update docs

README.md

@@ -7,6 +7,15 @@ my silly little ecs engine for odin and raylib :3
 ## contents
 - [install](#install)
 - [usage](#usage)
+  - [systems](#systems)
+  - [components](#components)
+  - [spawn entities](#spawn-entities)
+  - [query](#query)
+  - [plugins](#plugins)
+  - [signals](#signals)
+  - [timers](#timers)
+  - [ui](#ui)
+  - [tween](#tween)
 
 ## install
 clone this repo in your project directory
@@ -39,15 +48,21 @@ main :: proc() {
 ### systems
 systems are procedures that run on set schedules
 
-a schedule just determines when a producure runs\
-schedules are:
-- STARTUP
-- UPDATE
-- DRAW
+a schedule just determines when a procedure runs\
+there are 8 of them, and `run()` walks them in this order:
 
-`STARTUP` runs once at the start of an app\
-`UPDATE` runs every frame\
-`DRAW` runs every frame *after* update, and makes draw calls to raylib\
+- `STARTUP` — once, before the first frame
+- `PRE_UPDATE` — every frame, first thing
+- `UPDATE` — every frame, your main logic
+- `POST_UPDATE` — every frame, last stop before drawing (`signal_system` clears the signal buses here)
+- `PRE_DRAW` — every frame, opens the raylib frame (`DefaultPlugin` calls `BeginDrawing` + clears the background here)
+- `DRAW` — every frame, inside the frame — this is where your raylib draw calls go
+- `POST_DRAW` — every frame, closes the raylib frame (`DefaultPlugin` calls `EndDrawing` here)
+- `DESTROY` — once, after the loop exits (`DefaultPlugin` calls `CloseWindow` here)
+
+so: `STARTUP` runs once up front, the six update/draw ones run every frame in that order, `DESTROY` runs once when the window closes.
+
+systems registered on the same schedule run in registration order — whoever was `add_system()`ed first runs first (that includes the systems your plugins add, so `add_plugin(&app, ecs.DefaultPlugin)` before your own systems means shoal's defaults run first).
 
 ```odin
 main :: proc() {
@@ -80,6 +95,8 @@ and create it's storage
 Example: ecs.Storage(ExampleComponent)
 ```
 
+shoal ships a few built-ins already declared as globals, so there's nothing to create — just pass `&ecs.Window`, `&ecs.Cursor`, `&ecs.Sprite` or `&ecs.Transform`. `DefaultPlugin` reads and writes them: it opens the window from `Window`, keeps `Cursor` on the mouse, and draws every `Sprite` at its `Transform`.
+
 ### spawn entities
 create a new entity with `spawn_entity()`
 
@@ -98,8 +115,16 @@ main :: proc() {
 }
 ```
 
+or fill it in on the spot with the data overload
+
+```odin
+main :: proc() {
+  ecs.add_component(entity, &Example, ExampleComponent{...})
+}
+```
+
 ### query
-since components are saved in storage next to their entity, you can loop through a Storage and pick out what you like
+since components are saved in storage next to their entity, you can loop through a Storage and pick out what you like. `slice()` and `slice_entity()` pair up by index: `entities[i]` owns `components[i]`
 
 ```odin
 main :: proc() {
@@ -111,6 +136,8 @@ main :: proc() {
 }
 ```
 
+one caveat: `slice()` hands back the storage's live array, not a copy, so adding components afterwards can reallocate it out from under you — don't hold one across `add_component()` calls.
+
 or if you know your storage only has one entry use `single()`
 
 ```odin
@@ -118,6 +145,17 @@ main :: proc() {
   component, entity_id := ecs.single(&Example)
 }
 ```
+
+and once you have an entity id, `get_component()` reaches into any storage to get that entity's copy of the component — handy for components that live alongside another one (a sprite's `Transform`, say)
+
+```odin
+main :: proc() {
+  component, entity_id := ecs.single(&Example)
+  other := ecs.get_component(entity_id, &OtherExample)
+}
+```
+
+no existence check though: only ask for entities you know are in that storage.
  ### plugins
 plugins are just a procedure that takes `App` as a parameter, meaning it can make changes to `app`, just like main()
 
@@ -136,6 +174,8 @@ main :: proc() {
 
 plugins make your scripts very reuseable. in fact, much of shoal's default behaviors come from plugins via `DefaultPlugin()`
 
+run() fires every plugin in the order you added them, once, before the STARTUP systems — so everything they register is in place before anything executes
+
 ### signals
 signals are structs your systems can talk to each other with. one system writes a signal with data, another system reads it later in the same frame — as long as the reader runs before `signal_system` clears the buses at POST_UPDATE (see the caveat at the end of this section)
 
@@ -165,3 +205,46 @@ scheduling caveat: every system sees exactly the signals written since the last
 - systems running before POST_UPDATE (STARTUP/PRE_UPDATE/UPDATE/early POST_UPDATE) see same-frame writes
 - a DRAW system sees none of them — POST_UPDATE already cleared the bus. it only sees signals written after POST_UPDATE by an earlier system in the same frame (say, one DRAW system reacting to another's write)
 - writes made after POST_UPDATE survive the rest of the frame and are picked up by the next frame's PRE_UPDATE/UPDATE systems, then cleared at the next POST_UPDATE — so the next frame's DRAW never sees them either
+
+### timers
+timers are named countdowns. `start_timer()` starts one (or restarts one already stored under that name), and `get_timer()` reads it back — anything that never started or already finished reads back zeroed, so a nonzero `lifetime` means "still ticking"
+
+```odin
+example_system :: proc() {
+  if ecs.get_timer("cooldown").lifetime != 0 {return} // still cooling down
+  ecs.start_timer(0.5, "cooldown")
+}
+```
+
+timers tick down every frame in `run_timers`, which `DefaultPlugin` registers at UPDATE. when one runs out its entry is reset to `Timer{}` — that's the auto-clear, and why `get_timer()` goes back to zero when you've waited it out.
+
+on expiry a `TimerFired{name = ...}` signal is *meant* to be queued for `read(TimerFired)` — wip: as written the reset zeroes the entry before the name is read, so `TimerFired` currently never fires (reading the timers themselves works fine). once that's fixed the usual signal caveat applies: a reader has to run before `signal_system` clears the buses at POST_UPDATE, see the end of the [signals](#signals) section
+
+### ui
+`shoal/ui` wraps microui with its own plugin. add it before any system that wants to draw ui
+
+```odin
+import ui "shoal/ui"
+import mu "vendor:microui"
+
+main :: proc() {
+  ecs.add_plugin(&app, ui.UIPlugin)
+  ecs.add_system(&app, ecs.DRAW, my_ui)
+}
+```
+
+`ui.UIPlugin` registers `init()` at STARTUP (uploads microui's atlas texture), `begin()` at PRE_DRAW (forwards raylib input and starts the frame), frees the frame's temp memory and runs `end()` at POST_DRAW (renders the ui), and `destroy()` at DESTROY.
+
+your system builds the ui against the context `get_ctx()` hands back during the frame
+
+```odin
+my_ui :: proc() {
+  if mu.begin_window(ui.get_ctx(), "hello", {100, 100, 100, 100}) {
+    defer mu.end_window(ui.get_ctx())
+    mu.label(ui.get_ctx(), "Hello, world")
+  }
+}
+```
+
+### tween
+wip: tweens don't do anything yet. `tween.odin` ships `Tween`, `start_tween()`, `create_tween()` (a stub that returns an empty `Tween` and ignores its arguments), `update_tween_system()` (empty, and no schedule registers it) and a few sine easing helpers nothing calls — don't build on it. the `EASE_IN`/`EASE_OUT`/`EASE_IN_OUT` constants are ids for the unused `Tween.ease` field.