How do I determine which triangle did the user touch in this rectangle?

Question

I made an Android custom view that looks like a D-Pad (image below). Given the touched coordinate (x,y), rectangle width (w), and rectangle height (h), ignoring the white diagonal and rounded corners, could somebody help me how do I determine which triangle that the user touch?

Additional info: (0,0) is upper left corner

http://stackoverflow.com/questions/8721406/how-to-determine-if-a-point-is-inside-a-2d-convex-polygon — Paul Abbott, Dec 30 '15 at 22:27
That will work, but it's swatting flies with an F16. Waaay too complicated and slow for this trivial example. — Lee Daniel Crocker, Dec 30 '15 at 23:40

Lee Daniel Crocker · Accepted Answer · 2015-12-31T18:55:40.287

3

Shift the origin to the center: subtract w/2 from x and h/2 from y. If it's not a square (say w is greater than h) then normalize the larger dimension: x *= h; x /= w; Then, the four sections can be determined as follows:

x < 0, |y| < |x| = left
x > 0, |y| < |x| = right
y < 0, |x| < |y| = up
y > 0, |x| < |y| = down

(Any other condition, such as x=y=0, or |x|=|y|, means you're on the diagonals).

edited Dec 31 '15 at 18:55

answered Dec 30 '15 at 23:02

Lee Daniel Crocker

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What if the rectangle is not a square? – גלעד ברקן Dec 31 '15 at 04:52

How do I determine which triangle did the user touch in this rectangle?

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