A box in pixels was composed back up the move chain, on a grid fine enough that the walk rounded once, while a widget's offer was threaded down through its ancestors' offers. Two routes to one length, which is what `Holds::through` allowed for -- and the offer's route broke at a region node. `offered_region` fell back to `UiRegion::FULL` there, and `redraw` resolved that against the node's slot entry, which holds the box its parent *placed* the node in. Under a `Scroll` that is as long as the content rather than the viewport, so everything below was re-asked at a width its own answer had produced and the old answer confirmed itself: shrinker seed 220 on `reorder` left a widget 290px out. `ActiveData` now keeps a widget's box as lengths of its parent's box -- `given_len`, and `offer_len` for the box it was first asked about -- and `DrawInfo` carries the pixel lengths, threaded down one `Len::to_px` at a time: the box its parent gave it, then the part of that box its own answer placed the drawing in, which `placed_lens` states once for both `placed_box` and the walk. `Painter::px_size` and `px_len` read that value, and `UiRenderState::asked_px` takes the same steps back up the parent chain where a local redraw starts part-way down the tree. Neither chain has a coordinate frame in it, so neither can break at a region node, and warm and cold reach every length by the same expression. Three things follow. `Holds::through` is the exact preimage of `px + floor(rel * box)` -- two divisions, no allowance, the whole of a box mapping back to itself. A local redraw asks in the box its parent gave it and only where that box is as long as the offer, which retires `redraw`'s third ask and the region-node exception beside it; `draw_inner` places the answer inside that box itself. And symbolic regions are left to the GPU, hit testing and remaps, where `Moves::resolve` is the only walk: `wide.rs`, `Moves::compose`, `Moves::size_of`, `px_of`, `px_region`, `offered_region` and `slot_wide` are gone, 252 lines of `core/` net. `px` is deliberately not stored beside those lengths. A resize every widget's `Holds` admits redraws nothing, so a stored pixel length would be stale on every widget in the tree with nothing on it to say so, and refreshing it costs a walk down every reused subtree on the resize path. Instructions:u, medians of 21 runs, seed 1 at depth 8: | phase | before | after | | | --- | ---: | ---: | ---: | | `cold`, 200 frames | 313.1M | 312.9M | -0.04% | | `resize` | 408.1M | 405.6M | -0.61% | | `many` | 1,924M | 1,756M | -8.75% | | `scroll` | 357.3M | 323.4M | -9.49% | | `repaint` | 363.3M | 315.4M | -13.18% | `cold` and `resize` have all twenty-five work counters identical, so those two rows say the draw path costs the same threaded as composed. The other three do less work: `repaint` goes from 23 draw requests and 13 widget draws a frame to 1 and 1, `scroll` from 20 and 11 to 8 and 2, `many` from 273 and 186 to 207 and 157. Primitive writes are unmoved in every phase. Verified: `view`, `minimal`, `random`, `tabs` and `text` render byte-identical at 1920x1200 against `5b78002`, as does the `tabs` touch replay before and after the gesture, and a live resize of `random` to 1280x800 is identical both to the old head's and to a cold render at that size. The oracle passes 100 seeds in release and 120 in debug -- the debug run is the one that exercises the `Holds` assertion -- and the fifteen shrinker cases pass at 400 seeds of depth 5 and 1000 of depth 6. Seed 220 is `unsettled::a_widget_under_a_region_node_is_asked_in_the_box_that_node_was_offered`, which needs both halves of this to fail: the old chain with the old allowance passes it, and the old chain with the exact preimage does not. `AGREE_STEPS` stays 2. One step passes the 100-seed oracle and fails the 400-seed shrinker on `resize-size` by 0.002 px, so what is left there is the resize path re-expressing a part as a fraction of a box that changed length, not a length reached two ways. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
iris
My experimental attempt at a rust ui library (also my first ui library).
It's currently designed around using retained data structures (widgets), rather than diffing generated trees from data like xilem or iced. This is an experiment and I'm not sure if it's a good idea or not.
Examples are in examples, eg. cargo run --example tabs.
Goals, in general order:
- does what I want it to (text, images, video, animations)
- very easy to use ignoring ergonomic ref counting
- reasonably fast / efficient (a lot faster than electron, save battery life, try to beat iced and xilem)
dev details
not targeting web rn cause wanna use actual nice gpu features & entire point of this is to make desktop apps / not need a web browser
general ideas trynna use rn / experiment with:
- retained mode
- specifically designed around wgpu so there's no translation
- postfix functions for most things to prevent unreadable indentation (going very well)
- events can be done directly where you draw the widgets
- almost no macros in user code & actual LSP typechecking (variadic generics if you can hear me please save us)
- relative anchor + absolute offset coord system (+ "rest" / leftover during widget layout)
- single threaded ui & pass context around to make non async usage straightforward (pretty unsure about this)
- widgets store outside of the actual rendering so they can be moved around and swapped easily (unsure about this but seems to work good for now)
under heavy initial development so not gonna try to explain status, maybe check TODO for that; sizable chance it gets a rewrite once I know everything I need and what seems to work best
it's called iris because it's the structure around what you actually want to display and colorful