add layout from Keitio

1 files changed, 43 insertions, 0 deletions

diff --git a/gui/layout/intercepter.go b/gui/layout/intercepter.go
new file mode 100644
index 0000000..d25d578
--- /dev/null
+++ b/gui/layout/intercepter.go
@@ -0,0 +1,43 @@
+package layout
+
+import (
+	"image"
+	"image/draw"
+
+	"volute/gui"
+)
+
+// 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(gui.Env) gui.Env
+}
+
+var _ Intercepter = RedrawIntercepter{}
+
+// 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)
+}
+
+// Intercept implements Intercepter
+func (ri RedrawIntercepter) Intercept(env gui.Env) gui.Env {
+	out, in := gui.MakeEventsChan()
+	go func() {
+		for e := range env.Events() {
+			in <- e
+			if resize, ok := e.(gui.Resize); ok {
+				env.Draw() <- func(drw draw.Image) image.Rectangle {
+					bounds := resize.Rectangle
+					ri.Redraw(drw, bounds)
+					return bounds
+				}
+			}
+		}
+	}()
+	ret := &muxEnv{out, env.Draw()}
+	return ret
+}