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| 15:27 |
sfan5 |
opinions wanted on #11775 whether this is considered breakage or not |
| 15:27 |
ShadowBot |
https://github.com/minetest/minetest/issues/11775 -- New handling of direction key bits is not fully backwards-compatible |
| 15:29 |
MTDiscord |
<Jonathon> Yes, as it affects some already existing mods |
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| 17:31 |
MTDiscord |
<luatic> sfan5: yes - modders have few controls to use, leading them to use every key combo they can get |
| 17:48 |
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| 17:49 |
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| 17:50 |
erle_on_a_train |
sfan5 i am not logged into github on this device, but the gist of it is that malicious players usually coerce the game/mod into doing the dirty out of bounds work for them. limiting player positions does not change much about that. besides, *most* out of bounds player positions do not cause a crash. |
| 17:50 |
MTDiscord |
<SX> as it is supposed to be engine instead of game imo it should allow all possible combinations, not just combinations used in some game |
| 17:51 |
erle_on_a_train |
sfan5 besides, something like compilers and ubsan will greatly help if the boundaries for functions are s16, they will be of no help if the max/min is +/-31000, unless you conjure a magical datatype that gets an unsigned integer overflow at that boundary. |
| 17:51 |
sfan5 |
erle_on_a_train: well yes, limiting player position (or even player interaction) outside of bounds wouldn't do much |
| 17:53 |
erle_on_a_train |
sfan5 my proposal to fix the various overflows would be to scrap the idea that the mapgen limit protects against overflows and make all functions well-behaved for all legal values of v3s16 they can get. this would be relatively easy. |
| 17:55 |
erle_on_a_train |
sfan5 btw i have seen stuff like lua mapgen functions that place schematics, then try to read the nodes of the area to figure out how much of it got placed and possibly repeat it to fix mapgen griefing. i bet there is a way to coerce them into looping forever if you can place nodes that you can not read. OTOH, if you crash on placing stuff out of |
| 17:55 |
erle_on_a_train |
bounds, i'd bet money on *that* being abused by griefers. |
| 17:56 |
sfan5 |
I have still not seen indication that mapgen touches 31000 |
| 17:57 |
sfan5 |
if lua mapgens place stuff far outside of their indicated area it is on them to deal with consequences or handle edge cases |
| 17:57 |
erle_on_a_train |
mapgen doesn't need to touch it actually. i do have a world that actually renders up to 31007, which i find a bit weird, bc i thought minetest does not render the outermost shell. |
| 17:58 |
erle_on_a_train |
the thing with using gadgets is used a lot btw |
| 17:58 |
erle_on_a_train |
like making the game do things for you |
| 17:59 |
erle_on_a_train |
i have used two different ways to make water in a nether dimension (where players can't place water) by coercing the game to place it there (and no, not by melting ice). i also removed unremovable blocks (“bedrock”) by making minetest spawn a structure |
| 17:59 |
erle_on_a_train |
inside the unremovable blocks |
| 18:01 |
erle_on_a_train |
sfan5 a good start would be to try emerging stuff outside bounds btw. |
| 18:01 |
sfan5 |
a good start to what?! |
| 18:02 |
erle_on_a_train |
to get mapgen to place stuff there, i think? i tought emerge makes mapgen do wok |
| 18:02 |
erle_on_a_train |
work |
| 18:02 |
erle_on_a_train |
maybe i am wrong? |
| 18:02 |
erle_on_a_train |
as i pointed out, the only real breakdown of mapgen is that at 31000 biomes are hardcoded to stop working. but the whole mapgen stuff does not matter. |
| 18:04 |
erle_on_a_train |
in the end, all functions should work inside an area. and that area has bounds. if you choose the bounds of s16, you get assistance in making the functions work from compiler warnings and ubsan. if you choose +/- 31000 (which seems weird, bc s16 bounds are asymmetric around 0, they are +32767/-32768 i think), no instrumentation will help you. |
| 18:05 |
erle_on_a_train |
and besides that, you'll get a lot of bugs at the boundary, but i keep saying that and i'm kinda sick of it. |
| 18:05 |
erle_on_a_train |
i just want a) griefers to not crash servers b) mod authors to do as little as possible |
| 18:07 |
erle_on_a_train |
sfan5 i have the feeling that others think i have some hidden nefarious reason for wanting another boundary. do you think that? |
| 18:08 |
sfan5 |
I just think it doesn't make sense |
| 18:09 |
erle_on_a_train |
that's because you do not think about it from the perspective of an attacker, i guess |
| 18:10 |
erle_on_a_train |
i really think it's that. everyone in this chat is smart enough to crash minetest if given the task. |
| 18:10 |
erle_on_a_train |
but you do not try, because why should you. |
| 18:10 |
erle_on_a_train |
meanwhile, the anarchy server “cheats are allowed” crowd encounters ppl that find it really funny to take down servers |
| 18:11 |
erle_on_a_train |
i mean, other servers encounter them too |
| 18:11 |
erle_on_a_train |
but in the anarchy server context, those ppl boast about it, then someone say “haha i do not believe it”, then they do it, we get a trace and try to fix it |
| 18:12 |
erle_on_a_train |
and also the cheat client devs fix the most glaring issues themselves |
| 18:13 |
erle_on_a_train |
sfan5 i think the focus on “but mapgen would not place anything there” is totally misleading. what if someone manages to spawn a nether portal at the coordinates? |
| 18:13 |
erle_on_a_train |
(it was fleckenstein i believe who fixed entityspeed exploit?) |
| 18:14 |
erle_on_a_train |
sfan5 btw you can keep asking how specific crashes work, but when i am being intentionally vague, then it is because the bad ppl read bug reports too. |
| 18:15 |
erle_on_a_train |
not because i want to make fun of you or appear overly smug |
| 18:15 |
erle_on_a_train |
(i think i appear smug enough tbh) |
| 18:15 |
Pexin |
hahahaha |
| 18:15 |
sfan5 |
if you want bugs fixed that you think deserve secrecy report them privately |
| 18:15 |
sfan5 |
being vague in public helps exactly nobody |
| 18:16 |
erle_on_a_train |
i have said before, i am keeping back with stuff that i have not seen in the wild unless i have a fix. |
| 18:16 |
erle_on_a_train |
bc i think it is much less likely that ppl will latch onto the wrong solution if i say “here is the problem and here is the patch” |
| 18:16 |
erle_on_a_train |
i mean they can still criticize the patch |
| 18:17 |
sfan5 |
okay, I conclude you are not actually interested in fixing crash bugs |
| 18:17 |
erle_on_a_train |
i am |
| 18:17 |
sfan5 |
doing a disservice to everyone is your choice but don't expect not to be criticized for it |
| 18:18 |
erle_on_a_train |
true |
| 18:18 |
erle_on_a_train |
but the thing is, i think that some of the fixes make it *worse* than doing nothing |
| 18:19 |
sfan5 |
hard to imagine by which measure going from "crash" to "no crash" could not be considered an improvement |
| 18:19 |
erle_on_a_train |
sfan5 i do not believe privately reporting anything would change it |
| 18:20 |
erle_on_a_train |
well i have a working lua solution for the minetest.get_nodes_in_area thing |
| 18:21 |
erle_on_a_train |
so it's not like it can get *better* from my POV unless the engine matches that. |
| 18:22 |
erle_on_a_train |
(it can get worse though, by making other stuff not work) |
| 18:22 |
erle_on_a_train |
cora even offered it to minetest_game |
| 18:27 |
erle_on_a_train |
regarding clamping on the player position, that is misrepresenting the problem a lot |
| 18:27 |
erle_on_a_train |
i do not know about minetest, but in other applications you can for example have problems with denormals |
| 18:27 |
erle_on_a_train |
https://en.wikipedia.org/wiki/Subnormal_number |
| 18:29 |
erle_on_a_train |
sfan5 we may fundamentallly agree on how to write reliable software though, could that be? i think the only way to be sure is to define a grammar for each function and make sure that everything that matches the grammar works and everything that does not match the grammar returns with a status code indicating error. if one component gives data to |
| 18:29 |
erle_on_a_train |
another, the best way to make that work is to make illegal stuff unrepresentable. |
| 18:30 |
erle_on_a_train |
sfan5 i guess you have a different opinion? |
| 18:31 |
erle_on_a_train |
(in this case: having fuctions work with every possible v3s16 means that out of v3s16 bounds coords are truly unrepresentable, whereas ±31000 bounds mean that they are still representable in v3s16) |
| 18:32 |
erle_on_a_train |
btw, one case of a sanitization bug that is abused is that players tp to illegal coordinates, then log out |
| 18:32 |
erle_on_a_train |
they will be at their spawn after login |
| 18:46 |
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| 21:09 |
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| 22:24 |
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| 22:29 |
v-rob |
Hey all, slowly trying to get back into development here again, specifically in the proper Unicode text rendering sector. So, my question: how do we deal with potentially adding hard dependencies? |
| 22:30 |
v-rob |
Since there's no way to do Unicode right without external libraries |
| 22:42 |
sfan5 |
which library are you thinking about |
| 22:53 |
v-rob |
Well, I'm not entirely certain, since there are a few possibilities (I'm still researching), but one such library is Pango, which is what GTK and Firefox on Linux uses for text-rending internally. |
| 22:56 |
v-rob |
But mostly libraries that are probably of moderate size |
| 23:02 |
sfan5 |
haven't worked with pango but I don't think I'll be a fan |
| 23:03 |
v-rob |
Honestly, I'm not either, but the quest is to find a text layout engine, of which Pango appears to be the most popular |
| 23:04 |
v-rob |
For instance, Pango prefers to use Cairo, so that'd be two dependencies unless I write my own OpenGL backend for it |
| 23:07 |
v-rob |
Short of a text-layout engine, I'd need to use a lower level text-shaping library, which would make perfect single-line Unicode, but there's no guarantee that I'd get the paragraph-level Unicode right |
| 23:08 |
sfan5 |
what does a text layout engine do that we couldn't do ourselves or with help of smaller libraries? |
| 23:12 |
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| 23:13 |
v-rob |
So, a bit of context: text-shaping is taking a string and turning it into positions for you to draw glyphs at. This is totally infeasible to do ourselves, which is the source of a lot of our Unicode problems. There's basically only one cross-platform library for this, which is HarfBuzz. |
| 23:14 |
v-rob |
As for text-layout, that's everything else, i.e. bidirectionality, fonts that change style in the middle, line breaking and paragraphs, hyphenation, etc. |
| 23:14 |
v-rob |
This sums it up: https://harfbuzz.github.io/what-harfbuzz-doesnt-do.html |
| 23:17 |
v-rob |
I don't fully know if it's feasible to implement text-layout if we have a text-shaping library, but I'm erring on the side of probably not. |
| 23:18 |
sfan5 |
well fribidi would take care of the first, changing style is what we do ourselves anyway |
| 23:18 |
v-rob |
There's a lot to consider that I don't know anything about, e.g. how different languages lay out paragraphs or how word breaking occurs for them |
| 23:18 |
sfan5 |
linebreaking, paragraphs: dunno, doesn't hypertext in formspecs have this already? |
| 23:19 |
v-rob |
I mean with Unicode and different languages. How does e.g. Chinese break lines and paragraphs? I have no idea myself. |
| 23:21 |
v-rob |
It's not fun :/ |
| 23:22 |
sfan5 |
and generally I think the aim should be to do text rendering reasonably well (better than now); MT is a game engine which also needs to display text, but that's not its primary purpose |
| 23:23 |
sfan5 |
...because getting the last 10% right is probably 90% of the work |
| 23:23 |
v-rob |
Heh, yeah |
| 23:24 |
v-rob |
So, I'd say that the minimum libraries we'd need for pretty good Unicode are probably HarfBuzz and fribidi |
| 23:24 |
v-rob |
HarfBuzz and ICU for slightly better, but ICU's pretty chunky |
| 23:24 |
sfan5 |
those are unproblematic |
| 23:24 |
v-rob |
And Pango for the best, but gross |
| 23:24 |
sfan5 |
(hb + fribidi I mean) |
| 23:25 |
v-rob |
That sounds reasonable. I guess I will work with those then. |
| 23:27 |
v-rob |
If I find a better/smaller/nicer text-layout engine than Pango, I'll bring it up. |
| 23:30 |
MTDiscord |
<exe_virus> It's always interesting how dependencies are chosen based on simplicity and size. It's not just us, but jsut about everyone. It's not something often thought about when designing a library. I.e. reducing loc |
| 23:32 |
v-rob |
It's also dependency chains -- I don't want to bring in Cairo. |
| 23:32 |
MTDiscord |
<exe_virus> fair |
| 23:33 |
MTDiscord |
<exe_virus> on the topic of dependencies.... What about small file type deps like gltf, webp, avix, midi, opus, etc? |
| 23:33 |
MTDiscord |
<exe_virus> generally okay? |
