2 files changed, 30 insertions(+), 16 deletions(-)

M widget/float.go
M widget/material/slider.go

@@ 13,8 13,9 @@ import (
 
 // Float is for selecting a value in a range.
 type Float struct {
-	Value float32
-	Axis  layout.Axis
+	Value  float32
+	Axis   layout.Axis
+	Invert bool
 
 	drag    gesture.Drag
 	pos     float32 // position normalized to [0, 1]


@@ 43,7 44,10 @@ func (f *Float) Layout(gtx layout.Context, pointerMargin int, min, max float32) 
 	if de != nil {
 		xy := de.Position.X
 		if f.Axis == layout.Vertical {
-			xy = de.Position.Y
+			xy = f.length - de.Position.Y
+		}
+		if f.Invert {
+			xy = f.length - xy
 		}
 		f.pos = xy / f.length
 		value = min + (max-min)*f.pos

@@ 61,26 61,36 @@ func (s SliderStyle) Layout(gtx layout.Context) layout.Dimensions {
 		color = f32color.Disabled(color)
 	}
 
-	// Draw track before thumb.
-	track := image.Rectangle{
-		Min: axis.Convert(image.Pt(thumbRadius, sizeCross/2-trackWidth/2)),
-		Max: axis.Convert(image.Pt(thumbPos, sizeCross/2+trackWidth/2)),
+	rect := func(minx, miny, maxx, maxy int) image.Rectangle {
+		r := image.Rect(minx, miny, maxx, maxy)
+		if s.Float.Invert != (axis == layout.Vertical) {
+			r.Max.X, r.Min.X = sizeMain-r.Min.X, sizeMain-r.Max.X
+		}
+		r.Min = axis.Convert(r.Min)
+		r.Max = axis.Convert(r.Max)
+		return r
 	}
+
+	// Draw track before thumb.
+	track := rect(
+		thumbRadius, sizeCross/2-trackWidth/2,
+		thumbPos, sizeCross/2+trackWidth/2,
+	)
 	paint.FillShape(gtx.Ops, color, clip.Rect(track).Op())
 
 	// Draw track after thumb.
-	track = image.Rectangle{
-		Min: axis.Convert(image.Pt(thumbPos, axis.Convert(track.Min).Y)),
-		Max: axis.Convert(image.Pt(sizeMain-thumbRadius, axis.Convert(track.Max).Y)),
-	}
+	track = rect(
+		thumbPos, axis.Convert(track.Min).Y,
+		sizeMain-thumbRadius, axis.Convert(track.Max).Y,
+	)
 	paint.FillShape(gtx.Ops, f32color.MulAlpha(color, 96), clip.Rect(track).Op())
 
 	// Draw thumb.
-	pt := axis.Convert(image.Pt(thumbPos, sizeCross/2))
-	thumb := image.Rectangle{
-		Min: image.Pt(pt.X-thumbRadius, pt.Y-thumbRadius),
-		Max: image.Pt(pt.X+thumbRadius, pt.Y+thumbRadius),
-	}
+	pt := image.Pt(thumbPos, sizeCross/2)
+	thumb := rect(
+		pt.X-thumbRadius, pt.Y-thumbRadius,
+		pt.X+thumbRadius, pt.Y+thumbRadius,
+	)
 	paint.FillShape(gtx.Ops, color, clip.Ellipse(thumb).Op(gtx.Ops))
 
 	return layout.Dimensions{Size: size}