ui: remove ui.Ops parameters from layouts and path builder structs

Layouts and path builders are transient and need an ops list for
operation. However, instead of passing the ops list to every method,
pass the list in an init method and store it for subsequent methods.

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

ui/measure/measure.go

@@ -233,6 +233,7 @@ func textPath(ppem fixed.Int26_6, f *opentype, str text.String) ui.OpBlock {
 	var lastPos f32.Point
 	var builder draw.PathBuilder
 	ops := new(ui.Ops)
+	builder.Init(ops)
 	var x fixed.Int26_6
 	var advIdx int
 	ops.Begin()
@@ -246,7 +247,7 @@ func textPath(ppem fixed.Int26_6, f *opentype, str text.String) ui.OpBlock {
 			pos := f32.Point{
 				X: float32(x) / 64,
 			}
-			builder.Move(ops, pos.Sub(lastPos))
+			builder.Move(pos.Sub(lastPos))
 			lastPos = pos
 			var lastArg f32.Point
 			// Convert sfnt.Segments to relative segments.
@@ -271,13 +272,13 @@ func textPath(ppem fixed.Int26_6, f *opentype, str text.String) ui.OpBlock {
 				}
 				switch fseg.Op {
 				case sfnt.SegmentOpMoveTo:
-					builder.Move(ops, args[0])
+					builder.Move(args[0])
 				case sfnt.SegmentOpLineTo:
-					builder.Line(ops, args[0])
+					builder.Line(args[0])
 				case sfnt.SegmentOpQuadTo:
-					builder.Quad(ops, args[0], args[1])
+					builder.Quad(args[0], args[1])
 				case sfnt.SegmentOpCubeTo:
-					builder.Cube(ops, args[0], args[1], args[2])
+					builder.Cube(args[0], args[1], args[2])
 				default:
 					panic("unsupported segment op")
 				}
@@ -287,6 +288,6 @@ func textPath(ppem fixed.Int26_6, f *opentype, str text.String) ui.OpBlock {
 		x += str.Advances[advIdx]
 		advIdx++
 	}
-	builder.End(ops)
+	builder.End()
 	return ops.End()
 }