Adds Documentation of Optional Features

doc/README.md

@@ -12,3 +12,4 @@ addon. Each class is separated into it's own file, named accordingly.
 * [WasmHelper](./WasmHelper.md)
 * Miscellaneous
   * [Importing](./misc/Importing.md)
+  * [Features](./misc/Features.md)

doc/misc/Features.md

@@ -0,0 +1,98 @@
+# Features
+
+`godot-wasm` contains many features that can be enabled or disabled at compile time.
+It can be specified by setting the `features` variable, each feature separated by comma.
+To disable default feature, pass `--no-default-features` into `BUILD_EXTRA_ARGS`.
+Example command:
+
+```
+just features=feat1,feat2,feat3 command
+```
+
+## Feature Flags
+
+### Memory Limiter
+
+* Feature: `memory-limiter`
+* Default: true
+
+Enables memory limiter to limit memory usage.
+By default it's set to unlimited.
+Note that the limiter is only approximate and should not be relied to provide hard limit.
+
+### Epoch-based Timeout
+
+* Feature: `epoch-timeout`
+* Default: true
+
+Enables epoch-based timeout mechanism to stop possible hang.
+Default timeout is 5s.
+Default precision is 20ms.
+
+### Object Registry (Legacy)
+
+* Feature: `object-registry-compat`
+* Default: true
+
+Enables legacy registry-based Godot value manipulation.
+Needs to be enabled via config option.
+
+### Object Registry (New)
+
+* Feature: `object-registry-extern`
+* Default: true
+
+Enables extern-based Godot value manipulation.
+Needs to be enabled via config option.
+
+### Object Registry
+
+* Feature: `object-registry`
+* Default: true
+
+Enables both `object-registry-compat` and `object-registry-extern`.
+
+### WASI 0.1
+
+* Feature: `wasi`
+* Default: true
+
+Enables WASI 0.1
+
+### WASI 0.2
+
+* Feature: `wasi-preview2`
+* Default: false
+
+Enables WASI 0.2
+
+### Godot Component
+
+* Feature: `godot-component`
+* Default: false
+
+Enables component-based Godot value manipulation.
+
+### WASM Threads Proposal
+
+* Feature: `wasm-threads`
+* Default: false
+
+Enables WASM threads proposal, allowing use of shared memory,
+atomic instruction, and notification.
+Note that multi-threading is a separate thing and currently cannot be done inside WASM code.
+
+### Deterministic WASM
+
+* Feature: `deterministic-wasm`
+* Default: false
+
+Enables config options that make WASM code execution more equivalent across CPU architecture.
+Note that this feature is experimental and may incur performance penalty.
+
+### Precise Timeout
+
+* Feature: `more-precise-timer`
+* Default: false
+
+Increase epoch timeout precision to 1ms.