nsITaskbarPreviewController

nsITaskbarPreviewController provides the behavior for the taskbar previews.
Its methods and properties are used by nsITaskbarPreview. Clients are
intended to provide their own implementation of this interface. Depending on
the interface the controller is attached to, only certain methods/attributes
are required to be implemented.

Methods

drawPreview(ctx)

Invoked by nsITaskbarPreview when it needs to render the preview. The
context is attached to a surface with the controller’s width and height
which are obtained immediately before the call.

Note that the context is not attached to a canvas element.

Parameters

ctx	Canvas drawing context

drawThumbnail(ctx, width, height)

Invoked by the taskbar preview when it needs to draw the thumbnail in the
taskbar’s application preview window.

Note: it is guaranteed that width/height == thumbnailAspectRatio
(modulo rounding errors)

Also note that the context is not attached to a canvas element.

Parameters

ctx	Canvas drawing context
width	The width of the surface backing the drawing context
height	The height of the surface backing the drawing context

onClose()

Invoked when the user presses the close button on the tab preview.

onActivate()

Invoked when the user clicks on the tab preview.

Returns

true if the top level window corresponding to the preview should be activated, false if activation is not accepted.

onClick(button)

Invoked when one of the buttons on the window preview’s toolbar is pressed.

Parameters

button

The button that was pressed. This can be compared with the buttons returned by nsITaskbarWindowPreview.getButton.

Attributes

width

The width of the preview image. This value is allowed to change at any
time. See drawPreview for more information.

height

The height of the preview image. This value is allowed to change at any
time. See drawPreview for more information.

thumbnailAspectRatio

The aspect ratio of the thumbnail - this does not need to match the ratio
of the preview. This value is allowed to change at any time. See
drawThumbnail for more information.