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Using Heaps Components

DomKit is a library that can be used together with Heaps to create complex UI and integrate custom 2D components into it.

You should get install it first using: haxelib git domkit

You can then add it to your project libraries with -lib domkit (together with -lib heaps)

You can see compile and run the corresponding Heaps Sample

In order to use Domkit to create a heaps components, you simply need to implements h2d.domkit.Object and define your document in the SRC static as the following sample shows:

class SampleView extends h2d.Flow implements h2d.domkit.Object {

    static var SRC = 
        <flow class="box" vertical> 
            Hello World! 
            <bitmap src={tile} id="mybmp"/>

    public function new(tile,?parent) {


var view = new SampleView(h2d.Tile.fromColor(0xFF,32,32),s2d);
view.mybmp.alpha = 0.8;

You can read more about Domkit Markup Syntax in the reference below.

Applying CSS

You can then apply CSS at runtime to your document by using the following code:

var style = new h2d.domkit.Style();
// resource referencing res/style.css (see Heaps Resources documentation)

Here's an example CSS that can apply to previous view:

.box {
    padding : 20;
    background : #400;

Runtime CSS reload

In order to get runtime CSS reload you need to: use a hxd.Res.initLocal() so you use a local filesystem to load resources. This is only available to some platforms such as HashLink enable resources live update with hxd.Res.LIVE_UPDATE = true;

Then every time you modify your CSS file, the style will be reapplied to all your currently displayed components. Errors will be displayed in case of invalid CSS property or wrongly formatted value.

Compile time CSS strong checking

You can add an init macro that will process at compile time your CSS and will report any issue at Haxe compilation time. This can be done by calling inside a macro:


Or my adding to your Haxe compilation parameters :

--macro domkit.Macros.checkCSS('res/style.css')

Please note that since each CSS property can be used by different components in different ways, and since you can't always tell by CSS rules on which component type the property will be applied, we only check that the property is valid and the CSS accepted for one of the components that defines it.

Defining custom Components

In order to define custom components, you need to: add @:uiComp("name") metadata implements h2d.domkit.Object (if not already inherited from your superclass) * add @:p for each property you wish to expose to domkit markup/CSS

Here's a small example:

// MyComp.hx

enum CustomStyle {

class MyComp extends h2d.Flow implements h2d.domkit.Object {

    @:p public var style(default,set) : CustomStyle;

    function set_style(s) { = s;
        // ....
        return s;    


It is now possible to use your component from any document SRC by doing the following:

<my style="medium"/>

Components with SRC

It is possible to have a component that also have a SRC. In that case, you need to reference the component name in your SRC root node name so its properties can be applied correctly.

Components resolution

Components are resolved by name by adding Comp to the capitalized component name. For instance <something/> will try to load SomethingComp class from local context.

If you wish to customize this name resolution, you can use an init macro such as:

// add --macro Init.setup() to your HXML / Haxe compilation parameters
class Init {
    public static function setup() {

In the path, the $ character is the capitalized component name. By default "$Comp" is a registered path in Heaps.

Custom CSS parsing

Some properties requires custom parsing. For instance color codes, padding boxes, etc. You can specify which parser method to use by changing @:p metadata in the following way:

// will use parseTile CSS parser method
@:p(tile) public var tile : h2d.Tile;

You can use any identifier that is allowed in the current CSS parser. The default Heaps parser can be found in h2d/domkit/BaseComponents.hx

You can extend this parser with your own custom parser to support additional CSS parsing rules. Here's an example:

class MyParser extends h2d.domkit.BaseComponents.CustomParser {
    public function parseIntValues( value : domkit.CssValue ) : Array<Int> {
        return switch( value ) {
        case VList(vl): [for( v in vl ) parseInt(v)]; // comma separated values
        default: [parseInt(value)]; // single value

And then in your component you need to specify which custom parser to use:

@:uiComp("my") @:parser(MyParser)
class MyComp extends h2d.Flow implements h2d.domkit.Object {
   @:p(intValues) public var values : Array<Int>;

And it means you can now use values this way in attributes or CSS:

<my values="1,2,3"/>

Domkit Markup Reference

Domkit markup allows the following syntaxes.

<node attr="value"/>

A component with a CSS attribute value. Please note that the value has to be valid CSS and is parsed then interpreted based on the components custom parsing rules in order to be translated to the actual runtime value for the corresponding node property.

<node attr={expr}/>

Set the attribute based on an Haxe code expression. Unlike previous syntax, here the expression must directly evaluates to the property runtime value, without going through CSS interpretation.

<node attr/>

A shortcut for attr="true". Allows to easily set boolean attributes

<node id="identifier"/>

Creates a field on the current class and set it to the component value upon initialization.

<node id="group[]"/>

Creates an Array of components on the current class and push the component value into it upon initialization.


Allows to pass constructor arguments to your custom component. ATM only Haxe values are allowed to be passed, DomKit does not allow passing CSS values to constructor arguments.

${ for( t in tiles ) <bitmap src={t} id="btns[]"/> }

When using ${..} syntax, you can inject any Haxe code into the markup language, allowing you to add if/for/method calls/etc.

Some Text

This is the equivalent of <text text={"Some Text"}/>, so you can apply CSS to the text components created this way.


When just a Haxe variable identifier is injected into the document content, we assume it contains another component value to be inserted there.




These are markup macros that can be processed in a custom manner by setting domkit.Macros.processMacro in an init macro. It allows you to process identifier path and arguments (Haxe expressions) to return some markup syntax that will be then processed.

Heaps CSS reference

This is the complete documentation for allowed CSS attributes for native Heaps components.


See corresponding heaps documentation

x : 0.5

x position

y : 0.5

y position

alpha : 0.5


rotation : 45

rotation (unlike Heaps, value is expressed in degrees, not radians)

visible : true

toggle visibility

scale : 2.5
scale : 0.5 0.8
scale-x : 0.5
scale-y : 2

Uniform or X/Y scaling

blend : none
blend : alpha (default)
blend : add


Flow properties

These properties are only valid when the object parent is a <flow/> (see corresponding heaps documentation)

margin : 5
margin : 10 20
margin-left : 20
margin-top : 10
margin-bottom : 5
margin-right : 0
margin : 10 20 5 0

Margins around the object (these are FlowProperties.padding values)

align : left
align : top
align : bottom right
halign : right
valign : bottom

Allows to override alignment for a single object in the flow

position : absolute
position : auto

Tells if the object position is automatically set by the flow or manually managed

offset : 10 20
offset-x : 10
offset-y : 20

Offset the object after final position calculus.

min-width: 100
min-height: none

Gives minimal width/height to the object wrt flow calculus.


See corresponding heaps documentation

color : #ff0000
color : #f00

Color tint

smooth : true
smooth : auto

Toggles bilinear filtering or keep auto mode

tile-wrap : true

Enables tile wrapping


See corresponding heaps documentation

src : url("my/tile.png")
src : #f00 20 20

Load the tile or creates one with the specific color and size


See corresponding heaps documentation

text : "some text"

Text content to display

font : url("path/to/bitmapfont.fnt")

Set font to be used for display

letter-spacing : 2

Space between letters

line-spacing : 4

Space between lines

max-width : none
max-width : 300

Maximum width for auto text wrapping

text-align : left
text-align : right
text-align : middle

Alignment of the text (usually not used within a flow, instead use the align property)

text-shadow : 1.5 2 #f00 0.5

Set a drop shadow for the text (dx,dy,color,alpha)

text-color : #f00

Changes text color


See corresponding heaps documentation

width : auto
width : 500
min-width : 450
max-height : none

Set min/max width/height constraints

background : url("my/resource")
background : url("my/resource") 5 8
background : #f00
background : transparent

Flow background with optional borderWidth/Height

debug : true

Display debug lines

vertical : true
horizontal : false

Sets the flow in either display mode

multline : true

Activates multiline

padding : 5
padding : 10 20
padding-left : 20
padding-top : 10
padding-bottom : 5
padding-right : 0
padding : 10 20 5 0

Padding values around contained elements

hspacing : 10
vspacing : 5

Horizontal and vertical spacing between contained elements

content-align : left
content-align : right top
content-valign : middle
content-halign : right

Changes horizontal/vertical default alignment for contained elements (flow horizontalAlign/verticalAlign)