From 40091c5918910a4d0493a610fc71acc605d5ed3e Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Sun, 11 Aug 2019 18:15:59 +0200
Subject: [PATCH] ui/gesture: add Scroll.State method

And move Click.State to a method.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 ui/gesture/gesture.go | 74 ++++++++++++++++++++++++++++++++-----------
 ui/layout/list.go     |  2 +-
 ui/text/editor.go     |  2 +-
 3 files changed, 57 insertions(+), 21 deletions(-)

diff --git a/ui/gesture/gesture.go b/ui/gesture/gesture.go
index 9bf04427..0ab29582 100644
--- a/ui/gesture/gesture.go
+++ b/ui/gesture/gesture.go
@@ -23,8 +23,8 @@ import (
 // Click detects click gestures in the form
 // of ClickEvents.
 type Click struct {
-	// State tracks the current state
-	State ClickState
+	// state tracks the gesture state.
+	state ClickState
 }
 
 type ClickState uint8
@@ -55,6 +55,8 @@ type Scroll struct {
 	scroll float32
 }
 
+type ScrollState uint8
+
 type flinger struct {
 	// Current offset in pixels.
 	x float32
@@ -72,8 +74,12 @@ const (
 )
 
 const (
+	// StateNormal is the default click state.
 	StateNormal ClickState = iota
+	// StateFocused is reported when a pointer
+	// is hovering over the handler.
 	StateFocused
+	// StatePressed is then a pointer is pressed.
 	StatePressed
 )
 
@@ -86,6 +92,16 @@ const (
 	TypeClick
 )
 
+const (
+	// StateIdle is the default scroll state.
+	StateIdle ScrollState = iota
+	// StateDrag is reported during drag gestures.
+	StateDragging
+	// StateFlinging is reported when a fling is
+	// in progress.
+	StateFlinging
+)
+
 var (
 	touchSlop = ui.Dp(3)
 	// Pixels/second.
@@ -103,6 +119,11 @@ func (c *Click) Add(ops *ui.Ops) {
 	op.Add(ops)
 }
 
+// State reports the click state.
+func (c *Click) State() ClickState {
+	return c.state
+}
+
 // Events reports all click events for the available events.
 func (c *Click) Events(q input.Queue) []ClickEvent {
 	var events []ClickEvent
@@ -113,24 +134,24 @@ func (c *Click) Events(q input.Queue) []ClickEvent {
 		}
 		switch e.Type {
 		case pointer.Release:
-			wasPressed := c.State == StatePressed
-			c.State = StateNormal
+			wasPressed := c.state == StatePressed
+			c.state = StateNormal
 			if wasPressed {
 				events = append(events, ClickEvent{Type: TypeClick, Position: e.Position, Source: e.Source})
 			}
 		case pointer.Cancel:
-			c.State = StateNormal
+			c.state = StateNormal
 		case pointer.Press:
-			if c.State == StatePressed || !e.Hit {
+			if c.state == StatePressed || !e.Hit {
 				break
 			}
-			c.State = StatePressed
+			c.state = StatePressed
 			events = append(events, ClickEvent{Type: TypePress, Position: e.Position, Source: e.Source})
 		case pointer.Move:
-			if c.State == StatePressed && !e.Hit {
-				c.State = StateNormal
-			} else if c.State < StateFocused {
-				c.State = StateFocused
+			if c.state == StatePressed && !e.Hit {
+				c.state = StateNormal
+			} else if c.state < StateFocused {
+				c.state = StateFocused
 			}
 		}
 	}
@@ -151,11 +172,6 @@ func (s *Scroll) Stop() {
 	s.flinger = flinger{}
 }
 
-// Dragging reports whether the user is dragging the Scroll.
-func (s *Scroll) Dragging() bool {
-	return s.dragging
-}
-
 // Scroll detects the scrolling distance from the available events and
 // ongoing fling gestures.
 func (s *Scroll) Scroll(cfg ui.Config, q input.Queue, axis Axis) int {
@@ -243,9 +259,16 @@ func (s *Scroll) val(p f32.Point) float32 {
 	}
 }
 
-// Active reports whether a fling gesture is in progress.
-func (s *Scroll) Active() bool {
-	return s.flinger.Active()
+// State reports the scroll state.
+func (s *Scroll) State() ScrollState {
+	switch {
+	case s.flinger.Active():
+		return StateFlinging
+	case s.dragging:
+		return StateDragging
+	default:
+		return StateIdle
+	}
 }
 
 func (f *flinger) Init(now time.Time, v0 float32) {
@@ -332,3 +355,16 @@ func (cs ClickState) String() string {
 		panic("invalid ClickState")
 	}
 }
+
+func (s ScrollState) String() string {
+	switch s {
+	case StateIdle:
+		return "StateIdle"
+	case StateDragging:
+		return "StateDragging"
+	case StateFlinging:
+		return "StateFlinging"
+	default:
+		panic("unreachable")
+	}
+}
diff --git a/ui/layout/list.go b/ui/layout/list.go
index 3e892301..92a3996e 100644
--- a/ui/layout/list.go
+++ b/ui/layout/list.go
@@ -87,7 +87,7 @@ func (l *List) Init(cfg ui.Config, q input.Queue, ops *ui.Ops, cs Constraints, l
 
 // Dragging reports whether the List is being dragged.
 func (l *List) Dragging() bool {
-	return l.scroll.Dragging()
+	return l.scroll.State() == gesture.StateDragging
 }
 
 func (l *List) update() {
diff --git a/ui/text/editor.go b/ui/text/editor.go
index 139bec31..c9c505e5 100644
--- a/ui/text/editor.go
+++ b/ui/text/editor.go
@@ -105,7 +105,7 @@ func (e *Editor) Next(cfg ui.Config, queue input.Queue) (EditorEvent, bool) {
 				Y: int(math.Round(float64(evt.Position.Y))),
 			})
 			e.requestFocus = true
-			if !e.scroller.Active() {
+			if e.scroller.State() != gesture.StateFlinging {
 				e.scrollToCaret(cfg)
 			}
 		}