QLThumbnailRequestCreateContext(_:_:_:_:)

Creates a graphics context to draw the thumbnail in.

Declaration

func QLThumbnailRequestCreateContext(_ thumbnail: QLThumbnailRequest!, _ size: CGSize, _ isBitmap: Bool, _ properties: CFDictionary!) -> Unmanaged<CGContext>!

Parameters

size:
The size of the thumbnail; if isBitmap is true the size is in pixels, otherwise it’s in points.
isBitmap:
true if the thumbnail data is bitmap-based, false if vector-based. This value of this parameter affects the interpretation of the size parameter.
properties:
A dictionary containing properties for the thumbnail response. For macOS 10.5, no properties have been defined.

Return Value

A Core Graphics graphics-context object that you can draw your thumbnail image in. You should explicitly release this object when it is no longer needed.

Discussion

You can directly draw your thumbnail data in the graphics-context object created by this function. After calling this function, you should flush the context with QLThumbnailRequestFlushContext(_:_:). Also be sure to release the CGContext object.

With this function you can create two types of graphics contexts for drawing thumbnails: bitmap and single-page vector-based; you use the isBitmap flag to distinguish between the two. Quick Look handles bitmap thumbnail context differently than non-bitmap contexts; in the latter case, Quick Look might scale the drawing up or down if necessary, and it respects the scale factor (for HiDPI support).

If you prefer to work in Objective-C code, you can convert the created CGContext to a NSGraphicsContext object using init(graphicsPort:flipped:).

Special Considerations

Thread-safety: This function should be called in the same thread as the thumbnail request is made in; generally, this is the same thread in which the GenerateThumbnailForURL callback was invoked.