were
used, so it's easy to prove that ungloballing them won't change any
behaviors. However, dx, dy, dr, and skipblocks are a bit more tricky to
analyze. They relate to blocks, with dx, dy, and dr more specifically
relating to one-way tiles. So after some testing with the quirks of
one-way tiles, it seems that the jankiness of one-way tiles haven't
changed at all, either.
Unfortunately, the attribute k is clearly used without being assigned
beforehand, so I can't move it off of entityclass. It's the same story
with the attribute k that Graphics has, too.
This prevents users from being confused whenever they type a pipe in the
script editor, then save the level and load it again and see their
script lines unexpectedly splitting in two. Now if you attempt to type a
pipe, it simply won't happen at all.
Fixes#379.
It's possible that SDL_atoi() could call the libc atoi(), and if a
string is provided that's too large to fit into an integer, then that
would result in undefined behavior. To avoid this, use SDL_strtol()
instead.
Instead of copying to a temporary string, just use SDL_strncmp(). Also,
I checked the blame, and apparently I committed the line that used
strcmp() instead of SDL_strcmp(), for whatever reason. But that's fixed
now.
For some reason, the variable `k` is on entityclass and gets mutated in
createentity() and createblock(). Then updateentities() uses it without
checking if it's valid, because either `k` or the size of `entities`
could have changed in the meantime. To fix any potential undefined
behavior, these bounds checks should be added.
This fixes a bug where font_positions wouldn't get cleared after exiting
a custom level that had a font.txt if it didn't exist in the default
graphics, leading to messed-up-looking font rendering.
This bug was originally discovered by Ally.
You're intended to rescue Violet first, and not second, third, or
fourth, and especially not last.
If you rescue her second, third, or fourth, your crewmate progress will
be reset, but you won't be able to re-rescue them again. This is because
Vitellary, Verdigris, Victoria, and Vermilion will be temporarily marked
as rescued during the `bigopenworld` cutscene, so duplicate versions of
them don't spawn during the cutscene, and then will be marked as missing
later to undo it.
This first issue can be trivially fixed by simply toggling flags to
prevent duplicates of them from spawning during the cutscene instead of
fiddling with their rescue statuses.
However, there is still another issue. If you rescue Violet last, then
you won't be warped to the Final Level, meaning you can't properly
complete the game. This can be fixed by adding a `crewrescued() == 6`
check to the Space Station 1 Level Complete cutscene. There is
additionally a temporary unrescuing of Violet so she doesn't get
duplicated during the `bigopenworld` cutscene, and I've had to move that
to the start of the `bigopenworld` and `bigopenworldskip` scripts,
otherwise the `crewrescued() == 6` check won't work properly.
I haven't added hooks for Intermission 1 or 2 because you're not really
meant to play the intermissions with Violet (but you probably could
anyway, there'd just be no dialogue).
Oh, and the pre-Final Level cutscene expects the player to already be
hidden before it starts playing, but if you rescue Violet last the
player is still visible, so I've fixed that. But there still ends up
being two Violets, so I'll probably replace it with a special cutscene
later that's not so nonsensical.
I have no idea why neither conveyors and moving and disappearing
platforms rendered in the editor or in-game use
Graphics::drawentcolours(), but this needs to be bounds-checked just as
I did for the in-game rendering function.
The entity getters I'm referring to are entityclass::getscm(),
entityclass::getlineat(), entityclass::getcrewman(), and
entityclass::getcustomcrewman().
Even though the player should always exist, and the player should always
be indice 0, I wouldn't want to make that assumption. I've been wrong
before.
Also, these functions returning 0 lull you into a false sense of
security. If you assume that commands using these functions are fine,
you'll forget about the fact that `i` in those commands could be
potentially anything, given an invalid argument. In fact, it's possible
to index createactivityzone(), flipgravity(), and customposition()
out-of-bounds by setting `i` to anything! Well, WAS possible. I fixed it
so now they can't.
Furthermore, in the game.scmmoveme block in gamelogic(), obj.getplayer()
wasn't even checked, even though it's been checked in all other places.
I only caught it just now because I wanted to bounds-check all usages of
obj.getscm(), too, and that game.scmmove block also used obj.getscm()
without bounds-checking it as well.
When this is done, there is potential for a mistake to occur when
writing out the bounds check, which is eliminated when using the macro
instead. Luckily, this doesn't seem to have happened, but what's even
worse is I hardcoded 400 instead of using SDL_arraysize(ed.level), so if
the size of ed.level the bounds checks would all be wrong, which
wouldn't be good. But that's fixed now, too.
This is because if they are manually written out, they are more likely
to contain mistakes.
In fact, after further review, there are several functions with
incorrect manually-written bounds checks:
* entityclass::entitycollide()
* entityclass::removeentity()
* entityclass::removeblock()
* entityclass::copylinecross()
* entityclass::revertlinecross()
All of those functions forgot to do 'greater than or equal to' instead
of 'greater than' when comparing against the size of the vector. So they
were erroneous. But they are now fixed.
It's better to do INBOUNDS_VEC(i, obj.entities) instead of 'i > -1'.
'i > -1' is used in cases like obj.getplayer(), which COULD return a
sentinel value of -1 and so correct code will have to check that value.
However, I am now of the opinion that INBOUNDS_VEC() should be used and
isn't unnecessary.
Consider the case of the face() script command: it's not enough to check
i > -1, you should read the routine carefully. Because if you look
closely, you'll see that it's not guaranteed that 'i' will be initialized
at all in that command. Indeed, if you call face() with invalid
arguments, it won't be. And so, 'i' could be something like 215, and
that would index out-of-bounds, and that wouldn't be good. Therefore,
it's better to have the full bounds check instead of checking only one
bounds. Many commands are like this, after some searching I can also
name position(), changemood(), changetile(), changegravity(), etc.
It also makes the code more explicit. Now you don't have to wonder what
-1 means or why it's being checked, you can just read the 'INBOUNDS' and
go "oh, that checks if it's actually inbounds or not".
For some reason it called obj.getplayer() and did nothing with the
result. Weird. But it does say "Test script for space station" above.
Removing this fixes an 'unused variable' warning.
With the scope of these variables reduced, it makes analyzing this
function easier, as you can now clearly see all temporary variables are
actually initialized before they're used.
Since there's an INBOUNDS_ARR() macro, it's much better to specify the
macro for the vector is a macro for the vector, to avoid confusion.
All usages of this macro have been renamed accordingly.
Stuck prevention (pushing the player/supercrewmate out if they are
inside a wall) has been factored out into its own function, so it's no
longer copy-pasted but slightly tweaked just for the supercrewmate.
Instead of having two separate functions to move entities along vertical
moving platforms, one for the player and one for the supercrewmate, they
have been consolidated into one function.
In-level, they were made to be gray in #323. The editor does not reflect this however; they're still shown as
green. For the same reasons in #323, this adds special cases to draw the entities as gray.
Closes#372.
Also, I changed my name in contributors.txt to be my username as I didn't feel comfortable with it being my name.
Co-authored-by: Misa <ness.of.onett.earthbound@gmail.com>
The game has four different functions for the same XML schema:
Game::loadtele(), Game::savetele(), Game::loadquick(), and
Game::savequick(). This essentially means one XML schema has been
copy-pasted three different times.
I can at least trim that number down to being copy-pasted only one time
by de-duplicating the reading and writing part. So both Game::loadtele()
and Game::loadquick() now use Game::readmaingamesave(), and
Game::savetele() and Game::savequick() now use
Game::writemaingamesave().
This will make it take less work to add XML forwards compatibility
(#373).
