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color_wheel.go
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color_wheel.go
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package dialog
import (
"image"
"image/color"
"image/draw"
"math"
"math/cmplx"
"fyne.io/fyne/v2"
"fyne.io/fyne/v2/canvas"
"fyne.io/fyne/v2/driver/desktop"
internalwidget "fyne.io/fyne/v2/internal/widget"
"fyne.io/fyne/v2/theme"
"fyne.io/fyne/v2/widget"
)
var _ fyne.Widget = (*colorWheel)(nil)
var _ fyne.Tappable = (*colorWheel)(nil)
var _ fyne.Draggable = (*colorWheel)(nil)
// colorWheel displays a circular color gradient and triggers the callback when tapped.
type colorWheel struct {
widget.BaseWidget
generator func(w, h int) image.Image
cache draw.Image
onChange func(int, int, int, int)
Hue int // Range 0-360 (degrees)
Saturation, Lightness int // Range 0-100 (percent)
Alpha int // Range 0-255
}
// newColorWheel returns a new color area that triggers the given onChange callback when tapped.
func newColorWheel(onChange func(int, int, int, int)) *colorWheel {
a := &colorWheel{
onChange: onChange,
}
a.generator = func(w, h int) image.Image {
if a.cache == nil || a.cache.Bounds().Dx() != w || a.cache.Bounds().Dy() != h {
rect := image.Rect(0, 0, w, h)
a.cache = image.NewRGBA(rect)
}
for x := 0; x < w; x++ {
for y := 0; y < h; y++ {
if c := a.colorAt(x, y, w, h); c != nil {
a.cache.Set(x, y, c)
}
}
}
return a.cache
}
a.ExtendBaseWidget(a)
return a
}
// Cursor returns the cursor type of this widget.
func (a *colorWheel) Cursor() desktop.Cursor {
return desktop.CrosshairCursor
}
// CreateRenderer is a private method to Fyne which links this widget to its renderer.
func (a *colorWheel) CreateRenderer() fyne.WidgetRenderer {
raster := &canvas.Raster{
Generator: a.generator,
}
background := newCheckeredBackground(true)
x := canvas.NewLine(color.Black)
y := canvas.NewLine(color.Black)
return &colorWheelRenderer{
BaseRenderer: internalwidget.NewBaseRenderer([]fyne.CanvasObject{background, raster, x, y}),
area: a,
background: background,
raster: raster,
x: x,
y: y,
}
}
// MinSize returns the size that this widget should not shrink below.
func (a *colorWheel) MinSize() fyne.Size {
a.ExtendBaseWidget(a)
return a.BaseWidget.MinSize()
}
// SetHSLA updates the selected color in the wheel.
func (a *colorWheel) SetHSLA(hue, saturation, lightness, alpha int) {
if a.Hue == hue && a.Saturation == saturation && a.Lightness == lightness && a.Alpha == alpha {
return
}
a.Hue = hue
a.Saturation = saturation
a.Lightness = lightness
a.Alpha = alpha
a.Refresh()
}
// Tapped is called when a pointer tapped event is captured and triggers any change handler.
func (a *colorWheel) Tapped(event *fyne.PointEvent) {
a.trigger(event.Position)
}
// Dragged is called when a pointer drag event is captured and triggers any change handler
func (a *colorWheel) Dragged(event *fyne.DragEvent) {
a.trigger(event.Position)
}
// DragEnd is called when a pointer drag ends
func (a *colorWheel) DragEnd() {
}
func (a *colorWheel) colorAt(x, y, w, h int) color.Color {
width, height := float64(w), float64(h)
dx := float64(x) - (width / 2.0)
dy := float64(y) - (height / 2.0)
radius, radians := cmplx.Polar(complex(dx, dy))
limit := math.Min(width, height) / 2.0
if radius > limit {
// Out of bounds
return color.Transparent
}
degrees := radians * (180.0 / math.Pi)
hue := wrapHue(int(degrees))
saturation := int(radius / limit * 100.0)
red, green, blue := hslToRgb(hue, saturation, a.Lightness)
return &color.NRGBA{
R: uint8(red),
G: uint8(green),
B: uint8(blue),
A: uint8(a.Alpha),
}
}
func (a *colorWheel) locationForPosition(pos fyne.Position) (x, y int) {
can := fyne.CurrentApp().Driver().CanvasForObject(a)
x, y = int(pos.X), int(pos.Y)
if can != nil {
x, y = can.PixelCoordinateForPosition(pos)
}
return
}
func (a *colorWheel) selection(width, height float32) (float32, float32) {
w, h := float64(width), float64(height)
radius := float64(a.Saturation) / 100.0 * math.Min(w, h) / 2.0
degrees := float64(a.Hue)
radians := degrees * math.Pi / 180.0
c := cmplx.Rect(radius, radians)
return float32(real(c) + w/2.0), float32(imag(c) + h/2.0)
}
func (a *colorWheel) trigger(pos fyne.Position) {
x, y := a.locationForPosition(pos)
if c, f := a.cache, a.onChange; c != nil && f != nil {
b := c.Bounds()
width, height := float64(b.Dx()), float64(b.Dy())
dx := float64(x) - (width / 2)
dy := float64(y) - (height / 2)
radius, radians := cmplx.Polar(complex(dx, dy))
limit := math.Min(width, height) / 2.0
if radius > limit {
// Out of bounds
return
}
degrees := radians * (180.0 / math.Pi)
a.Hue = wrapHue(int(degrees))
a.Saturation = int(radius / limit * 100.0)
f(a.Hue, a.Saturation, a.Lightness, a.Alpha)
}
a.Refresh()
}
type colorWheelRenderer struct {
internalwidget.BaseRenderer
area *colorWheel
background *canvas.Raster
raster *canvas.Raster
x, y *canvas.Line
}
func (r *colorWheelRenderer) Layout(size fyne.Size) {
x, y := r.area.selection(size.Width, size.Height)
r.x.Position1 = fyne.NewPos(0, y)
r.x.Position2 = fyne.NewPos(size.Width, y)
r.y.Position1 = fyne.NewPos(x, 0)
r.y.Position2 = fyne.NewPos(x, size.Height)
r.raster.Move(fyne.NewPos(0, 0))
r.raster.Resize(size)
r.background.Resize(size)
}
func (r *colorWheelRenderer) MinSize() fyne.Size {
return r.raster.MinSize().Max(fyne.NewSize(128, 128))
}
func (r *colorWheelRenderer) Refresh() {
s := r.area.Size()
if s.IsZero() {
r.area.Resize(r.area.MinSize())
} else {
r.Layout(s)
}
r.x.StrokeColor = theme.Color(theme.ColorNameForeground)
r.x.Refresh()
r.y.StrokeColor = theme.Color(theme.ColorNameForeground)
r.y.Refresh()
r.raster.Refresh()
r.background.Refresh()
canvas.Refresh(r.area)
}