widget/material: add hover state to window decorations

Decorations buttons already use widget.Clickable and draw press ink, but they don't draw a hover/focus background. This makes custom window decorations appear unresponsive when the pointer is over minimize, maximize, or close buttons.

Register each button's system action over its clickable area and draw the same hovered background used by other material buttons. This also lets platforms query the button action from the material decorations hit area.

Signed-off-by: qiannian <qianniancn@gmail.com>

widget/material/decorations.go

@@ -5,7 +5,6 @@ import (
 	"image/color"
 
 	"gioui.org/f32"
-	"gioui.org/io/semantic"
 	"gioui.org/io/system"
 	"gioui.org/layout"
 	"gioui.org/op"
@@ -86,21 +85,10 @@ func (d DecorationsStyle) layoutDecorations(gtx layout.Context) layout.Dimension
 					continue
 				}
 				cl := d.Decorations.Clickable(a)
-				dims := cl.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
-					semantic.Button.Add(gtx.Ops)
-					return layout.Background{}.Layout(gtx,
-						func(gtx layout.Context) layout.Dimensions {
-							defer clip.Rect{Max: gtx.Constraints.Min}.Push(gtx.Ops).Pop()
-							for _, c := range cl.History() {
-								drawInk(gtx, c)
-							}
-							return layout.Dimensions{Size: gtx.Constraints.Min}
-						},
-						func(gtx layout.Context) layout.Dimensions {
+				dims := Clickable(gtx, cl, func(gtx layout.Context) layout.Dimensions {
+					system.ActionInputOp(a).Add(gtx.Ops)
 					paint.ColorOp{Color: d.Foreground}.Add(gtx.Ops)
 					return inset.Layout(gtx, w)
-						},
-					)
 				})
 				size.X += dims.Size.X
 				if size.Y < dims.Size.Y {