Dealing with exceptions in a drawing stack
Dealing with exceptions in a drawing stack
- Subject: Dealing with exceptions in a drawing stack
- From: Graham Cox <email@hidden>
- Date: Thu, 15 Jan 2009 15:34:34 +1100
Suppose I have a drawing stack that is called from a view's drawRect:
method. This stack can end up quite deep, with objects calling other
objects to implement parts of their drawing. Some of these methods
will save and restore the graphics context.
If an exception is thrown from somewhere down inside this stack, I'd
prefer it if I could continue to draw what can be drawn, rather than
have to abort the drawing altogether which usually leaves the whole
view in a weird state (at which point I'm hosed - I have to abandon
that document and create a new one, which is hardly user friendly).
Short of using try/catch around every place where the graphics context
is saved and restored, is there a way to unwind the graphics context
stack or at least put it into a good known state? (i.e. discard all
the saved states and start over). If so, I can then implement a try/
catch at a higher level and fix up the graphics context there.
Anyone had some experience of handling this?
--Graham
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