Expect GODOT4_BIN env or godot4 executable; document toolchain requir…

…ements

.github/composite/godot/action.yml

@@ -63,15 +63,15 @@ runs:
       run: |
         runnerDir=$(echo "${{ runner.temp }}" | sed "s!\\\\!/!")
         echo "RUNNER_DIR=$runnerDir" >> $GITHUB_ENV
-        echo "GODOT_BIN=$runnerDir/godot_bin/${{ inputs.binary-filename }}" >> $GITHUB_ENV
+        echo "GODOT4_BIN=$runnerDir/godot_bin/${{ inputs.binary-filename }}" >> $GITHUB_ENV
       shell: bash
 
     # The chmod seems still necessary, although applied before uploading artifact. Possibly modes are not preserved.
     # The `| xargs` pattern trims the output, since printed version may contain extra newline, which causes problems in env vars.
     - name: "Inspect Godot version"
       run: |
-        chmod +x $GODOT_BIN
-        godotVer=$($GODOT_BIN --version | xargs || true)
+        chmod +x $GODOT4_BIN
+        godotVer=$($GODOT4_BIN --version | xargs || true)
         gitSha=$(echo $godotVer | sed -E "s/.+custom_build\.//")
         echo "GODOT_BUILT_FROM=_Built from [\`$godotVer\`](https://github.com/godotengine/godot/commit/$gitSha)._" >> $GITHUB_ENV
       shell: bash
@@ -122,7 +122,7 @@ runs:
       run: |
         cd itest/godot
         echo "OUTCOME=itest" >> $GITHUB_ENV
-        $GODOT_BIN --headless 2>&1 | tee >(grep "SCRIPT ERROR:" -q && {
+        $GODOT4_BIN --headless 2>&1 | tee >(grep "SCRIPT ERROR:" -q && {
         	printf "\n -- Godot engine encountered error, abort...\n";
         	pkill godot
             echo "OUTCOME=godot-runtime" >> $GITHUB_ENV

ReadMe.md

@@ -23,6 +23,15 @@ However, the library can serve as a playground for experimenting.
 
 ## Getting started
 
+### Toolchain
+
+You need to have LLVM installed to use `bindgen`, see [the book](https://godot-rust.github.io/book/getting-started/setup.html#llvm) for instructions.
+
+To find a version of Godot 4, the library expects either an executable of name `godot4` in the PATH, or an environment variable `GODOT4_BIN`
+containing the path to the executable (including filename).
+
+### Project setup
+
 We currently only have a GitHub version, crates.io releases are planned once more of the foundation is ready.  
 In your Cargo.toml, add:
 
@@ -51,9 +60,14 @@ To register the GDExtension library with Godot, you need to create two files rel
     ```
     res://MyExt.gdextension
     ```
+
+### Examples
+
 We highly recommend to have a look at a working example in the `examples/dodge-the-creeps` directory.
 This integrates a small game with Godot and has all the necessary steps set up.
 
+API documentation can be generated locally using `cargo doc -p godot --no-deps --open`.
+
 Support for macOS is still ongoing, there is currently **no** support for Android, iOS or WASM.
 Contributions in this regard are very welcome!
 

godot-codegen/src/godot_exe.rs

@@ -106,15 +106,15 @@ fn dump_extension_api(godot_bin: &Path, out_file: &Path) {
 }
 
 fn locate_godot_binary() -> PathBuf {
-    if let Ok(string) = std::env::var("GODOT_BIN") {
-        println!("Found GODOT_BIN with path to executable: '{}'", string);
+    if let Ok(string) = std::env::var("GODOT4_BIN") {
+        println!("Found GODOT4_BIN with path to executable: '{}'", string);
         PathBuf::from(string)
     } else if let Ok(path) = which::which("godot4") {
         println!("Found 'godot4' executable in PATH: {}", path.display());
         path
     } else {
         panic!(
-            "Bindings generation requires 'godot4' executable or a GODOT_BIN \
+            "Bindings generation requires 'godot4' executable or a GODOT4_BIN \
                  environment variable (with the path to the executable)."
         )
     }