1 files changed, 34 insertions, 0 deletions
diff --git a/shiny/driver/internal/drawer/drawer.go b/shiny/driver/internal/drawer/drawer.go
new file mode 100644
index 0000000..230a174
--- /dev/null
+++ b/shiny/driver/internal/drawer/drawer.go
@@ -0,0 +1,34 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package drawer provides functions that help implement screen.Drawer methods.
+package drawer // import "golang.org/x/exp/shiny/driver/internal/drawer"
+
+import (
+	"image"
+	"image/draw"
+
+	"golang.org/x/exp/shiny/screen"
+	"golang.org/x/image/math/f64"
+)
+
+// Copy implements the Copy method of the screen.Drawer interface by calling
+// the Draw method of that same interface.
+func Copy(dst screen.Drawer, dp image.Point, src screen.Texture, sr image.Rectangle, op draw.Op, opts *screen.DrawOptions) {
+	dst.Draw(f64.Aff3{
+		1, 0, float64(dp.X - sr.Min.X),
+		0, 1, float64(dp.Y - sr.Min.Y),
+	}, src, sr, op, opts)
+}
+
+// Scale implements the Scale method of the screen.Drawer interface by calling
+// the Draw method of that same interface.
+func Scale(dst screen.Drawer, dr image.Rectangle, src screen.Texture, sr image.Rectangle, op draw.Op, opts *screen.DrawOptions) {
+	rx := float64(dr.Dx()) / float64(sr.Dx())
+	ry := float64(dr.Dy()) / float64(sr.Dy())
+	dst.Draw(f64.Aff3{
+		rx, 0, float64(dr.Min.X) - rx*float64(sr.Min.X),
+		0, ry, float64(dr.Min.Y) - ry*float64(sr.Min.Y),
+	}, src, sr, op, opts)
+}