How can I define lines so when I click on the screen, my program knows whether I clicked on A B or C?
this post was submitted on 13 Jan 2025
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My approach would involve using some kind of polygon library. When you draw lines, you're really defining polygons within your canvas. In the case of regions B and C, the edge of the screen make up the rest of the polygon.
Once you have your polygons defined, you can compare the coordinates of the click event to the polygons. With a good library, it should be fairly trivial to check if a point is within a polygon.
In the case of region A, you'd find that a click is inside both region A and region B, so I guess I'd also check to see if there are multiple polygons a click could be inside. If there are, then you need to also see if a polygon is inside another polygon to determine the specific polygon clicked. This is also made much simpler by using a good library
I do want to mention this is a rabbit hole, as a U shaped polygon can be tricky to check. so I strongly suggest using a library for checking point in polygon.