Add armpack macro usage example

macro_armpack/README.md

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+Use build macro to:
+- Create trait constructor
+- Create trait init function
+- Parse exported `Scene.arm` file and auto create references to objects in scene

macro_armpack/Sources/arm/Game.hx

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+package arm;
+
+import iron.math.Vec4;
+
+@:build(arm.Macros.build())
+class Game extends iron.Trait {
+
+    function update() {
+        Cube.transform.rotate( Vec4.zAxis(), 0.01 );
+        Icosphere.transform.rotate( Vec4.yAxis(), 0.01 );
+        Torus.transform.rotate( Vec4.xAxis(), 0.01 );
+    }
+}

macro_armpack/Sources/arm/Macros.hx

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+package arm;
+
+#if macro
+
+import haxe.macro.Context;
+import haxe.macro.Expr;
+import iron.data.SceneFormat;
+import iron.system.ArmPack;
+import sys.FileSystem;
+import sys.io.File;
+
+using StringTools;
+using haxe.io.Path;
+
+class Macros {
+
+    static function build() {
+        var fields = Context.getBuildFields();
+        var pos = Context.currentPos();
+        var target = if( Context.defined('kha_krom') ) 'krom';
+        else if( Context.defined('kha_html5') ) 'html5';
+        else Context.fatalError('Only krom and html5 are supported targets for this project', pos );
+        var dir = Sys.getCwd() + target;
+        var files = FileSystem.readDirectory(dir);
+        var sceneData : TSceneFormat = null;
+        var meshes = new Array<String>();
+        for( file in files ) {
+            if( file == 'Scene.arm' ) {
+                var p = '$dir/$file';
+                sceneData = ArmPack.decode( File.getBytes(p) );
+                trace(sceneData);
+                trace(sceneData.name);
+                for( obj in sceneData.objects ) {
+                    if( obj.properties != null )
+                        for( p in obj.properties ) trace(p.name +' = '+ p.value);
+                    if( obj.type == 'mesh_object' )
+                        meshes.push(obj.name);
+                }
+                break;
+            }
+        }
+
+        var constructorExprs = new Array<Expr>();
+        constructorExprs.push(macro super() );
+        constructorExprs.push(macro notifyOnInit(init) );
+        fields.push({
+            access: [APublic,AInline],
+            name: 'new',
+            pos: pos,
+            kind: FFun({
+                args: [],
+                ret:  macro: Void,
+                expr: { expr: EBlock( constructorExprs ), pos: pos }
+            }),
+        });
+
+        var initExprs = new Array<Expr>();
+        initExprs.push( macro trace("Init") );
+        for( mesh in meshes ) {
+            fields.push({
+                name: mesh,
+                access: [APublic],
+                kind: FVar(macro: iron.object.MeshObject, macro null),
+                pos: pos
+            });
+            initExprs.push( macro this.$mesh = iron.Scene.active.getMesh($v{mesh}) );
+        }
+        initExprs.push( macro notifyOnUpdate(update) );
+
+        fields.push({
+            name: 'init',
+            access: [],
+            kind: FFun({
+                args: [],
+                ret: macro : Void,
+                expr: { expr: EBlock( initExprs ), pos: Context.currentPos() }
+            }),
+            pos: pos
+        });
+
+        return fields;
+    }
+}
+
+#end