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gesture.go
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gesture.go
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// SPDX-License-Identifier: Unlicense OR MIT
/*
Package gesture implements common pointer gestures.
Gestures accept low level pointer Events from an event
Queue and detect higher level actions such as clicks
and scrolling.
*/
package gesture
import (
"image"
"math"
"runtime"
"time"
"github.com/kanryu/mado/f32"
"github.com/kanryu/mado/internal/fling"
"github.com/kanryu/mado/io/event"
"github.com/kanryu/mado/io/input"
"github.com/kanryu/mado/io/key"
"github.com/kanryu/mado/io/pointer"
"github.com/kanryu/mado/op"
"github.com/kanryu/mado/unit"
)
// The duration is somewhat arbitrary.
const doubleClickDuration = 200 * time.Millisecond
// Hover detects the hover gesture for a pointer area.
type Hover struct {
// entered tracks whether the pointer is inside the gesture.
entered bool
// pid is the pointer.ID.
pid pointer.ID
}
// Add the gesture to detect hovering over the current pointer area.
func (h *Hover) Add(ops *op.Ops) {
event.Op(ops, h)
}
// Update state and report whether a pointer is inside the area.
func (h *Hover) Update(q input.Source) bool {
for {
ev, ok := q.Event(pointer.Filter{
Target: h,
Kinds: pointer.Enter | pointer.Leave | pointer.Cancel,
})
if !ok {
break
}
e, ok := ev.(pointer.Event)
if !ok {
continue
}
switch e.Kind {
case pointer.Leave, pointer.Cancel:
if h.entered && h.pid == e.PointerID {
h.entered = false
}
case pointer.Enter:
if !h.entered {
h.pid = e.PointerID
}
if h.pid == e.PointerID {
h.entered = true
}
}
}
return h.entered
}
// Click detects click gestures in the form
// of ClickEvents.
type Click struct {
// clickedAt is the timestamp at which
// the last click occurred.
clickedAt time.Duration
// clicks is incremented if successive clicks
// are performed within a fixed duration.
clicks int
// pressed tracks whether the pointer is pressed.
pressed bool
// hovered tracks whether the pointer is inside the gesture.
hovered bool
// entered tracks whether an Enter event has been received.
entered bool
// pid is the pointer.ID.
pid pointer.ID
}
// ClickEvent represent a click action, either a
// KindPress for the beginning of a click or a
// KindClick for a completed click.
type ClickEvent struct {
Kind ClickKind
Position image.Point
Source pointer.Source
Modifiers key.Modifiers
// NumClicks records successive clicks occurring
// within a short duration of each other.
NumClicks int
}
type ClickKind uint8
// Drag detects drag gestures in the form of pointer.Drag events.
type Drag struct {
dragging bool
pressed bool
pid pointer.ID
start f32.Point
}
// Scroll detects scroll gestures and reduces them to
// scroll distances. Scroll recognizes mouse wheel
// movements as well as drag and fling touch gestures.
type Scroll struct {
dragging bool
estimator fling.Extrapolation
flinger fling.Animation
pid pointer.ID
last int
// Leftover scroll.
scroll float32
}
type ScrollState uint8
type Axis uint8
const (
Horizontal Axis = iota
Vertical
Both
)
const (
// KindPress is reported for the first pointer
// press.
KindPress ClickKind = iota
// KindClick is reported when a click action
// is complete.
KindClick
// KindCancel is reported when the gesture is
// cancelled.
KindCancel
)
const (
// StateIdle is the default scroll state.
StateIdle ScrollState = iota
// StateDragging is reported during drag gestures.
StateDragging
// StateFlinging is reported when a fling is
// in progress.
StateFlinging
)
const touchSlop = unit.Dp(3)
// Add the handler to the operation list to receive click events.
func (c *Click) Add(ops *op.Ops) {
event.Op(ops, c)
}
// Hovered returns whether a pointer is inside the area.
func (c *Click) Hovered() bool {
return c.hovered
}
// Pressed returns whether a pointer is pressing.
func (c *Click) Pressed() bool {
return c.pressed
}
// Update state and return the next click events, if any.
func (c *Click) Update(q input.Source) (ClickEvent, bool) {
for {
evt, ok := q.Event(pointer.Filter{
Target: c,
Kinds: pointer.Press | pointer.Release | pointer.Enter | pointer.Leave | pointer.Cancel,
})
if !ok {
break
}
e, ok := evt.(pointer.Event)
if !ok {
continue
}
switch e.Kind {
case pointer.Release:
if !c.pressed || c.pid != e.PointerID {
break
}
c.pressed = false
if !c.entered || c.hovered {
return ClickEvent{
Kind: KindClick,
Position: e.Position.Round(),
Source: e.Source,
Modifiers: e.Modifiers,
NumClicks: c.clicks,
}, true
} else {
return ClickEvent{Kind: KindCancel}, true
}
case pointer.Cancel:
wasPressed := c.pressed
c.pressed = false
c.hovered = false
c.entered = false
if wasPressed {
return ClickEvent{Kind: KindCancel}, true
}
case pointer.Press:
if c.pressed {
break
}
if e.Source == pointer.Mouse && e.Buttons != pointer.ButtonPrimary {
break
}
if !c.hovered {
c.pid = e.PointerID
}
if c.pid != e.PointerID {
break
}
c.pressed = true
if e.Time-c.clickedAt < doubleClickDuration {
c.clicks++
} else {
c.clicks = 1
}
c.clickedAt = e.Time
return ClickEvent{Kind: KindPress, Position: e.Position.Round(), Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks}, true
case pointer.Leave:
if !c.pressed {
c.pid = e.PointerID
}
if c.pid == e.PointerID {
c.hovered = false
}
case pointer.Enter:
if !c.pressed {
c.pid = e.PointerID
}
if c.pid == e.PointerID {
c.hovered = true
c.entered = true
}
}
}
return ClickEvent{}, false
}
func (ClickEvent) ImplementsEvent() {}
// Add the handler to the operation list to receive scroll events.
// The bounds variable refers to the scrolling boundaries
// as defined in [pointer.Filter].
func (s *Scroll) Add(ops *op.Ops) {
event.Op(ops, s)
}
// Stop any remaining fling movement.
func (s *Scroll) Stop() {
s.flinger = fling.Animation{}
}
// Update state and report the scroll distance along axis.
func (s *Scroll) Update(cfg unit.Metric, q input.Source, t time.Time, axis Axis, bounds image.Rectangle) int {
total := 0
f := pointer.Filter{
Target: s,
Kinds: pointer.Press | pointer.Drag | pointer.Release | pointer.Scroll | pointer.Cancel,
ScrollBounds: bounds,
}
for {
evt, ok := q.Event(f)
if !ok {
break
}
e, ok := evt.(pointer.Event)
if !ok {
continue
}
switch e.Kind {
case pointer.Press:
if s.dragging {
break
}
// Only scroll on touch drags, or on Android where mice
// drags also scroll by convention.
if e.Source != pointer.Touch && runtime.GOOS != "android" {
break
}
s.Stop()
s.estimator = fling.Extrapolation{}
v := s.val(axis, e.Position)
s.last = int(math.Round(float64(v)))
s.estimator.Sample(e.Time, v)
s.dragging = true
s.pid = e.PointerID
case pointer.Release:
if s.pid != e.PointerID {
break
}
fling := s.estimator.Estimate()
if slop, d := float32(cfg.Dp(touchSlop)), fling.Distance; d < -slop || d > slop {
s.flinger.Start(cfg, t, fling.Velocity)
}
fallthrough
case pointer.Cancel:
s.dragging = false
case pointer.Scroll:
switch axis {
case Horizontal:
s.scroll += e.Scroll.X
case Vertical:
s.scroll += e.Scroll.Y
}
iscroll := int(s.scroll)
s.scroll -= float32(iscroll)
total += iscroll
case pointer.Drag:
if !s.dragging || s.pid != e.PointerID {
continue
}
val := s.val(axis, e.Position)
s.estimator.Sample(e.Time, val)
v := int(math.Round(float64(val)))
dist := s.last - v
if e.Priority < pointer.Grabbed {
slop := cfg.Dp(touchSlop)
if dist := dist; dist >= slop || -slop >= dist {
q.Execute(pointer.GrabCmd{Tag: s, ID: e.PointerID})
}
} else {
s.last = v
total += dist
}
}
}
total += s.flinger.Tick(t)
if s.flinger.Active() {
q.Execute(op.InvalidateCmd{})
}
return total
}
func (s *Scroll) val(axis Axis, p f32.Point) float32 {
if axis == Horizontal {
return p.X
} else {
return p.Y
}
}
// 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
}
}
// Add the handler to the operation list to receive drag events.
func (d *Drag) Add(ops *op.Ops) {
event.Op(ops, d)
}
// Update state and return the next drag event, if any.
func (d *Drag) Update(cfg unit.Metric, q input.Source, axis Axis) (pointer.Event, bool) {
for {
ev, ok := q.Event(pointer.Filter{
Target: d,
Kinds: pointer.Press | pointer.Drag | pointer.Release | pointer.Cancel,
})
if !ok {
break
}
e, ok := ev.(pointer.Event)
if !ok {
continue
}
switch e.Kind {
case pointer.Press:
if !(e.Buttons == pointer.ButtonPrimary || e.Source == pointer.Touch) {
continue
}
d.pressed = true
if d.dragging {
continue
}
d.dragging = true
d.pid = e.PointerID
d.start = e.Position
case pointer.Drag:
if !d.dragging || e.PointerID != d.pid {
continue
}
switch axis {
case Horizontal:
e.Position.Y = d.start.Y
case Vertical:
e.Position.X = d.start.X
case Both:
// Do nothing
}
if e.Priority < pointer.Grabbed {
diff := e.Position.Sub(d.start)
slop := cfg.Dp(touchSlop)
if diff.X*diff.X+diff.Y*diff.Y > float32(slop*slop) {
q.Execute(pointer.GrabCmd{Tag: d, ID: e.PointerID})
}
}
case pointer.Release, pointer.Cancel:
d.pressed = false
if !d.dragging || e.PointerID != d.pid {
continue
}
d.dragging = false
}
return e, true
}
return pointer.Event{}, false
}
// Dragging reports whether it is currently in use.
func (d *Drag) Dragging() bool { return d.dragging }
// Pressed returns whether a pointer is pressing.
func (d *Drag) Pressed() bool { return d.pressed }
func (a Axis) String() string {
switch a {
case Horizontal:
return "Horizontal"
case Vertical:
return "Vertical"
default:
panic("invalid Axis")
}
}
func (ct ClickKind) String() string {
switch ct {
case KindPress:
return "KindPress"
case KindClick:
return "KindClick"
case KindCancel:
return "KindCancel"
default:
panic("invalid ClickKind")
}
}
func (s ScrollState) String() string {
switch s {
case StateIdle:
return "StateIdle"
case StateDragging:
return "StateDragging"
case StateFlinging:
return "StateFlinging"
default:
panic("unreachable")
}
}