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Video Tutorial: Beginning Core Graphics Part 3: Contexts 1

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In this core graphics video tutorial series you'll learn about drawing contexts and saving context state.

This is a companion discussion topic for the original entry at https://www.raywenderlich.com/3402-beginning-core-graphics/lessons/4
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hey, thanks. this is a very good series so far. I have a question though. When you are adding a clipping path to a context, how does the context know whether all drawing from then on will be inside or outside that path? For example, if you have a square rect of 200 x 200, and you add a clipping path down the center (vertically), will all drawing from then on occur on the right or left side of that line?

If we add an arc path as a clipping path, does all drawing from now on occur inside the path? that is what i think would happen, but what if we instead want all drawing to occur outside?

thanks

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If you do path.addClip() it means that all drawing outside that path is excluded.

If you have a straight line, i.e. not a closed shape, I’m not sure what it does. It didn’t seem to draw anything when I tried. But I wouldn’t do that anyway as it doesn’t make sense.

So create a closed path. Adding a clip means that drawing is done inside that path.

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Is it necessary to begin and end the context in the class funcs in DrawIcon? Those funcs are returning a UIBezierPath so I don’t understand the need to use contexts. Thanks!

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That’s a really good catch - of course there’s no need for a context because no actual drawing is taking place.

Thanks for pointing that out!