Panning and zooming

VisuallyJs has the smoothest pan/zoom for miles around, and exposes a number of hooks for you to inject your own behaviour.

By default, the UI is setup to support an infinite canvas. This means the canvas element is positioned absolute, we set overflow:hidden on the container element (which disables the browser's scrolling mechanism), and the transform origin for the canvas is set to wherever the user last used the mouse or performed a pinch to zoom.

Panning

In the default configuration, panning is performed by dragging the canvas with the mouse, or via touch, and more often than not you won't need to provide any pan options at all. If you want to, though, you can configure pan options via the pan property:

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  pan: {
    axis: "x",
    useMetaKey: true
  }
}
</script>

<SurfaceComponent {renderOptions}/>

Auto pan

The default behaviour of the UI is to automatically pan the canvas whenever a vertex is dragged out of the viewport. We're mentioning it here as it is related to pan, but this is controlled in the vertex drag options.

For more information see this page.

Filtering Panning

It's a fairly common use case that there be some set of elements in your canvas on which a drag should not cause a pan to occur. To handle this, the surface's pan options has the filter parameter. This is a function from which you should return true if you would like a pan to begin. You must return boolean true from this function in order for panning to be enabled.

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  pan: {
    filter: (eventTarget:BrowserElement) => {
    return someLogic(eventTarget);
  }
  }
}
</script>

<SurfaceComponent {renderOptions}/>

Pan Axis

The surface will pan in both the horizontal and vertical axes by default, as you might expect! But you can instruct the surface to pan only in one direction, should you wish to, via the axis property:

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  pan: {
    axis: "x"
  }
}
</script>

<SurfaceComponent {renderOptions}/>

Valid values are x, y and both (which is the default).

Panning with wheel

If you want to use the wheel for panning rather than zooming, you can:

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  pan: {
    wheel: true
  }
}
</script>

<SurfaceComponent {renderOptions}/>

Pan Options

PanOptions

Options to control how a user pans the canvas.

Name	Type	Description
axis?	PanAxis	Optional axes in which to constrain pan - 'x', 'y' or 'both'. Defaults to 'both'.
enabled?	boolean	Defaults to true, meaning panning is enabled.
filter?	(el:Element) => boolean	Optional function which is called at the start of panning and can return false to reject pan starting.
useMetaKey?	boolean	Optional, defaults to false. When true, the user must hold down the meta key (ctrl on windows) in order to pan.
wheel?	boolean	Defaults to false, meaning panning works via canvas drag. If you set this to true, the mousewheel (or move events on a touchpad) will pan the canvas. This will also override any zoom wheel flag.

Zooming

The canvas supports zooming both programmatically and via the mouse wheel (or pinch, on touch devices or a trackpad). A Surface has an associated zoom range, which is the minimum and maximum zoom that can be applied. When using the mouse wheel or pinch, these limits are applied automatically. If you attempt to set a zoom value outside of the zoom range programmatically (via setZoom), the zoom value will be clamped to the current range.

Zooming is configured via the zoom property.

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  zoom: {
    range: [
      0.1,
      5
    ],
    step: 0.1
  }
}
</script>

<SurfaceComponent {renderOptions}/>

Zoom options

ZoomOptions

Options to control how a user manages zoom on the canvas.

Name	Type	Description
fixedTransformOrigin?	PointXY	Optional fixed transform origin for the canvas. Defaults to null.When this is supplied the zoom function does not change the transform origin You can still zoom and pan but the zoom/pan is applied relative to the top/left corner of the content.
initialValue?	number	Initial zoom value. Defaults to 1.
range?	ZoomRange	Zoom range to support. The default is [0.05, 3]
step?	number	When zooming by step, this defines the change in zoom for each step. Defaults to 0.25.
wheel?	boolean	When true - which is the default - the wheel will be used for zoom.

Wheel

You configure whether the wheel manages pan or zoom inside the pan and zoom options. To configure the wheel's behaviour, use the wheel section of the render options.

Filtering wheel events

If you want to control what parts of your UI respond to wheel events, you can do that in one of two ways.

CSS Filter

cssFilter lets you provide a CSS3 selector identifying elements that should not fire wheel events.

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  wheel: {
    cssFilter: ".someElementClass"
  }
}
</script>

<SurfaceComponent {renderOptions}/>

Filter

If you need more fine-grained control than just specifying a CSS selector, filter lets you provide a function which can determine whether or not a wheel event should fire.

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  wheel: {
    filter: (e:MouseEvent) => { return someLogic(e) }
  }
}
</script>

<SurfaceComponent {renderOptions}/>

Meta key

By default, wheel events fire whenever the wheel is manipulated. If you wish, you can tell VisuallyJs only to respond to wheel events when the "meta" key (Ctrl on Windows/Linux, CMD on Mac) is pressed:

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  wheel: {
    useMetaKey: true
  }
}
</script>

<SurfaceComponent {renderOptions}/>

Wheel direction

By default, wheel up zooms in and wheel down zooms out. If you want to switch that, set reverse:true, and then wheel up zooms out, and wheel down zooms in.

<script>
  import { SurfaceComponent } from "@visuallyjs/browser-ui-svelte"
  const renderOptions = {
  wheel: {
    reverse: true
  }
}
</script>

<SurfaceComponent {renderOptions}/>

The full list of wheel options is:

WheelOptions

Options for how to respond to wheel events.

Name	Type	Description
cssFilter?	string	Optional CSS 3 selector to check if the wheel should be enabled for the current event target.
filter?	(e:MouseEvent) => boolean	Optional function to call to check if wheel zooming should be enabled for the current event target.
reverse?	boolean	Defaults to false. If true, the zoom direction is reversed: wheel up zooms out, and wheel down zooms in.
sensitivity?	number	How sensitive the wheel should be.
shiftToChangeMode?	boolean	Defaults to true. When true, holding the SHIFT key while using the mouse wheel will toggle the wheel's mode: if the wheel is currently set to pan, it will zoom. If it is currently set to zoom, it will pan.
useMetaKey?	boolean	If true, the "meta" key (CMD on Mac, Ctrl on windows/linux) must be pressed in order for wheel zoom to operate. This can be useful if your UI fills the screen in one or more axes and your users would not be able to scroll past the Surface widget.

Note that if you set wheel: true in panOptions, the mouse wheel will pan the canvas, and this will take precedence over any zoom wheel configuration.

Panning​

Filtering Panning​

Pan Axis​

Panning with wheel​

Pan Options​

Zooming​

Zoom options​

Wheel​

Filtering wheel events​

CSS Filter​

Filter​

Meta key​

Wheel direction​