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Creating Viz Ops

Viz Ops can be used to easily visualize things in the patchfield.

You can use the canvas drawing API to draw things in the patchfield.

There is quite a variety of Viz Ops in cables already, take a look

To make any of your ops a Viz Ops, you have to implement the function renderVizLayer:


  • ctx is the 2d drawing context
  • layer contains information about the current op size, scale and positioning. For example:
op.renderVizLayer = (ctx, layer) =>

If exists, this function will be called whenever an update is needed.

Properties of layer:

x,y is your topleft corner where you start drawing.
width,height is the size of the canvas of your op.


Have a look at this example op: Ops.Templates.ExampleVizOp

const inNum = op.inFloat("Number", 23);
op.setUiAttrib({ "height": 200, "width": 200, "resizable": true });

op.renderVizLayer = (ctx, layer) =>
    // clear the canvas in a dark grey color
    ctx.fillStyle = "#222";
        layer.x, layer.y,
        layer.width, layer.height);

    const padding = 10;

    ctx.fillStyle = "#05f";

    // draw a circle with a radius of the height of our op canvas
    let circle = new Path2D();
    circle.arc(layer.x + layer.height / 2, layer.y + layer.height / 2, layer.height/2, 0, 2 * Math.PI, false);
    // draw text, use layer height for fontsize, so it is fixed when resizing the op or zooming the patch
    ctx.fillStyle = "#fff";
    const fontSize = layer.height * 0.7;
    ctx.font = "normal " + fontSize + "px sourceCodePro";
    ctx.fillText(Math.round(inNum.get() * 10000) / 10000, layer.x + padding, layer.y + fontSize);
    // this text will not scale and be at fixed size when zooming in/out
    ctx.font = "normal " + 12 + "px sourceCodePro";
    ctx.fillText(Math.round(inNum.get() * 10000) / 10000, layer.x + padding, layer.y+20);


For more information on how to write your own ops, start with this part of the docs.

help cables get better and edit this file on github