Blind pass at adding high performance scrolling into the renderer

screen.go

@@ -0,0 +1,40 @@
+package tea
+
+import (
+	"fmt"
+	"io"
+
+	te "github.com/muesli/termenv"
+)
+
+func clearLine(w io.Writer) {
+	fmt.Fprintf(w, te.CSI+te.EraseLineSeq, 2)
+}
+
+func cursorUp(w io.Writer) {
+	fmt.Fprintf(w, te.CSI+te.CursorUpSeq, 1)
+}
+
+func cursorDown(w io.Writer) {
+	fmt.Fprintf(w, te.CSI+te.CursorDownSeq, 1)
+}
+
+func insertLine(w io.Writer, numLines int) {
+	fmt.Fprintf(w, te.CSI+"%dL", numLines)
+}
+
+func moveCursor(w io.Writer, row, col int) {
+	fmt.Fprintf(w, te.CSI+te.CursorPositionSeq, row, col)
+}
+
+func saveCursorPosition(w io.Writer) {
+	fmt.Fprint(w, te.CSI+"s")
+}
+
+func restoreCursorPosition(w io.Writer) {
+	fmt.Fprint(w, te.CSI+"u")
+}
+
+func changeScrollingRegion(w io.Writer, top, bottom int) {
+	fmt.Fprintf(w, te.CSI+"%d;%dr", top, bottom)
+}