1 files changed, 35 insertions, 0 deletions
diff --git a/intercepter.go b/intercepter.go
new file mode 100644
index 0000000..95df3c6
--- /dev/null
+++ b/intercepter.go
@@ -0,0 +1,35 @@
+package gui
+
+import (
+	"image"
+	"image/draw"
+)
+
+// Intercepter represents an element that can interact with Envs.
+// An Intercepter can modify Events, stop them or emit arbitrary ones.
+// It can also put itself in the draw pipeline, for throttling very
+// expensive draw calls for example.
+type Intercepter interface {
+	Intercept(Env) Env
+}
+
+// RedrawIntercepter is a basic Intercepter, it is meant for use in simple Layouts
+// that only need to redraw themselves.
+type RedrawIntercepter struct {
+	Redraw func(draw.Image, image.Rectangle)
+}
+
+func (ri RedrawIntercepter) Intercept(parent Env) Env {
+	return newEnv(parent,
+		func(e Event, c chan<- Event) {
+			c <- e
+			if resize, ok := e.(Resize); ok {
+				parent.Draw() <- func(drw draw.Image) image.Rectangle {
+					ri.Redraw(drw, resize.Rectangle)
+					return resize.Rectangle
+				}
+			}
+		},
+		send, // forward draw functions un-modified
+		func() {})
+}