Fixed cloth constraints issue on mouse highlight

cloth.go

@@ -86,7 +86,7 @@ func (cloth *Cloth) Update(gtx layout.Context, mouse *Mouse, delta float64) {
 	}
 
 	for _, c := range cloth.constraints {
-		if c.isSelected {
+		if c.p1.isActive {
 			c.Update(gtx, cloth, mouse)
 		}
 	}
@@ -97,7 +97,7 @@ func (cloth *Cloth) Update(gtx layout.Context, mouse *Mouse, delta float64) {
 	// For performance reasons we draw the sticks as a single clip path instead of multiple clips paths.
 	// The performance improvement is considerable compared to the multiple clip paths rendered separately.
 	for _, c := range cloth.constraints {
-		if c.isSelected {
+		if c.p1.isActive {
 			// We are using `clip.Outline` instead of `clip.Stroke` for performance reasons.
 			// But we need to draw the full outline of the stroke.
 			path.MoveTo(f32.Pt(float32(c.p1.x), float32(c.p1.y)))
@@ -121,7 +121,8 @@ func (cloth *Cloth) Update(gtx layout.Context, mouse *Mouse, delta float64) {
 	// because the color used for highlighting the selected area
 	// should be different than the cloth's default color.
 	for _, c := range cloth.constraints {
-		if c.isActive && c.isSelected {
+		if (c.p1.isActive && c.p1.highlighted) &&
+			(c.p2.isActive && c.p2.highlighted) {
 			path.Begin(gtx.Ops)
 
 			path.MoveTo(f32.Pt(float32(c.p1.x), float32(c.p1.y)))
@@ -140,8 +141,6 @@ func (cloth *Cloth) Update(gtx layout.Context, mouse *Mouse, delta float64) {
 			paint.FillShape(gtx.Ops, c.color, clip.Outline{
 				Path: path.End(),
 			}.Op())
-
-			c.isActive = false
 		}
 	}
 }

constraint.go

@@ -8,25 +8,21 @@ import (
 )
 
 type Constraint struct {
-	p1, p2     *Particle
-	length     float64
-	isSelected bool
-	isActive   bool
-	color      color.NRGBA
+	p1, p2 *Particle
+	length float64
+	color  color.NRGBA
 }
 
 // NewConstraint creates a new constraint between two points/particles.
 // The constraint actually is a stick which connects two points.
 func NewConstraint(p1, p2 *Particle, length float64, col color.NRGBA) *Constraint {
 	return &Constraint{
-		p1, p2, length, true, false, col,
+		p1, p2, length, col,
 	}
 }
 
 // Update updates the stick between two points by resolving the constraints between them.
 func (c *Constraint) Update(gtx layout.Context, cloth *Cloth, mouse *Mouse) {
-	c.p1.constraint = c
-
 	dx := c.p1.x - c.p2.x
 	dy := c.p1.y - c.p2.y
 	dist := math.Sqrt(dx*dx + dy*dy)
@@ -38,7 +34,7 @@ func (c *Constraint) Update(gtx layout.Context, cloth *Cloth, mouse *Mouse) {
 	// The threshold is the distance between the two points.
 	if mouse.getDragging() {
 		if dist > 150 {
-			c.p1.removeConstraint(cloth)
+			c.removeConstraint(cloth)
 		}
 	}
 
@@ -56,3 +52,13 @@ func (c *Constraint) Update(gtx layout.Context, cloth *Cloth, mouse *Mouse) {
 		c.p2.y -= offsetY
 	}
 }
+
+// removeConstraint removes a specific constraint (stick) from the collection, stored into a slice.
+func (c *Constraint) removeConstraint(cloth *Cloth) {
+	for idx, constraint := range cloth.constraints {
+		if c == constraint {
+			cloth.constraints = append(cloth.constraints[:idx], cloth.constraints[idx+1:]...)
+			break
+		}
+	}
+}

particle.go

@@ -14,7 +14,7 @@ const (
 	clothTearDist  = 60
 	clothPinDist   = 4
 	gravityForce   = 600
-	defFocusArea   = 40
+	defFocusArea   = 50
 	minFocusArea   = 30
 	maxFocusArea   = 150
 	mouseDragForce = 4.2
@@ -23,22 +23,25 @@ const (
 
 // Particle holds the basic components of the particle system.
 type Particle struct {
-	x, y       float64
-	px, py     float64
-	vx, vy     float64
-	friction   float64
-	elasticity float64
-	dragForce  float64
-	pinX       bool
-	color      color.NRGBA
-	constraint *Constraint
+	x, y        float64
+	px, py      float64
+	vx, vy      float64
+	friction    float64
+	elasticity  float64
+	dragForce   float64
+	pinX        bool
+	isActive    bool
+	highlighted bool
+	color       color.NRGBA
 }
 
 // NewParticle initializes a new Particle.
 func NewParticle(x, y float64, col color.NRGBA) *Particle {
 	p := &Particle{
 		x: x, y: y, px: x, py: y, color: col,
 	}
+	p.isActive = true
+	p.highlighted = false
 	p.elasticity = 25.0
 	p.dragForce = mouseDragForce
 
@@ -77,6 +80,8 @@ func (p *Particle) draw(gtx layout.Context, x, y, r float32) {
 
 // update is an internal method to update the cloth system using Verlet integration.
 func (p *Particle) update(gtx layout.Context, mouse *Mouse, dt float64) {
+	p.highlighted = false
+
 	if p.pinX {
 		return
 	}
@@ -120,14 +125,14 @@ func (p *Particle) update(gtx layout.Context, mouse *Mouse, dt float64) {
 		focusArea = minFocusArea
 	}
 
-	if p.constraint != nil && dist < float64(focusArea) {
-		p.constraint.isActive = true
+	if dist < float64(focusArea) {
+		p.highlighted = true
 	}
 
 	// With right click we can tear up the cloth at the mouse position.
 	if mouse.getRightButton() {
-		if p.constraint != nil && dist < float64(focusArea) {
-			p.constraint.isSelected = false
+		if dist < float64(focusArea) {
+			p.isActive = false
 		}
 	}
 
@@ -172,16 +177,6 @@ func (p *Particle) update(gtx layout.Context, mouse *Mouse, dt float64) {
 	p.vx, p.vy = 0.0, 0.0
 }
 
-// removeConstraint removes a specific constraint (stick) from the collection, stored into a slice.
-func (p *Particle) removeConstraint(cloth *Cloth) {
-	for idx, c := range cloth.constraints {
-		if c == p.constraint {
-			cloth.constraints = append(cloth.constraints[:idx], cloth.constraints[idx+1:]...)
-			break
-		}
-	}
-}
-
 // increaseForce increases the dragging force.
 func (p *Particle) increaseForce(m *Mouse) {
 	p.dragForce += m.force