Rect.Intersect(Rect) and Rect.Intersects(Rect) have conflicting behaviour

[btanner]

Rect.Intersect specifically calculates the ZR intersection using inclusive operators:

if t.Min.X >= t.Max.X || t.Min.Y >= t.Max.Y {
		return ZR
}

Rect.Intersects uses exclusive operators:

return !(s.Max.X < r.Min.X ||
	s.Min.X > r.Max.X ||
	s.Max.Y < r.Min.Y ||
	s.Min.Y > r.Max.Y)

I think the former is more convenient, because having 2 rectangles with a perfectly aligned edge is has 0 intersection area. I think I would argue that if the area of intersection is 0, intersects should return false.

We can see with a simple example, this behaviour is a bit inconsistent. There are no tests for either right now.

I learned this making a small game with my son, and the overhead of changing and adding tests and creating a PR felt a bit high. But, can do if you need.

Program to repro:

package main

import (
	"fmt"
	"github.com/faiface/pixel"
)

func main() {
	r1 := pixel.R(0, 0, 10, 10)
	r2 := pixel.R(10, 10, 20, 20) 	// No real overlap, just corners touching.
	fmt.Println(r1.Intersect(r2)) 	// Output Rect(0, 0, 0, 0)
	fmt.Println(r1.Intersects(r2)) 	// Output: True
}

[dusk125]

Thanks for bringing this to our attention, this should now be fixed! :) Closing