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[3.0.0] Interfaces supported by the plug-in

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List of interfaces supported/implemented by the plug-in in VST 3.0.0

Vst:: IComponent

Component base interface.

  • [plug imp]
  • [released: 3.0.0]
  • [mandatory]

This is the basic interface for a VST component and must always be supported. It contains the common parts of any kind of processing class. The parts that are specific to a media type are defined in a separate interface. An implementation component must provide both the specific interface and Vst:: IComponent.

See also Steinberg:: IPluginBase.

Vst:: IAudioProcessor

Audio processing interface.

This interface must always be supported by audio processing plug-ins.

Vst:: IEditController

Edit controller component interface.

  • [plug imp]
  • [released: 3.0.0]
  • [mandatory]

The controller part of an effect or instrument with parameter handling (export, definition, conversion...).

See also Vst:: IComponent::getControllerClassId, Vst:: IMidiMapping.

Vst:: IConnectionPoint

Connect a component with another one.

  • [plug imp]
  • [host imp]
  • [released: 3.0.0]
  • [mandatory]

This interface is used for the communication of separate components. Note that some hosts will place a proxy object between the components so that they are not directly connected.

See also Communication between the components.

Vst:: IUnitInfo

Edit controller extension to describe the plug-in structure.

Vst:: IUnitInfo describes the internal structure of the plug-in.

  • The root unit is the component itself, so getUnitCount must return 1 at least.
  • The root unit id has to be 0 (kRootUnitId).
  • Each unit can reference one program list - this reference must not change.
  • Each unit that uses a program list references one program of the list.

See also VST 3 Units, Vst:: IUnitHandler.

Vst:: IProgramListData

Component extension to access program list data.

A component can support program list data via this interface or/and unit preset data (Vst:: IUnitData).

See also Vst:: IUnitData, Complex Plug-in Structures / Multi-timbral Instruments.

Vst:: IUnitData

Component extension to access unit data.

A component can support unit preset data via this interface or program list data (Vst:: IProgramListData).

See also Presets & Program Lists.

Steinberg:: IPlugView

Plug-in definition of a view.

  • [plug imp]
  • [released: 3.0.0]

Sizing of a view

After the creation of a IPlugView, the plug-in must make sure that it returns the correct size if the host asks for it (IPlugView::getSize ()).

Usually, the size of a plug-in view is fixed. But both the host and the plug-in can cause a view to be resized:

  • Host: If IPlugView::canResize () returns kResultTrue, the host will set up the window so that the user can resize it. While the user resizes the window, IPlugView::checkSizeConstraint () is called, allowing the plug-in to change the size to a valid supported rectangle size. The host then resizes the window to this rect and has to call IPlugView::onSize ().

  • Plug-in: The plug-in can call IPlugFrame::resizeView () and cause the host to resize the window. Afterwards, in the same callstack, the host has to call IPlugView::onSize () if a resize is needed (size was changed).

ⓘ Note
Note that if the host calls IPlugView::getSize () before calling IPlugView::onSize () (if needed), it will get the old size, not the current one!

Here the calling sequence:

  • plug-in->host: IPlugFrame::resizeView (newSize)
  • host->plug-in (optional): IPlugView::getSize () returns the currentSize (not the newSize!)
  • host->plug-in: if newSize is different from the current size: IPlugView::onSize (newSize)
  • host->plug-in (optional): IPlugView::getSize () returns the newSize

ⓘ Note
Please only resize the platform representation of the view when Steinberg:: IPlugView::onSize() is called.

Keyboard handling

The plug-in view receives keyboard events from the host. A view implementation must not handle keyboard events by the means of platform callbacks, but let the host pass them to the view. The host depends on a proper return value when Steinberg:: IPlugView::onKeyDown is called, otherwise the plug-in view may cause a malfunction of the host's key command handling.

See also Steinberg:: IPlugFrame, Platform UI Types.