Object trees

Objects can be added to a scene (here h2d.Scene) directly or be added to another h2d.Object creating an object tree. The child objects will inherit the transformations of the parent object they have been added to. This means whenever the parent transforms (changing the position, rotation, alpha=transparency or turning it invisible etc.) these transformations also apply to all the children that have been added to this parent object.

Sample 1

Preview

Code

class ObjectTrees extends hxd.App { // ObjectTrees
    var parent_obj  : h2d.Object;
    var a_child_obj : h2d.Object;
    static function main() {new ObjectTrees();}
    override function init() {

        // parent object placed on `s2d`
        var tile = h2d.Tile.fromColor( 0x0000FF, 120, 120 );
        var b = new h2d.Bitmap( tile, s2d );
        b.setPosition( s2d.width/2, s2d.height/2 );

        parent_obj = b; // save reference

        // 1. child (label for parent)
        var t = new h2d.Text( hxd.res.DefaultFont.get(), b );
        t.text = "parent object";

        // 2. child ("sub-bitmap")
        var tile = h2d.Tile.fromColor( 0x00FF00, 45, 45 );
        var bb = new h2d.Bitmap( tile, b );
        bb.setPosition( 30, 50 ); // will be relative to parent!

        // save second reference
        a_child_obj = bb;

        // 3. child (label for "sub-bitmap")
        var t = new h2d.Text( hxd.res.DefaultFont.get(), bb );
        t.text = "\"sub-bitmap\"";

        // control buttons
        var flow = new h2d.Flow( s2d ); flow.layout = h2d.Flow.FlowLayout.Vertical;
        var add_button = (infotext:String) -> {
            var ia = new h2d.Interactive( 250, 32, flow );
            var t = new h2d.Text( hxd.res.DefaultFont.get(), ia );
            t.text = infotext;
            return ia;
        };
        var bt = add_button( "rotate parent object (click here)" );
        bt.onClick = (e)->{ parent_obj.rotate( 0.2 ); };
        var bt = add_button( "rotate child object (click here)" );
        bt.onClick = (e)->{ a_child_obj.rotate( 0.2 ); };
        var bt = add_button( "random alpha for child object (click here)" );
        bt.onClick = (e)->{ a_child_obj.alpha = 0.1 + hxd.Math.random( 0.9 ); };
    }
}

---

Sample 2

The second sample here is a demonstration of how object trees are useful when finally having many objects "treed" together. Referencing single objects within the tree allows controlling all sub-branches of the tree, also making programming easy and powerful.

Preview

Code

class Main extends hxd.App {
    // object references
    var clock : h2d.Graphics;
    var npc : h2d.Graphics;
    // more control variables
    var clock_deltaScale = -0.01;
    var npc_moveX : Float = 0;
    var npc_moveY : Float = 0;
    var npc_deltaAlpha : Float = -0.01;
    var transitionsActive : Bool = false;
    //var npc_trans
    static function main() {new Main();}
    override function init() {
        
        clock = new h2d.Graphics( s2d );
        clock.beginFill( 0x505050 );
        clock.drawCircle( 0, 0, 90 );
        clock.endFill();
        clock.setPosition( 100, 100 );

        var face = new h2d.Graphics( clock );
        face.beginFill( 0xFFFFFF );
        face.drawCircle( 0, 0, 85 );
        face.endFill();

        var tile = h2d.Tile.fromColor( 0x0, 75, 12 ); tile.dy = -6;
        var handHours   = new h2d.Bitmap( tile, clock ); handHours.rotation = 1.5*Math.PI;
        var tile = h2d.Tile.fromColor( 0x0, 80,  8 ); tile.dy = -4;
        var handMinutes = new h2d.Bitmap( tile, clock );
        var t = new haxe.Timer(1000); // simple Haxe timer for calling a function to move the hands
        t.run = ()->{
            handHours.rotate( Math.PI/3600 );
            handMinutes.rotate(  Math.PI/60 );
        };
        // ball on hand for minutes will move with the hand/indicator
        var g = new h2d.Graphics( handMinutes ); // because it's its child
        g.setPosition( 60, 0 ); g.beginFill( 0x0 ); g.drawCircle( 0, 0, 8 );

        npc = new h2d.Graphics( s2d );
        npc.setPosition( 300, 300 );

        // NPC's face
        npc.beginFill( 0xFFFF00 ); npc.drawCircle( 0, 0, 40 );
        // first eye
        npc.beginFill( 0x0 ); npc.drawCircle( -20, 0, 7 );
        // second eye
        npc.beginFill( 0x0 ); npc.drawCircle( 20, 0, 7 );
        // a happy mouth
        npc.beginFill( 0x0 ); npc.drawPie( 0, 10, 15, 0*Math.PI, 1*Math.PI );
        // and some eye sparkle
        npc.beginFill( 0xFFFFFF ); npc.drawCircle( -20, -5, 3 );
        npc.beginFill( 0xFFFFFF ); npc.drawCircle( 20, -5, 3 );

        var healthbar = new h2d.Graphics( npc );
        healthbar.setPosition(-50,-70);
        healthbar.beginFill( 0xFF0000 ); healthbar.drawRect( 0, 0, 100, 20 );
        healthbar.beginFill( 0x00FF00 ); healthbar.drawRect( 0, 0,  70, 20 );

        var healthbar_label = new h2d.Text( hxd.res.DefaultFont.get(), healthbar );
        healthbar_label.text = "NPC\n70 lifepoints left";
        healthbar_label.setPosition( 0, -32 );

        var npc_moveVectorLabel =  new h2d.Text( hxd.res.DefaultFont.get(), npc );
        npc_moveVectorLabel.setPosition(-50,50);
        // defining a timer to change the NPC's movement vector
        var t = new haxe.Timer(3*1000); // change moving direction every 5 seconds
        t.run = ()->{
            npc_moveX = Math.round( ((-1+(Math.random()*2))) * 100) / 100;
            npc_moveY = Math.round( ((-1+(Math.random()*2))) * 100) / 100;
            npc_moveVectorLabel.text = 'move vector (x: ${npc_moveX}, y: ${npc_moveY})';
        };

        // button to control additional transitions (clock size & NPC alpha)
        var button = new h2d.Interactive( 200, 48, s2d ); button.backgroundColor = 0xFF0000FF;
        button.setPosition( 0, s2d.height - 48 );
        var t = new h2d.Text( hxd.res.DefaultFont.get(), button ); t.text = "Click to activate\nall transitions";
        button.onClick = (e) -> {
            transitionsActive = !transitionsActive;
            t.text = 'changes on clock scale\n& NPC\'s alpha: ${ ( transitionsActive ? "active" : "inactive" ) }';
        };
    }
    override function update(dt:Float) {
        super.update(dt);
        // clock movement
        clock.x += 0.2;
        if( clock.x>400 )
            clock.x = 100;
        // npc movement
        npc.x += npc_moveX;
        npc.y += npc_moveY;
        // npc never leaves scene
        if( npc.x < 0 || npc.y < 0 || npc.x > s2d.width || npc.y > s2d.height )
            npc.setPosition( 300, 300 );
        // additional transitions: clock size & NPC alpha
        if( transitionsActive ){
            // npc changes transparency
            if( npc.alpha < 0.1 || npc.alpha > 1 )
                npc_deltaAlpha = -npc_deltaAlpha;
            npc.alpha += npc_deltaAlpha;
            // clock changes size
            if( clock.scaleX < 0.8 || clock.scaleX > 1 )
                clock_deltaScale = -clock_deltaScale;
            clock.scaleX += clock_deltaScale;
            clock.scaleY += clock_deltaScale;
        }
    }
}

Have a look at the last block of code after if( transitionsActive ){ ... Note that we only changed the clocks scale and npc's alpha and all their children – though very own objects – changed with them!

Side note: Here by using haxe.Timer we rely on simple Haxe API to provide another way besides the update method to make changes