Use B-tree collections instead of Fx hash ones

This removes a dependency. Since the collections in question should
usually be pretty small, it might also reduce memory overhead at little
cost in speed. Here are some relevant performance discussions:

  https://users.rust-lang.org/t/hashmap-vs-btreemap/13804
  https://www.reddit.com/r/rust/comments/7rgowj/hashmap_vs_btreemap/

app-proto/Cargo.lock

@@ -89,7 +89,6 @@ dependencies = [
  "lazy_static",
  "nalgebra",
  "readonly",
- "rustc-hash",
  "sycamore",
  "wasm-bindgen-test",
  "web-sys",
@@ -364,12 +363,6 @@ dependencies = [
  "syn",
 ]
 
-[[package]]
-name = "rustc-hash"
-version = "2.0.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "583034fd73374156e66797ed8e5b0d5690409c9226b22d87cb7f19821c05d152"
-
 [[package]]
 name = "safe_arch"
 version = "0.7.2"

app-proto/Cargo.toml

@@ -15,7 +15,6 @@ js-sys = "0.3.70"
 lazy_static = "1.5.0"
 nalgebra = "0.33.0"
 readonly = "0.2.12"
-rustc-hash = "2.0.0"
 sycamore = "0.9.0-beta.3"
 
 # The `console_error_panic_hook` crate provides better debugging of panics by

app-proto/src/assembly.rs

@@ -1,9 +1,8 @@
 use nalgebra::{DMatrix, DVector, DVectorView};
-use rustc_hash::FxHashMap;
 use std::{
     any::{Any, TypeId},
     cell::Cell,
-    collections::BTreeSet,
+    collections::{BTreeMap, BTreeSet},
     cmp::Ordering,
     fmt,
     fmt::{Debug, Formatter},
@@ -522,7 +521,7 @@ pub struct Assembly {
     pub tangent: Signal<ConfigSubspace>,
     
     // indexing
-    pub elements_by_id: Signal<FxHashMap<String, Rc<dyn Element>>>
+    pub elements_by_id: Signal<BTreeMap<String, Rc<dyn Element>>>
 }
 
 impl Assembly {
@@ -531,7 +530,7 @@ impl Assembly {
             elements: create_signal(BTreeSet::new()),
             regulators: create_signal(BTreeSet::new()),
             tangent: create_signal(ConfigSubspace::zero(0)),
-            elements_by_id: create_signal(FxHashMap::default())
+            elements_by_id: create_signal(BTreeMap::default())
         }
     }
     

app-proto/src/main.rs

@@ -8,8 +8,7 @@ mod specified;
 #[cfg(test)]
 mod tests;
 
-use rustc_hash::FxHashSet;
-use std::rc::Rc;
+use std::{collections::BTreeSet, rc::Rc};
 use sycamore::prelude::*;
 
 use add_remove::AddRemove;
@@ -20,14 +19,14 @@ use outline::Outline;
 #[derive(Clone)]
 struct AppState {
     assembly: Assembly,
-    selection: Signal<FxHashSet<Rc<dyn Element>>>
+    selection: Signal<BTreeSet<Rc<dyn Element>>>
 }
 
 impl AppState {
     fn new() -> AppState {
         AppState {
             assembly: Assembly::new(),
-            selection: create_signal(FxHashSet::default())
+            selection: create_signal(BTreeSet::default())
         }
     }