all: replace InvalidateOp with InvalidateCmd command

Curiously, InvalidateCmd is probably the only command that is appropriate
to call during layout.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/editor.go

@@ -692,8 +692,7 @@ func (e *Editor) layout(gtx layout.Context, textMaterial, selectMaterial op.Call
 		const timePerBlink = time.Second / blinksPerSecond
 		nextBlink := now.Add(timePerBlink/2 - dt%(timePerBlink/2))
 		if blinking {
-			redraw := op.InvalidateOp{At: nextBlink}
-			redraw.Add(gtx.Ops)
+			gtx.Execute(op.InvalidateCmd{At: nextBlink})
 		}
 		e.showCaret = e.focused && (!blinking || dt%timePerBlink < timePerBlink/2)
 	}

widget/material/button.go

@@ -258,7 +258,7 @@ func drawInk(gtx layout.Context, c widget.Press) {
 
 	// Animate only ended presses, and presses that are fading in.
 	if !c.End.IsZero() || sizet <= 1.0 {
-		op.InvalidateOp{}.Add(gtx.Ops)
+		gtx.Execute(op.InvalidateCmd{})
 	}
 
 	if sizet > 1.0 {

widget/material/loader.go

@@ -47,7 +47,7 @@ func (l LoaderStyle) Layout(gtx layout.Context) layout.Dimensions {
 	}.Add(gtx.Ops)
 	defer op.Offset(image.Pt(-radius, -radius)).Push(gtx.Ops).Pop()
 	paint.PaintOp{}.Add(gtx.Ops)
-	op.InvalidateOp{}.Add(gtx.Ops)
+	gtx.Execute(op.InvalidateCmd{})
 	return layout.Dimensions{
 		Size: sz,
 	}