zntg/ui/slider.go

package ui

import (
	"opslag.de/schobers/geom"
)

type Slider struct {
	ControlBase

	Orientation Orientation
	Minimum     float32
	Maximum     float32
	Value       float32

	handleWidth float32
	handle      sliderHandle
}

func BuildSlider(o Orientation, fn func(s *Slider)) *Slider {
	s := &Slider{Orientation: o}
	s.handle.OnDragStart(func(start geom.PointF32) { s.handleDrag(start) })
	s.handle.OnDragMove(func(_, pos geom.PointF32) { s.handleDrag(pos) })
	if fn != nil {
		fn(s)
	}
	return s
}

func (s *Slider) handleDrag(pos geom.PointF32) {
	start, length, _ := s.offsets()
	var offset float32
	if s.Orientation == OrientationHorizontal {
		offset = pos.X
	} else {
		offset = pos.Y
	}
	s.Value = s.Minimum + ((offset-start)/length)*(s.Maximum-s.Minimum)
	if s.Minimum < s.Maximum {
		s.Value = geom.Min32(s.Maximum, geom.Max32(s.Minimum, s.Value))
	} else {
		s.Value = geom.Min32(s.Minimum, geom.Max32(s.Maximum, s.Value))
	}
}

func (s *Slider) offsets() (start, length, center float32) {
	bounds := s.Bounds()
	if s.Orientation == OrientationHorizontal {
		start = bounds.Min.X
		length = bounds.Dx()
		center = .5 * (bounds.Min.Y + bounds.Max.Y)
	} else {
		start = bounds.Max.Y
		length = -bounds.Dy()
		center = .5 * (bounds.Min.X + bounds.Max.X)
	}
	if geom.Abs32(length) < s.handleWidth {
		start += .5 * length
		length = 0
	} else {
		if length < 0 {
			start -= .5 * s.handleWidth
			length += s.handleWidth
		} else {
			start += .5 * s.handleWidth
			length -= s.handleWidth
		}
	}
	return
}

func (s *Slider) Arrange(ctx Context, bounds geom.RectangleF32, offset geom.PointF32, parent Control) {
	s.ControlBase.Arrange(ctx, bounds, offset, parent)

	s.handleWidth = ctx.Style().Dimensions.ScrollbarWidth
	start, length, center := s.offsets()
	w := s.handleWidth
	w05 := .5 * w
	handleOffset := (s.Value - s.Minimum) / (s.Maximum - s.Minimum)
	if !geom.IsNaN32(handleOffset) {
		start += handleOffset * length
	}
	if s.Orientation == OrientationHorizontal {
		s.handle.Arrange(ctx, geom.RectF32(start-w05, center-w05, start+w05, center+w05), offset, s)
	} else {
		s.handle.Arrange(ctx, geom.RectF32(center-w05, start-w05, center+w05, start+w05), offset, s)
	}
}

func (s *Slider) DesiredSize(ctx Context) geom.PointF32 {
	w := ctx.Style().Dimensions.ScrollbarWidth
	if s.Orientation == OrientationHorizontal {
		return geom.PtF32(geom.NaN32(), w)
	}
	return geom.PtF32(w, geom.NaN32())
}

func (s *Slider) Handle(ctx Context, e Event) {
	s.handle.Handle(ctx, e)
	s.ControlBase.Handle(ctx, e)
}

func (s *Slider) Render(ctx Context) {
	s.RenderBackground(ctx)
	prim := ctx.Style().Palette.Primary
	start, length, center := s.offsets()
	if s.Orientation == OrientationHorizontal {
		ctx.Renderer().FillRectangle(geom.RectF32(start, center-1, start+length, center+1), prim)
	} else {
		ctx.Renderer().FillRectangle(geom.RectF32(center-1, start, center+1, start+length), prim)
	}
	s.handle.Render(ctx)
}

type sliderHandle struct {
	ControlBase

	handle Image
}

func (h *sliderHandle) im(ctx Context) Image {
	if h.handle != nil {
		return h.handle
	}
	size := h.Bounds().Size()
	center := geom.PtF32(.5*size.X-.5, .5*size.Y-.5)
	radius := 0.5 * geom.Min32(size.X, size.Y)
	h.handle = CreateImageAlpha(ctx, geom.Pt(int(size.X), int(size.Y)), func(p geom.PointF32) uint8 {
		dist := center.Distance(p)
		if dist < radius {
			if dist < (radius - 1) {
				return 255
			}
			return uint8(255 * (radius - dist))
		}
		return 0
	})
	return h.handle
}

func (h *sliderHandle) Handle(ctx Context, e Event) {
	h.ControlBase.Handle(ctx, e)
	if h.IsOver() {
		ctx.Renderer().SetMouseCursor(MouseCursorPointer)
	}
}

func (h *sliderHandle) Render(ctx Context) {
	color := ctx.Style().Palette.Primary
	if h.IsOver() {
		color = ctx.Style().Palette.PrimaryLight
	}
	ctx.Renderer().DrawImageOptions(h.im(ctx), h.Bounds().Min, DrawOptions{Tint: color})
}