Creates a graphics context to draw the preview in.
SDK
- macOS 10.0–10.15Deprecated
Framework
- Quick
Look
Declaration
CGContext Ref QLPreviewRequestCreateContext(QLPreview Request Ref preview, CGSize size, Boolean isBitmap, CFDictionary Ref properties);
Parameters
preview
The preview request object.
size
The size of the preview; if
is
isBitmap true
the size is in pixels, otherwise it is in points.isBitmap
true
if the preview uses a bitmap-based graphics context,false
otherwise. This value of this parameter affects the interpretation of thesize
parameter.properties
A dictionary containing properties for the preview response. Preview Properties lists the current property keys and describes their values.
Return Value
A Core Graphics graphics-context object that you can draw your preview image in. You should explicitly release this object when it is no longer needed.
Discussion
You can directly draw your preview data in the graphics-context object created by this function. After calling this function, you should flush the context with QLPreview
. Also be sure to release the CGContext
object.
Quick Look provides three types of graphics contexts for drawing previews: bitmap, single-page vector-based, and multi-page vector-based (for PDF previews). You use this function to acquire a context for bitmap and single-page vector drawing; the is
parameter is used to distinguish between them. For multi-page contexts, use the QLPreview
function.
If you prefer to work in Objective-C code, you can convert the created CGContext
to a NSGraphics
object using graphics
.
Special Considerations
Thread-safety: This function should be called in the same thread as the preview request is made in; generally, this is the same thread in which the GeneratePreviewForURL callback was invoked.