# Composition Modes

Composition allows you to draw a shape and blend it with the existing pixels. The canvas supports several composition modes using the `globalCompositeOperation(mode)` operations. For instance:

* `source-over`
* `source-in`
* `source-out`
* `source-atop`

Let's begin with a short example demonstrating the exclusive or composition:

```
onPaint: {
    var ctx = getContext("2d")
    ctx.globalCompositeOperation = "xor"
    ctx.fillStyle = "#33a9ff"

    for(var i=0; i<40; i++) {
        ctx.beginPath()
        ctx.arc(Math.random()*400, Math.random()*200, 20, 0, 2*Math.PI)
        ctx.closePath()
        ctx.fill()
    }
}
```

The example below will demonstrate all composition modes by iterating over them and combining a rectangle and a circle. You can find the resulting output below the source code.

```
property var operation : [
    'source-over', 'source-in', 'source-over',
    'source-atop', 'destination-over', 'destination-in',
    'destination-out', 'destination-atop', 'lighter',
    'copy', 'xor', 'qt-clear', 'qt-destination',
    'qt-multiply', 'qt-screen', 'qt-overlay', 'qt-darken',
    'qt-lighten', 'qt-color-dodge', 'qt-color-burn',
    'qt-hard-light', 'qt-soft-light', 'qt-difference',
    'qt-exclusion'
    ]

onPaint: {
    var ctx = getContext('2d')

    for(var i=0; i<operation.length; i++) {
        var dx = Math.floor(i%6)*100
        var dy = Math.floor(i/6)*100
        ctx.save()
        ctx.fillStyle = '#33a9ff'
        ctx.fillRect(10+dx,10+dy,60,60)
        ctx.globalCompositeOperation = root.operation[i]
        ctx.fillStyle = '#ff33a9'
        ctx.globalAlpha = 0.75
        ctx.beginPath()
        ctx.arc(60+dx, 60+dy, 30, 0, 2*Math.PI)
        ctx.closePath()
        ctx.fill()
        ctx.restore()
    }
}
```

![image](/files/EJcDPbJBClcbrTfGkwDh)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.novaflowos.com/start/qt6-qml-book/readme/ch08-canvas/composition-modes.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.