Draw9patch tool, what for i should use red border, marked by pressing ctrl

Question

In official documentation i didn't find answer. I can set border of image that indicates areas which will be stretched, but when i press ctrl key, color of border became red, and i don't understand what for it is. It looks like

Answer 1

This might be helpful: https://stackoverflow.com/a/11854891/1234007

Btw, this red is documented in 4.3 documentation as optical bound. Read about it here http://developer.android.com/about/versions/android-4.3.html#Graphics

Answer 2

Take a look at this thread and there's some discussion about it:

Android 9 Patch tool: What is the new layout bounds feature?

Something about layout bounds that are not used by the Framework.

I've used 9-patch images plenty but honestly never noticed these before. Interesting!

Answer 3

For more references about a bug introduced with gradle 0.9.1, please see my answer: https://stackoverflow.com/a/22580228/1345391