Current context when not in drawRect:

Subject: Current context when not in drawRect:
From: Duncan McGregor <email@hidden>
Date: Wed, 22 Apr 2009 10:02:45 +0100
Delivered-to: email@hidden
Delivered-to: email@hidden

Hi

I'm sure this must have come up, but I'm having trouble phrasing the question for Google, so I'd really appreciate some pointers.

I'm writing various functions at the moment that render pdf or images on the command-line. It's RubyCocoa, but the gist is code like

pdf_context = CGPDFContextCreateWithURL(pdf_url, rect, nil)

CGPDFContextBeginPage(pdf_context, nil)
CGContextDrawImage(pdf_context, rect, image)

Now I'd like to be able to use, for example, NSAttributedString to paint text

aString = NSAttributedString.alloc.initWithString("Hello World")
aString.drawInRect(CGRectMake(100, 100, 100, 100))

If I do this, then all hell breaks loose, viz:

Wed Apr 22 09:48:09 Longjohn-2.local ruby[74313] <Error>: CGContextSetFillColorWithColor: invalid context Wed Apr 22 09:48:09 Longjohn-2.local ruby[74313] <Error>: CGContextSetStrokeColorWithColor: invalid context ... Wed Apr 22 09:48:09 Longjohn-2.local ruby[74313] <Error>: CGContextShowGlyphsWithAdvances: invalid context

I'm guessing that somewhere upstream of drawRect: in NSView et al, something sets a thread-local CGContext for NSAttributedString, NSImage etc to catch hold of when they want to draw. So how can I set my pdf_context for them to see?

Or have I got this completely wrong?

Thanks in anticipation

Duncan McGregor
www.VelOCRaptor.com - Simple Mac OCR

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