Send HUD flags only if changed

[appgurueu]

Supposedly fixes luanti-org/minetest_game#2900

[corarona]

yes please <3

could this be done with all object properties? This is a very easy thing to do wrong for modders.

[corarona]

actually mtg itself is doing this wrong: luanti-org/minetest_game#2900

[lhofhansl]

A looong time ago I fixed a bug in the nssm mod (explanation here, got merged in tenPlus1's fork later: NPXcoot/nssm#22).

Not the same, but similar problem, where a mod can send block updates that starve out all other block updates from the server (the client stopped loading any other blocks). Definitely something the engine should fix - to some extend (f.e. not sending blocks that have not changed).

(Posted on wrong issue before)

[appgurueu]

actually mtg itself is doing this wrong: minetest/minetest_game#2900

I guess I do have to include reasoning as to why this belongs in the engine and not the games/mods using the API, so here it is:

1. The engine can do it very efficiently, as it already operates on the bitsets (u32). Lua on the other hand operates on tables due to the provided API.
2. This means all mods will automatically get this fixed without having to change their implementation. Abondoned mods or games might benefit from this.
3. This avoids both code duplication (if player:hud_get_flags().something then ... end all the time) or having to create an API myapi.hud_set_flags_if_unchanged(player, flags) which would then have to be adopted or again be duplicated. Mod code can continue being straightforward, well-readable and fast.

[corarona]

4. It isn't really helpful to have the (default) option to resend properties that haven't changed.

Literally every occurrence of hud_set_flags (and set_properties and set_bones and maybe others ?) in a game/mod needs to check first ideally (we usually don't if it just happens once but it is still redundant traffic).

[SmallJoker]

As an optimization, this is fine by me. HUD flags are sent as reliable and often updated in mods. However, mods should still try to be efficient in general, especially because other functions do not have such redundancy checks (HUD elements).