From ce5646492362c45de276450e6288041cca63b379 Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Mon, 8 Jun 2020 23:47:40 +0200
Subject: [PATCH] widget,gesture: fade out cancelled inkwells

While here, adjust inkwell sizes to match gtx.Constraints.Min.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 gesture/gesture.go        |  4 ++++
 widget/bool.go            |  5 ++++-
 widget/button.go          | 20 +++++++++++++++-----
 widget/material/button.go | 38 ++++++++++++++++++++++++++++----------
 widget/material/switch.go |  4 +++-
 5 files changed, 54 insertions(+), 17 deletions(-)

diff --git a/gesture/gesture.go b/gesture/gesture.go
index 13774419..c6a0599f 100644
--- a/gesture/gesture.go
+++ b/gesture/gesture.go
@@ -147,6 +147,8 @@ func (c *Click) Events(q event.Queue) []ClickEvent {
 				}
 				c.clickedAt = e.Time
 				events = append(events, ClickEvent{Type: TypeClick, Position: e.Position, Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks})
+			} else {
+				events = append(events, ClickEvent{Type: TypeCancel})
 			}
 		case pointer.Cancel:
 			wasPressed := c.state == StatePressed
@@ -304,6 +306,8 @@ func (ct ClickType) String() string {
 		return "TypePress"
 	case TypeClick:
 		return "TypeClick"
+	case TypeCancel:
+		return "TypeCancel"
 	default:
 		panic("invalid ClickType")
 	}
diff --git a/widget/bool.go b/widget/bool.go
index f2f0cc6d..9b37dda3 100644
--- a/widget/bool.go
+++ b/widget/bool.go
@@ -2,6 +2,7 @@ package widget
 
 import (
 	"image"
+	"time"
 
 	"gioui.org/gesture"
 	"gioui.org/io/pointer"
@@ -31,8 +32,10 @@ func (b *Bool) Layout(gtx layout.Context) layout.Dimensions {
 	for _, e := range b.gesture.Events(gtx) {
 		switch e.Type {
 		case gesture.TypeClick:
+			now := gtx.Now()
 			b.Last = Press{
-				Time:     gtx.Now(),
+				Start:    now,
+				End:      now.Add(time.Second),
 				Position: e.Position,
 			}
 			b.Value = !b.Value
diff --git a/widget/button.go b/widget/button.go
index 2d739ea4..08591a4f 100644
--- a/widget/button.go
+++ b/widget/button.go
@@ -33,8 +33,13 @@ type Click struct {
 
 // Press represents a past pointer press.
 type Press struct {
+	// Position of the press.
 	Position f32.Point
-	Time     time.Time
+	// Start is when the press began.
+	Start time.Time
+	// End is when the press was ended by a release or cancel.
+	// A zero End means it hasn't ended yet.
+	End time.Time
 }
 
 // Clicked reports whether there are pending clicks as would be
@@ -73,7 +78,7 @@ func (b *Clickable) Layout(gtx layout.Context) layout.Dimensions {
 	stack.Pop()
 	for len(b.history) > 0 {
 		c := b.history[0]
-		if gtx.Now().Sub(c.Time) < 1*time.Second {
+		if c.End.IsZero() || gtx.Now().Sub(c.Start) < 1*time.Second {
 			break
 		}
 		n := copy(b.history, b.history[1:])
@@ -91,17 +96,22 @@ func (b *Clickable) update(gtx layout.Context) {
 
 	for _, e := range b.click.Events(gtx) {
 		switch e.Type {
-		case gesture.TypeCancel:
-			b.history = nil
 		case gesture.TypeClick:
 			b.clicks = append(b.clicks, Click{
 				Modifiers: e.Modifiers,
 				NumClicks: e.NumClicks,
 			})
+			fallthrough
+		case gesture.TypeCancel:
+			for i := range b.history {
+				if b.history[i].End.IsZero() {
+					b.history[i].End = gtx.Now()
+				}
+			}
 		case gesture.TypePress:
 			b.history = append(b.history, Press{
 				Position: e.Position,
-				Time:     gtx.Now(),
+				Start:    gtx.Now(),
 			})
 		}
 	}
diff --git a/widget/material/button.go b/widget/material/button.go
index b1598a85..33daf45c 100644
--- a/widget/material/button.go
+++ b/widget/material/button.go
@@ -5,6 +5,7 @@ package material
 import (
 	"image"
 	"image/color"
+	"math"
 
 	"gioui.org/f32"
 	"gioui.org/io/pointer"
@@ -190,20 +191,37 @@ func (b IconButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
 
 func drawInk(gtx layout.Context, c widget.Press) {
 	now := gtx.Now()
-	age := now.Sub(c.Time)
+	age := now.Sub(c.Start)
 	t := float32(age.Seconds())
-	const duration = 0.5
-	if t > duration {
-		// Too old.
-		return
-	}
+	const duration = 0.4
 	t = t / duration
+	if t > 1.0 {
+		if c.Start.IsZero() || !c.End.IsZero() {
+			// Too old.
+			return
+		}
+		t = 1.0
+	}
 	defer op.Push(gtx.Ops).Pop()
-	size := float32(gtx.Px(unit.Dp(700))) * t
-	rr := size * .5
-	col := byte(0xcc * t * t)
-	ink := paint.ColorOp{Color: color.RGBA{A: col, R: col, G: col, B: col}}
+	t2 := t
+	if t2 > 1.0 {
+		t2 = 2.0 - t2
+	}
+	bezierBlend := t2 * t2 * (3.0 - 2.0*t2)
+	size := float32(gtx.Constraints.Min.X)
+	if h := float32(gtx.Constraints.Min.Y); h > size {
+		size = h
+	}
+	// Cover the entire constraints min rectangle.
+	size *= 2 * float32(math.Sqrt(2))
+	// Animate.
+	size *= bezierBlend
+	alpha := 0.7 * bezierBlend
+	const col = 0.8
+	ba, bc := byte(alpha*0xff), byte(alpha*col*0xff)
+	ink := paint.ColorOp{Color: color.RGBA{A: ba, R: bc, G: bc, B: bc}}
 	ink.Add(gtx.Ops)
+	rr := size * .5
 	op.TransformOp{}.Offset(c.Position).Offset(f32.Point{
 		X: -rr,
 		Y: -rr,
diff --git a/widget/material/switch.go b/widget/material/switch.go
index bc71e6a8..45b38fe4 100644
--- a/widget/material/switch.go
+++ b/widget/material/switch.go
@@ -91,6 +91,8 @@ func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
 		},
 		NE: rr, NW: rr, SE: rr, SW: rr,
 	}.Op(gtx.Ops).Add(gtx.Ops)
+	dims := image.Point{X: trackWidth, Y: thumbSize}
+	gtx.Constraints.Min = dims
 	drawInk(gtx, s.Switch.Last)
 	stack.Pop()
 
@@ -108,7 +110,7 @@ func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
 	s.Switch.Layout(gtx)
 	stack.Pop()
 
-	return layout.Dimensions{Size: image.Point{X: trackWidth, Y: thumbSize}}
+	return layout.Dimensions{Size: dims}
 }
 
 func drawDisc(ops *op.Ops, sz float32, col color.RGBA) {