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Re: NSImageView


From: Fred Kiefer
Subject: Re: NSImageView
Date: Mon, 24 Jun 2002 01:33:09 +0200
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; de-DE; rv:0.9.4) Gecko/20011019 Netscape6/6.2

Jeff Teunissen wrote:

Nicola Pero wrote:


We can't change the API, so we probably can't just use a composite
operation in NSImageView, but must do things properly and optimize
properly the image drawing to the clipped area in the backend.


NSImageCells with alpha need to clear their background (or something)
before drawing, otherwise they draw over the tops of themselves, making
the sections with nonzero alpha get progressively opaque.


I am not sure, if you are right. The way this should be handled is different. When a cell does not fill the total background it returns YES from the isOpaque method. Otherwise, and this is the default, NO is returned, which should result in all the views below the NSImageCell to redraw themselves first. If this simple and correct mechnism does not work for the redrawing of NSImageCells, than we have a more general problem with the drawing of all views. Do you have a small program to show this problem?


The same thing happens with antialiased text; text gets drawn over itself,
making it darker and darker the more times it's drawn.


This I have seen myself. This looks like the text is drawn more often than the background is. This is of course an error, but I could not trace down where this happens.







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