MSC3230: Spaces top level order #3230
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BillCarsonFr
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Co-authored-by: Michael Telatynski <7t3chguy@googlemail.com>
turt2live
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Co-authored-by: Erkin Alp Güney <erkinalp9035@gmail.com>
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| As defined per `room tagging`ordering information is given under the order key as a number between 0 and 1. The numbers are compared such that 0 is displayed first. Therefore a room with an order of 0.2 would be displayed before a room with an order of 0.7. If a room has a tag without an order key then it should appear after the rooms with that tag that have an order key, fallbacking then to roomID lexical order. | ||
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| This alternative has been discarded becaused perceived as confusing in regards of tags intentions. |
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confusing how? It seems like a natural fit for reusing existing structures in Matrix, which is ideal.
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It's also much easier to work with than lexicographical strings.
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Caused infinite problems when we first did it due to truncation and rounding and ieee representation quirks. It didn't proove much easier
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@turt2live looks like this has an implementation vector-im/element-android#3502
Also in web matrix-org/matrix-react-sdk@21fc386
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Also the spec explicitly calls out tags without a u prefix as reserved for application internal uses, which in this case the tag would be used for ordering spaces instead of as a tag.
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The "space folder" future consideration overlaps with spaces themselves? A folder could be a space tagged with "folder display" account data. A similar approach could be taken for the "space pinning" future consideration. Pinned spaces could be children of a space tagged with "pinned spaces" account data. |
| should appear after the rooms with that tag that have an order key, fallbacking then to roomID lexical order. | ||
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| This alternative has been discarded becaused perceived as confusing in regards of tags intentions. | ||
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| ## Alternatives | |
| Have space child room pointers in MSC1769 profile rooms, hence have the ordering per-profile, | |
| rather than per-account. | |
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| In order to find mid points between two orders strings, the `order` string can be considered as | ||
| a base N number where N is the length of the allowed alphabet. So the string can be converted | ||
| to a base 10 number for computation and mid point computation, then converted back to base N. |
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I don't think this algorithm works well enough to go into the spec as a recommended algorithm.
First issue is for an alphabet "A-Z" it considers "B" and "BA" to be the same thing, which they're not. Collisions would become an issue.
For A..B and limit 4
0
A 8
AA 12
AAA 14
AAAA 15
AAAB 16
AAB 16
AABA 17
AABB 18
AB 16
ABA 18
ABAA 19
ABAB 20
ABB 20
ABBA 21
ABBB 22
B 16
BA 20
BAA 22
BAAA 23
BAAB 24
BAB 24
BABA 25
BABB 26
BB 24
BBA 26
BBAA 27
BBAB 28
BBB 28
BBBA 29
BBBB 30
One could fix this by treating the string as a base N + 1 and padding the end of the string with the new character.
But you get gaps in that case.
For A..B and limit 4
0
A 27
AA 36
AAA 39
AAAA 40
AAAB 41
AAB 42
AABA 43
AABB 44
AB 45
ABA 48
ABAA 49
ABAB 50
ABB 51
ABBA 52
ABBB 53
B 54
BA 63
BAA 66
BAAA 67
BAAB 68
BAB 69
BABA 70
BABB 71
BB 72
BBA 75
BBAA 76
BBAB 77
BBB 78
BBBA 79
BBBB 80
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Ah, I just noticed that the example also highlights this.
"a" = 65*(95^0)
"z" = 90*(95^0)
"az" = 65*(95^1) + 90*(95^0)
Simplified, the calculated values are.
"a" = 65
"z" = 90
"az" = 6265
Sorting them lexicographically, "az" is between "a" and "z", but the numbers don't reflect this.
Worse yet, the number of possible strings between "a" and "z" should be massive! Much bigger than 2^32.
But this algo says the available strings is "90 - 65", which is just 25.
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The issue is that we need a representation that allows to easily compute midpoints / interval in between to orders.
Nonetheless it's true that string to base representation is not respecting lexicographic order (as we are padding strings to be same length).
I might update MSC to reflect the need for padding or state to use stringToBase to compare
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@turt2live looks like this has an implementation element-hq/element-android#3502 |
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I've added the known implementations to the PR's description. These appear to constitute appropriate implementations of the MSC, do you agree @BillCarsonFr? |
| This alternative has been discarded as it won't scale, could reach event content size limit, and is | ||
| less flexible as a way to define order compared to [0,1]. |
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There is no size limit for account data events (otherwise m.direct would break). A bigger concern is that clients often break the m.direct event when updating the list in it, because it is racy, which would apply here too, but I very much doubt users will be in so many top level spaces, that this will ever matter here.
| On tap would expand the pannel. | ||
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| ## Alternatives | ||
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Not that I think it is a particularly good idea, but one could also create a private, invisible top level space, that orders its children by the normal rules. Only difference would be that that top level space is not shown in clients and is only used for ordering.
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| ## Future considerations | ||
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| __Space Pinning__: The room `m.space_order` content could be extended by adding categories like `pinned`. |
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Is this about pinning non-top level spaces?
| __Space Folder__: In order to save vertical space, content could be extended to define folders | ||
| and space with same folder could be represented as a single entry in the space pannel. | ||
| On tap would expand the pannel. |
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if defining folders and spaces with same folder key as folder id will be represented as single entry, how the folder entry will be ordered around other top-level spaces or folders? does folder key is also a lexicographical order key?
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