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This patch restores some 2.2 behavior, fixing a regression caused by the refactor of properly using std::vectors. In 2.2, the game allocated 200 items in obj.entities, but used a system where each entity had an `active` attribute to signify if the entity actually existed or not. When dealing with entities, you would have to check this `active` flag, or else you'd be dealing with an entity that didn't actually exist. (By the way, what I'm saying applies to blocks and obj.blocks as well, except for some small differing details like the game allocating 500 block slots versus obj.entities's 200.) As a consequence, the game had to use a separate tracking variable, obj.nentity, because obj.entities.size() would just report 200, instead of the actual amount of entities. Needless to say, having to check for `active` and use `obj.nentity` is a bit error-prone, and it's messier than simply using the std::vector the way it was intended. Also, this resulted in a hard limit of 200 entities, which custom level makers ran into surprisingly quite often. 2.3 comes along, and removes the whole system. Now, std::vectors are properly being used, and obj.entities.size() reports the actual number of entities in the vector; you no longer have to check for `active` when dealing with entities of any sort. But there was one previous behavior of 2.2 that this system kind of forgets about - namely, the ability to have holes in between entities. You see, when an entity got disabled in 2.2 (which just meant turning its `active` off), the indices of all other entities stayed the same; the indice of the entity that got disabled stays there as a hole in the array. But when an entity gets removed in 2.3 (previous to this patch), the indices of every entity afterwards in the array get shifted down by one. std::vector isn't really meant to be able to contain holes. Do the indices of entities and blocks matter? Yes; they determine the order in which entities and blocks get evaluated (the highest indice gets evaluated first), and I had to fix some block evaluation order stuff in previous PRs. And in the case of entities, they matter hugely when using the recently-discovered Arbitrary Entity Manipulation glitch (where crewmate script commands are used on arbitrary entities by setting the `i` attribute of `scriptclass` and passing invalid crewmate identifiers to the commands). If you use Arbitrary Entity Manipulation after destroying some entities, there is a chance that your script won't work between 2.2 and 2.3. The indices also still determine the rendering order of entities (highest indice gets drawn first, which means lowest indice gets drawn in front of other entities). As an example: let's say we have the player at 0, a gravity line at 1, and a checkpoint at 2; then we destroy the gravity line and create a crewmate (let's do Violet). If we're able to have holes, then after removing the gravity line, none of the other indices shift. Then Violet will be created at indice 1, and will be drawn in front of the checkpoint. But if we can't have holes, then removing the gravity line results in the indice of the checkpoint shifting down to indice 1. Then Violet is created at indice 2, and gets drawn behind the checkpoint! This is a clear illustration of changing the behavior that existed in 2.2. However, I also don't want to go back to the `active` system of having to check an attribute before operating on an entity. So... what do we do to restore the holes? Well, we don't need to have an `active` attribute, or modify any existing code that operates on entities. Instead, we can just set the attributes of the entities so that they naturally get ignored by everything that comes into contact with it. For entities, we set their invis to true, and their size, type, and rule to -1 (the game never uses a size, type, or rule of -1 anywhere); for blocks, we set their type to -1, and their width and height to 0. obj.entities.size() will no longer necessarily equal the amount of entities in the room; rather, it will be the amount of entity SLOTS that have been allocated. But nothing that uses obj.entities.size() needs to actually know the amount of entities; it's mostly used for iterating over every entity in the vector. Excess entity slots get cleaned up upon every call of mapclass::gotoroom(), which will now deallocate entity slots starting from the end until it hits a player, at which point it will switch to disabling entity slots instead of removing them entirely. The entclass::clear() and blockclass::clear() functions have been restored because we need to call their initialization functions when reusing a block/entity slot; it's possible to create an entity with an invalid type number (it creates a glitchy Viridian), and without calling the initialization function again, it would simply not create anything. After this patch is applied, entity and block indices will be restored to how they behaved in 2.2. |
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This is the source code to VVVVVV, version 2.0+. For more context about this release, see the announcement on Terry's blog!
License
VVVVVV's source code is made available under a custom license. See LICENSE.md for more details.
In general, if you're interested in creating something that falls outside the license terms, get in touch with Terry and we'll talk about it!
Authors
- Created by Terry Cavanagh
- Room Names by Bennett Foddy
- Music by Magnus Pålsson
- Metal Soundtrack by FamilyJules
- 2.0 Update (C++ Port) by Simon Roth
- 2.2 Update (SDL2/PhysicsFS/Steamworks port) by Ethan Lee
- Beta Testing by Sam Kaplan and Pauli Kohberger
- Ending Picture by Pauli Kohberger
Versions
There are two versions of the VVVVVV source code available - the desktop version (based on the C++ port, and currently live on Steam), and the mobile version (based on a fork of the original flash source code, and currently live on iOS and Android).