User interface toolkit for Go with support for SDL2 and HTML Canvas render targets.
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package ui
import (
"errors"
"fmt"
"sync"
"git.kirsle.net/go/render"
"git.kirsle.net/go/render/event"
)
// Event is a named event that the supervisor will send.
type Event int
// Events.
const (
NullEvent Event = iota
MouseOver
MouseOut
MouseDown
MouseUp
Click
KeyDown
KeyUp
KeyPress
Drop
Compute // fired whenever the widget runs Compute
Present // fired whenever the widget runs Present
)
// EventData carries common data to event handlers.
type EventData struct {
// Point is usually the cursor position on click and mouse events.
Point render.Point
// Engine is the render engine on Compute and Present events.
Engine render.Engine
}
// Supervisor keeps track of widgets of interest to notify them about
// interaction events such as mouse hovers and clicks in their general
// vicinity.
type Supervisor struct {
lock sync.RWMutex
serial int // ID number of each widget added in order
widgets map[int]WidgetSlot // map of widget ID to WidgetSlot
hovering map[int]interface{} // map of widgets under the cursor
clicked map[int]interface{} // map of widgets being clicked
dd *DragDrop
}
// WidgetSlot holds a widget with a unique ID number in a sorted list.
type WidgetSlot struct {
id int
widget Widget
}
// NewSupervisor creates a supervisor.
func NewSupervisor() *Supervisor {
return &Supervisor{
widgets: map[int]WidgetSlot{},
hovering: map[int]interface{}{},
clicked: map[int]interface{}{},
dd: NewDragDrop(),
}
}
// DragStart sets the drag state.
func (s *Supervisor) DragStart() {
s.dd.Start()
}
// DragStop stops the drag state.
func (s *Supervisor) DragStop() {
s.dd.Stop()
}
// IsDragging returns whether the drag state is enabled.
func (s *Supervisor) IsDragging() bool {
return s.dd.IsDragging()
}
// Error messages that may be returned by Supervisor.Loop()
var (
// The caller should STOP forwarding any mouse or keyboard events to any
// other handles for the remainder of this tick.
ErrStopPropagation = errors.New("stop all event propagation")
)
// Loop to check events and pass them to managed widgets.
//
// Useful errors returned by this may be:
// - ErrStopPropagation
func (s *Supervisor) Loop(ev *event.State) error {
var (
XY = render.Point{
X: ev.CursorX,
Y: ev.CursorY,
}
)
// See if we are hovering over any widgets.
hovering, outside := s.Hovering(XY)
// If we are dragging something around, do not trigger any mouse events
// to other widgets but DO notify any widget we dropped on top of!
if s.dd.IsDragging() {
if !ev.Button1 && !ev.Button3 {
// The mouse has been released. TODO: make mouse button important?
for _, child := range hovering {
child.widget.Event(Drop, EventData{
Point: XY,
})
}
s.DragStop()
}
return ErrStopPropagation
}
for _, child := range hovering {
var (
id = child.id
w = child.widget
)
if w.Hidden() {
// TODO: somehow the Supervisor wasn't triggering hidden widgets
// anyway, but I don't know why. Adding this check for safety.
continue
}
// Cursor has intersected the widget.
if _, ok := s.hovering[id]; !ok {
w.Event(MouseOver, EventData{
Point: XY,
})
s.hovering[id] = nil
}
_, isClicked := s.clicked[id]
if ev.Button1 {
if !isClicked {
w.Event(MouseDown, EventData{
Point: XY,
})
s.clicked[id] = nil
}
} else if isClicked {
w.Event(MouseUp, EventData{
Point: XY,
})
w.Event(Click, EventData{
Point: XY,
})
delete(s.clicked, id)
}
}
for _, child := range outside {
var (
id = child.id
w = child.widget
)
// Cursor is not intersecting the widget.
if _, ok := s.hovering[id]; ok {
w.Event(MouseOut, EventData{
Point: XY,
})
delete(s.hovering, id)
}
if _, ok := s.clicked[id]; ok {
w.Event(MouseUp, EventData{
Point: XY,
})
delete(s.clicked, id)
}
}
return nil
}
// Hovering returns all of the widgets managed by Supervisor that are under
// the mouse cursor. Returns the set of widgets below the cursor and the set
// of widgets not below the cursor.
func (s *Supervisor) Hovering(cursor render.Point) (hovering, outside []WidgetSlot) {
var XY = cursor // for shorthand
hovering = []WidgetSlot{}
outside = []WidgetSlot{}
// Check all the widgets under our care.
for child := range s.Widgets() {
var (
w = child.widget
P = AbsolutePosition(w)
S = w.Size()
P2 = render.Point{
X: P.X + S.W,
Y: P.Y + S.H,
}
)
if XY.X >= P.X && XY.X < P2.X && XY.Y >= P.Y && XY.Y < P2.Y {
// Cursor intersects the widget.
hovering = append(hovering, child)
} else {
outside = append(outside, child)
}
}
return hovering, outside
}
// Widgets returns a channel of widgets managed by the supervisor in the order
// they were added.
func (s *Supervisor) Widgets() <-chan WidgetSlot {
pipe := make(chan WidgetSlot)
go func() {
for i := 0; i < s.serial; i++ {
if w, ok := s.widgets[i]; ok {
pipe <- w
}
}
close(pipe)
}()
return pipe
}
// Present all widgets managed by the supervisor.
func (s *Supervisor) Present(e render.Engine) {
s.lock.RLock()
defer s.lock.RUnlock()
fmt.Println("!!! ui.Supervisor.Present() is deprecated")
// for child := range s.Widgets() {
// var w = child.widget
// w.Present(e, w.Point())
// }
}
// Add a widget to be supervised.
func (s *Supervisor) Add(w Widget) {
s.lock.Lock()
s.widgets[s.serial] = WidgetSlot{
id: s.serial,
widget: w,
}
s.serial++
s.lock.Unlock()
}