mirror of
https://git.sr.ht/~eliasnaur/gio
synced 2026-07-08 02:45:38 +00:00
Elias Naur
@@ -0,0 +1,317 @@
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// SPDX-License-Identifier: Unlicense OR MIT
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package gesture
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import (
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"image"
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"math"
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"runtime"
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"time"
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"gioui.org/ui/f32"
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"gioui.org/ui/pointer"
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"gioui.org/ui"
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)
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type ClickEvent struct {
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Type ClickType
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Position f32.Point
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}
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type ClickState uint8
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type ClickType uint8
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type Click struct {
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State ClickState
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}
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type Scroll struct {
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dragging bool
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axis Axis
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estimator estimator
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flinger flinger
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pid pointer.ID
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grab bool
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last int
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// Leftover scroll.
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scroll float32
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}
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type flinger struct {
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// Current offset in pixels.
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x float32
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// Initial time.
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t0 time.Time
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// Initial velocity in pixels pr second.
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v0 float32
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}
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type Axis uint8
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const (
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Horizontal Axis = iota
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Vertical
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)
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const (
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StateNormal ClickState = iota
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StateFocused
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StatePressed
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)
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const (
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TypePress ClickType = iota
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TypeClick
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)
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var (
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touchSlop = ui.Dp(3)
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// Pixels/second.
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minFlingVelocity = ui.Dp(50)
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maxFlingVelocity = ui.Dp(8000)
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)
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const (
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thresholdVelocity = 1
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)
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func (c *Click) Op(a pointer.Area) pointer.OpHandler {
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return pointer.OpHandler{Area: a, Key: c}
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}
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func (c *Click) Update(q pointer.Events) []ClickEvent {
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var events []ClickEvent
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for _, e := range q.For(c) {
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switch e.Type {
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case pointer.Release:
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if c.State == StatePressed {
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events = append(events, ClickEvent{Type: TypeClick, Position: e.Position})
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}
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c.State = StateNormal
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case pointer.Cancel:
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c.State = StateNormal
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case pointer.Press:
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if c.State == StatePressed || !e.Hit {
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break
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}
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c.State = StatePressed
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events = append(events, ClickEvent{Type: TypePress, Position: e.Position})
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case pointer.Move:
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if c.State == StatePressed && !e.Hit {
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c.State = StateNormal
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} else if c.State < StateFocused {
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c.State = StateFocused
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}
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}
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}
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return events
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}
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func (s *Scroll) Op(a pointer.Area) ui.Op {
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oph := pointer.OpHandler{Area: a, Key: s, Grab: s.grab}
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if !s.flinger.Active() {
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return oph
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}
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return ui.Ops{oph, ui.OpRedraw{}}
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}
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func (s *Scroll) Stop() {
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s.flinger = flinger{}
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}
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func (s *Scroll) Dragging() bool {
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return s.dragging
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}
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func (s *Scroll) Scroll(cfg *ui.Config, q pointer.Events, axis Axis) int {
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if s.axis != axis {
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s.axis = axis
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return 0
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}
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total := 0
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for _, e := range q.For(s) {
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switch e.Type {
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case pointer.Press:
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if s.dragging || e.Source != pointer.Touch {
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break
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}
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s.Stop()
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s.estimator = estimator{}
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v := s.val(e.Position)
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s.last = int(math.Round(float64(v)))
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s.estimator.Sample(e.Time, v)
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s.dragging = true
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s.pid = e.PointerID
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case pointer.Release:
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if s.pid != e.PointerID {
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break
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}
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fling := s.estimator.Estimate()
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if slop, d := cfg.Pixels(touchSlop), fling.Distance; d >= slop || -slop >= d {
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if min, v := cfg.Pixels(minFlingVelocity), fling.Velocity; v >= min || -min >= v {
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max := cfg.Pixels(maxFlingVelocity)
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if v > max {
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v = max
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} else if v < -max {
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v = -max
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}
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s.flinger.Init(cfg.Now, v)
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}
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}
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fallthrough
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case pointer.Cancel:
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s.dragging = false
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s.grab = false
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case pointer.Move:
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// Scroll
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switch s.axis {
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case Horizontal:
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s.scroll += e.Scroll.X
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case Vertical:
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s.scroll += e.Scroll.Y
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}
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iscroll := int(math.Round(float64(s.scroll)))
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s.scroll -= float32(iscroll)
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total += iscroll
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if !s.dragging || s.pid != e.PointerID {
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continue
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}
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// Drag
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val := s.val(e.Position)
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s.estimator.Sample(e.Time, val)
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v := int(math.Round(float64(val)))
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dist := s.last - v
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if e.Priority < pointer.Grabbed {
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slop := cfg.Pixels(touchSlop)
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if dist := float32(dist); dist >= slop || -slop >= dist {
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s.grab = true
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}
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} else {
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s.last = v
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total += dist
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}
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}
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}
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total += s.flinger.Tick(cfg.Now)
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return total
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}
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func (s *Scroll) val(p f32.Point) float32 {
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if s.axis == Horizontal {
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return p.X
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} else {
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return p.Y
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}
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}
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func (f *flinger) Init(now time.Time, v0 float32) {
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f.t0 = now
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f.v0 = v0
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f.x = 0
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}
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func (f *flinger) Active() bool {
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return f.v0 != 0
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}
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// Tick computes and returns a fling distance since
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// the last time Tick was called.
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func (f *flinger) Tick(now time.Time) int {
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if !f.Active() {
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return 0
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}
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var k float32
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if runtime.GOOS == "darwin" {
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k = -2 // iOS
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} else {
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k = -4.2 // Android and default
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}
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t := now.Sub(f.t0)
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// The acceleration x''(t) of a point mass with a drag
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// force, f, proportional with velocity, x'(t), is
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// governed by the equation
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//
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// x''(t) = kx'(t)
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//
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// Given the starting position x(0) = 0, the starting
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// velocity x'(0) = v0, the position is then
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// given by
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//
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// x(t) = v0*e^(k*t)/k - v0/k
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//
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ekt := float32(math.Exp(float64(k) * t.Seconds()))
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x := f.v0*ekt/k - f.v0/k
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dist := x - f.x
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idist := int(math.Round(float64(dist)))
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f.x += float32(idist)
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// Solving for the velocity x'(t) gives us
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//
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// x'(t) = v0*e^(k*t)
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v := f.v0 * ekt
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if v < thresholdVelocity && v > -thresholdVelocity {
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f.v0 = 0
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}
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return idist
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}
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func Rect(sz image.Point) pointer.Area {
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return func(pos f32.Point) pointer.HitResult {
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if 0 <= pos.X && pos.X < float32(sz.X) &&
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0 <= pos.Y && pos.Y < float32(sz.Y) {
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return pointer.HitOpaque
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} else {
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return pointer.HitNone
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}
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}
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}
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func Ellipse(sz image.Point) pointer.Area {
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return func(pos f32.Point) pointer.HitResult {
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rx := float32(sz.X) / 2
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ry := float32(sz.Y) / 2
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rx2 := rx * rx
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ry2 := ry * ry
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xh := pos.X - rx
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yk := pos.Y - ry
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if xh*xh*ry2+yk*yk*rx2 <= rx2*ry2 {
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return pointer.HitOpaque
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} else {
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return pointer.HitNone
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}
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}
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}
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func (a Axis) String() string {
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switch a {
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case Horizontal:
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return "Horizontal"
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case Vertical:
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return "Vertical"
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default:
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panic("invalid Axis")
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}
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}
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func (ct ClickType) String() string {
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switch ct {
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case TypePress:
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return "TypePress"
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case TypeClick:
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return "TypeClick"
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default:
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panic("invalid ClickType")
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}
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}
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func (cs ClickState) String() string {
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switch cs {
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case StateNormal:
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return "StateNormal"
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case StateFocused:
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return "StateFocused"
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case StatePressed:
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return "StatePressed"
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default:
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panic("invalid ClickState")
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}
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}
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Reference in New Issue
Block a user