objects/colorpicker.go

package objects

import "image/color"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/tomo/input"
import "git.tebibyte.media/tomo/tomo/event"
import "git.tebibyte.media/tomo/tomo/canvas"
import "git.tebibyte.media/tomo/objects/layouts"
import "git.tebibyte.media/tomo/objects/internal"

// ColorPicker allows the user to pick a color by controlling its HSBA
// parameters.
type ColorPicker struct {
	tomo.ContainerBox
	value internal.HSVA
	
	pickerMap   *colorPickerMap
	hueSlider   *Slider
	alphaSlider *Slider
	
	on struct {
		valueChange event.FuncBroadcaster
	}
}

// NewColorPicker creates a new color picker with the specified color.
func NewColorPicker (value color.Color) *ColorPicker {
	picker := &ColorPicker {
		ContainerBox: tomo.NewContainerBox(),
	}
	picker.SetRole(tomo.R("objects", "ColorPicker", ""))
	picker.SetLayout(layouts.Row { true, false, false })
	picker.pickerMap = newColorPickerMap(picker)
	picker.Add(picker.pickerMap)
	
	picker.hueSlider = NewVerticalSlider(0.0)
	picker.Add(picker.hueSlider)
	picker.hueSlider.OnValueChange(func () {
		picker.value.H = picker.hueSlider.Value()
		picker.on.valueChange.Broadcast()
		picker.pickerMap.Invalidate()
	})
	
	picker.alphaSlider = NewVerticalSlider(0.0)
	picker.Add(picker.alphaSlider)
	picker.alphaSlider.OnValueChange(func () {
		picker.value.A = uint8(picker.alphaSlider.Value() * 255)
		picker.on.valueChange.Broadcast()
		picker.pickerMap.Invalidate()
	})
	
	if value == nil { value = color.Transparent }
	picker.SetValue(value)
	return picker
}

// Value returns the color of the picker.
func (this *ColorPicker) Value () color.Color {
	return this.value
}

// SetValue sets the color of the picker.
func (this *ColorPicker) SetValue (value color.Color) {
	if value == nil { value = color.Transparent }
	this.value = internal.RGBAToHSVA(value.RGBA())
	this.hueSlider.SetValue(this.value.H)
	this.alphaSlider.SetValue(float64(this.value.A) / 255)
}

// OnValueChange specifies a function to be called when the user changes the
// swatch's color.
func (this *ColorPicker) OnValueChange (callback func ()) event.Cookie {
	return this.on.valueChange.Connect(callback)
}

// RGBA satisfies the color.Color interface
func (this *ColorPicker) RGBA () (r, g, b, a uint32) {
	return this.value.RGBA()
}

type colorPickerMap struct {
	tomo.CanvasBox
	dragging bool
	parent *ColorPicker
}

func newColorPickerMap (parent *ColorPicker) *colorPickerMap {
	picker := &colorPickerMap {
		CanvasBox: tomo.NewCanvasBox(),
		parent: parent,
	}
	picker.SetDrawer(picker)
	picker.SetRole(tomo.R("objects", "ColorPickerMap", ""))
	picker.OnMouseUp(picker.handleMouseUp)
	picker.OnMouseDown(picker.handleMouseDown)
	picker.OnMouseMove(picker.handleMouseMove)
	return picker
}

func (this *colorPickerMap) handleMouseDown (button input.Button) {
	if button != input.ButtonLeft { return }
	this.dragging = true
	this.drag()
}

func (this *colorPickerMap) handleMouseUp (button input.Button) {
	if button != input.ButtonLeft || !this.dragging { return }
	this.dragging = false
}

func (this *colorPickerMap) handleMouseMove () {
	if !this.dragging { return }
	this.drag()
}

func (this *colorPickerMap) drag () {
	pointer := this.MousePosition()
	bounds  := this.InnerBounds()
	this.parent.value.S =     float64(pointer.X - bounds.Min.X) / float64(bounds.Dx())
	this.parent.value.V = 1 - float64(pointer.Y - bounds.Min.Y) / float64(bounds.Dy())
	this.parent.value = this.parent.value.Canon()
	this.parent.on.valueChange.Broadcast()
	this.Invalidate()
}

func (this *colorPickerMap) Draw (can canvas.Canvas) {
	bounds := can.Bounds()
	for y := bounds.Min.Y; y < bounds.Max.Y; y ++ {
	for x := bounds.Min.X; x < bounds.Max.X; x ++ {
		xx := x - bounds.Min.X
		yy := y - bounds.Min.Y
		
		pixel := internal.HSVA {
			H: this.parent.value.H,
			S:     float64(xx) / float64(bounds.Dx()),
			V: 1 - float64(yy) / float64(bounds.Dy()),
			A: 255,
		}
		
		sPos := int(     this.parent.value.S  * float64(bounds.Dx()))
		vPos := int((1 - this.parent.value.V) * float64(bounds.Dy()))
		sDist := sPos - xx
		vDist := vPos - yy
		crosshair :=
			(sDist == 0 || vDist == 0) &&
			-8 < sDist && sDist < 8 &&
			-8 < vDist && vDist < 8
		if crosshair {
			pixel.S = 1 - pixel.S
			pixel.V = 1 - pixel.V
		}
		
		can.Set(x, y, pixel)
	}}
}