ipyronic

Can confirm in 1.21.1

Player-launched fireworks accelerate their Y motion by +0.04 each tick and dispenser-launched fireworks don't have the Y acceleration.

The acceleration difference can be observed with a command block set to Repeat the following command:

/tellraw @p {"nbt":"Motion[1]","entity":"@e[type=firework_rocket]"}

The server had no mods. It was a completely vanilla 1.19 server jar.

I'm unsure if the 'relates to' issue is actually related, since there's no IndexOutOfBoundsException in REALMS-1656 and the sizes are wildly different. But maybe that's why they aren't considered 'duplicates' and just 'relates to'.

I'm also not sure if my issue was caused by a minecraft client attempting to access the server. I'm doubtful that it was a legitimate player login attempt.

@Chava. Many thanks for mentioning LazyDFU, it lowered my startup thermals significantly.

I've noticed that minecraft's resource usage has been obnoxious since like v1.13 or something. Apparently that's also when DataFixerUpper came into existence (according to google).

If DFU's purpose is to update my old world then I don't understand why it would be initialized during startup... It isn't needed during startup. I have no worlds for it to update, so those resources are literally being wasted.

Every time minecraft launches to the title screen it puts my i9-9900K through a thermal-cycle stress test by quickly ramping up +40 Celsius and then right back down -40 C after the title screen is loaded 15 seconds later.

My friend's computer sometimes has a thermal shutdown. It's that bad. I don't know why they haven't gone in and optimized this yet. You don't need a new bug report in order to say to yourself "Hmm, we really should optimize the startup or implement an artificial slow-down to make it less intensive...". Especially if someone has already pointed out a major cause AND a fix.

This bug report just boggles my mind that nothing has been done with the information gathered in it (and its associated duplicates).

I took my liquid-cooling apart for maintenance and applied new thermal paste to my CPU just to make sure the problem wasn't on my end. It's not my cooling, it's minecraft's vanilla startup code.

That slime launcher video is a good demonstration to compare the boats that do slide to the minecarts which don't. I highly doubt it affected the test, but it would have been nice to see some separation between the two minecarts in the middle so that we know they aren't interacting with each other or the adjacent floor block.

I can reproduce this practically every time I try. Simply jump, wait a fraction of a second, and then ride the entity before you start falling down again. Latest versions tested: Vanilla 1.12.1, Spigot 1.12.1

Must be on a multiplayer server (not singleplayer) with allow-flight off and you must be in survival/adventure mode (not creative). It doesn't matter if you are OP or not.

Happens when riding any entity (even ones which normally can't be ridden such as armor stands). I first discovered this bug while riding armor stands using a chair plugin on a spigot server.

In response to Kaiwen He's comment: It still happens to me for boats in vanilla 1.12.1.
In response to Yottazoid's comment: I cannot get it to happen while I am falling down, only when going up D:

"Works As Intended"
Welp, that's unfortunate, since the current code doesn't render stuff the same for all users. I have three computers, and all of them display signs poorly when they're facing north/south. However, my friend has one computer and it displays just fine (we compared screenshots of the same sign). I was hoping I'd one day be able to see all signs clearly like other people can 😞

Rephrasing:
When you feed rabbits a carrot, they will not try to breed with nearby rabbits that have also been fed until you remove any remaining carrots that are in your held-item slot. They prioritize following you for the carrot instead of breeding, so you have to lose their attention somehow (drop all the carrots, switch slots, move far enough away). This also applies to older minecraft versions, not just the 1.9 snapshot specified.

Note: When a pig is fed a carrot (and there is another pig nearby that is fed), it will immediately stop following you and move toward the other pig (even if you still have a stack of carrots in your held item slot). Rabbits do not do this.

This issue might be more accurately titled "Rabbits prioritize eating over breeding".

Wouldn't it be re-applying your selected resource packs?
You selected "Done", so it should be applying them regardless of whether you already have those ones applied from before. That way it will load changes that have occurred if you edited a resource pack while you were using it o.o If it just checks and sees "Oh hey, you already had these before" and then says "I'm not going to do anything", then you will have to switch to another pack and then switch back if you want to make your resource pack file changes work. That's potentially double the lag. If you know you didn't change anything, then you should press Esc or they should add a Cancel button. A Cancel button would be nice~

Edit: Or maybe make a Re-Apply button and make the Done button only apply when the list selections are altered.

I just tested, the fire is not shown, but my player did get lit on fire from it. The smoke-like particles do appear though (just not the flame part).

Recreate by placing a hopper somewhere, then crouch and use Flint and Steel on the top of the hopper.

I redownloaded 13w04a and went back to my world I created to test stuff in the 1.5 snapshots, and the problem still happened.

However, after creating a new world, it no longer happened.
(I then went back to my first world and it continued to not drop TNT in survival. I guess there's just something wrong with my first world.)

Sorry about this...

Definitely sure that I was in Survival.

I'll try redownloading the snapshot and test again to see if something is somehow wrong with my copy.

The same thing happened for me when I tested it just now.

I would think this isn't a suggestion o.O

I view bugs as things that don't work like they should, not just things that break the game such as crashing, item duplication, lag, and messed up object rendering.

If you ask me, minecarts not sliding on ice was just something that wasn't thought about by the devs after all of this time. If someone were to directly tell them:

"Hey, you know minecarts ignore ice and treat it like any other block, right?"

I doubt they'd say:

"Yeah, it's supposed to be like that, we thought it'd be funnier if items could slide on ice, players could slide on ice, and mobs could slide on ice, but minecarts that move faster than all of those things couldn't slide on ice~"