gui: a /dev/draw layer in go, with no cgo and no devdraw

9fans.net/go/draw builds for plan9 but shells out to plan9port's
devdraw, which 9front does not have. This talks to /dev/draw itself:
the protocol is file i/o, so a pure-go client is a few hundred lines
under an already-complete idea.

draw/keyboard.go opens /dev/cons and turns the console raw, as
libdraw's initkeyboard does. Without it rio keeps its line editor on
the window and paints what you type over the drawing.

draw/snarf.go writes /dev/snarf, which is what every other program on
the system means by copy.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/gui/draw/snarf.go b/gui/draw/snarf.go
new file mode 100644
index 0000000..ae26edd
--- /dev/null
+++ b/gui/draw/snarf.go
@@ -0,0 +1,15 @@
+package draw
+
+import "os"
+
+// Snarf puts text on the system snarf buffer, which is what every other
+// program on the system means by "copy".
+func Snarf(dev, text string) error {
+	f, err := os.OpenFile(dev+"/snarf", os.O_WRONLY|os.O_TRUNC, 0)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = f.WriteString(text)
+	return err
+}