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I'm having a problem I don't understand. I'm developing an OpenGL app for iOS. Because at some points I want to force the orientation of the view programatically, and Apple for whatever reason doesn't make it easy (or even possible), I'm doing it by hand.

I return always NO in shouldAutoRotateToInterfaceOrientation, and when I want to change the orientation (to portrait, for example), I do something like this in the UIView:

[self setTransform:CGAffineTransformMake(1, 0, 0, 1, 0, 0)];
[self setBounds:CGRectMake(0, 0, 768, 1024)];

This works fine.

In order to support Retina devices, I started checking [UIScreen mainScreen].scale, and setting self.contentScaleFactor accordingly. I also modified the code above to account for the new dimensions, like this:

[self setTransform:CGAffineTransformMake(1, 0, 0, 1, 0, 0)];
[self setBounds:CGRectMake(0, 0, 2*768, 2*1024)];

Same rotation, different size. The weird result with this is that I get a "screen" with the right size, but offsetted half a screen to the bottom and the left. To correct for this, I need to do the following:

[self setTransform:CGAffineTransformMake(1, 0, 0, 1, 0, 0)];
[self setBounds:CGRectMake(-768, -1024, 2*768 - 768, 2*1024 - 1024)];

This works, but it's ugly, I also need to make similar corrections when I get touch coordinates, and worst of all, I don't understand what's going on or why the above "correction" works.

Can anyone shed some light on this issue?

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Don't hard-code screen size values!

If you get screen size values from [[UIScreen mainScreen] bounds]:

  • Take the status bar height into account.
  • If portrait: set width to screen height and height to screen width

    -- Look at my code to see what I'm talking about: UIScreen+Flexible category.

If you get screen size values from the parent View:

  • Make sure you aren't setting any frames before the parent view's frame is set.

Also, Use setFrame. I can't think of a case where you should be setting bounds?*

*I may be wrong about bound-setting.

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In OpenGL ES all your transformation need to be make on OpenGL ES context. And on your view layer you need to set scaleFactor on view object which is GLKView type.

view.contentScaleFactor = [UIScreen mainScreen].scale;

And do not forget to set the glViewPort.

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