objects/slider.go

package objects

import "image"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/tomo/theme"
import "git.tebibyte.media/tomo/tomo/input"
import "git.tebibyte.media/tomo/tomo/event"

// Slider is a control that selects a numeric value between 0 and 1.
type Slider struct {
	tomo.ContainerBox
	handle     *SliderHandle
	layout     sliderLayout
	dragging   bool
	dragOffset image.Point

	on struct {
		slide event.FuncBroadcaster
	}
}

// SliderHandle is a simple object that serves as a handle for sliders and
// scrollbars. It is completely inert.
type SliderHandle struct {
	tomo.Box
}

func newSlider (orient string, value float64) *Slider {
	this := &Slider {
		ContainerBox: tomo.NewContainerBox(),
		handle: &SliderHandle {
			Box: tomo.NewBox(),
		},
		layout: sliderLayout {
			vertical: orient == "vertical",
		},
	}

	this.Add(this.handle)
	this.SetFocusable(true)

	this.CaptureDND(true)
	this.CaptureMouse(true)
	this.CaptureScroll(true)
	this.CaptureKeyboard(true)

	this.SetValue(value)
	this.OnKeyDown(this.handleKeyDown)
	this.OnMouseDown(this.handleMouseDown)
	this.OnMouseUp(this.handleMouseUp)
	this.OnMouseMove(this.handleMouseMove)
	theme.Apply(this.handle, theme.R("objects", "SliderHandle", orient))
	theme.Apply(this,        theme.R("objects", "Slider", orient))
	return this
}

// NewVerticalSlider creates a new vertical slider with the specified value.
func NewVerticalSlider (value float64) *Slider {
	return newSlider("vertical", value)
}

// NewHorizontalSlider creates a new horizontal slider with the specified value.
func NewHorizontalSlider (value float64) *Slider {
	return newSlider("horizontal", value)
}

// SetValue sets the value of the slider between 0 and 1.
func (this *Slider) SetValue (value float64) {
	if value < 0 { value = 0 }
	if value > 1 { value = 1 }
	if value == this.layout.value { return }
	this.layout.value = value
	this.SetLayout(this.layout)
}

// Value returns the value of the slider between 0 and 1.
func (this *Slider) Value () float64 {
	return this.layout.value
}

// OnValueChange specifies a function to be called when the user moves the
// slider.
func (this *Slider) OnSlide (callback func ()) event.Cookie {
	return this.on.slide.Connect(callback)
}

func (this *Slider) handleKeyDown (key input.Key, numpad bool) {
	var increment float64; if this.layout.vertical {
		increment = -0.05
	} else {
		increment = 0.05
	}

	switch key {
	case input.KeyUp, input.KeyLeft:
		if this.Modifiers().Alt {
			this.SetValue(0)
		} else {
			this.SetValue(this.Value() - increment)
		}
	case input.KeyDown, input.KeyRight:
		if this.Modifiers().Alt {
			this.SetValue(1)
		} else {
			this.SetValue(this.Value() + increment)
		}
	case input.KeyHome:
		this.SetValue(0)
	case input.KeyEnd:
		this.SetValue(1)
	}
}

func (this *Slider) handleMouseDown (button input.Button) {
	pointer := this.MousePosition()
	handle  := this.handle.Bounds()
	
	within := pointer.In(handle)
	var above bool; if this.layout.vertical {
		above = pointer.Y < handle.Min.Y + handle.Dy() / 2
	} else {
		above = pointer.X < handle.Min.X + handle.Dx() / 2
	}

	switch button {
	case input.ButtonLeft:
		if within {
			this.dragging   = true
			this.dragOffset =
				pointer.Sub(this.handle.Bounds().Min).
				Add(this.InnerBounds().Min)
			this.drag()
		} else {
			this.dragOffset = this.fallbackDragOffset()
			this.dragging   = true
			this.drag()
		}
	case input.ButtonMiddle:
		if above {
			this.SetValue(0)
			this.on.slide.Broadcast()
		} else {
			this.SetValue(1)
			this.on.slide.Broadcast()
		}
	case input.ButtonRight:
		if above {
			this.SetValue(this.Value() - 0.05)
			this.on.slide.Broadcast()
		} else {
			this.SetValue(this.Value() + 0.05)
			this.on.slide.Broadcast()
		}
	}
}

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

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

func (this *Slider) drag () {
	pointer := this.MousePosition().Sub(this.dragOffset)
	gutter  := this.InnerBounds()
	handle  := this.handle.Bounds()

	if this.layout.vertical {
		this.SetValue (
			1 -
			float64(pointer.Y) /
			float64(gutter.Dy() - handle.Dy()))
	} else {
		this.SetValue (
			float64(pointer.X) /
			float64(gutter.Dx() - handle.Dx()))
	}
	this.on.slide.Broadcast()
}

func (this *Slider) fallbackDragOffset () image.Point {
	if this.layout.vertical {
		return this.InnerBounds().Min.
			Add(image.Pt(0, this.handle.Bounds().Dy() / 2))
	} else {
		return this.InnerBounds().Min.
			Add(image.Pt(this.handle.Bounds().Dx() / 2, 0))
	}
}

type sliderLayout struct {
	vertical bool
	value    float64
}

func (sliderLayout) MinimumSize (hints tomo.LayoutHints, boxes []tomo.Box) image.Point {
	if len(boxes) != 1 { return image.Pt(0, 0) }
	return boxes[0].MinimumSize()
}

func (this sliderLayout) Arrange (hints tomo.LayoutHints, boxes []tomo.Box) {
	if len(boxes) != 1 { return }
	handle := image.Rectangle { Max: boxes[0].MinimumSize() }
	gutter := hints.Bounds

	if this.vertical {
		height := gutter.Dy() - handle.Dy()
		offset := int(float64(height) * (1 - this.value))
		handle.Max.X = gutter.Dx()
		boxes[0].SetBounds (
			handle.
			Add(image.Pt(0, offset)).
			Add(gutter.Min))
	} else {
		width  := gutter.Dx() - handle.Dx()
		offset := int(float64(width) * this.value)
		handle.Max.Y = gutter.Dy()
		boxes[0].SetBounds (
			handle.
			Add(image.Pt(offset, 0)).
			Add(gutter.Min))
	}
}