Erase full screen

drivers/cga/backend.go

@@ -17,6 +17,14 @@ type Backend interface {
 	WriteByte(ch byte)
 }
 
+type EraseMethod uint8
+
+const (
+	EraseMethod_Unknown EraseMethod = iota
+	EraseMethod_Line
+	EraseMethod_All
+)
+
 const (
 	CRTPORT = 0x3d4
 	bs      = '\b'

drivers/cga/cga.go

@@ -21,15 +21,21 @@ func setCursorColumn(n int) {
 	getbackend().SetPos(pos)
 }
 
-func eraseLine(method int) {
+func eraseLine(method EraseMethod) {
 	backend := getbackend()
 	pos := backend.GetPos()
 	switch method {
-	case 0:
+	case EraseMethod_Line:
 		end := (pos/80 + 1) * 80
 		for i := pos; i < end; i++ {
 			backend.WritePos(i, ' ')
 		}
+
+	case EraseMethod_All:
+		for i := 0; i < 25*80; i++ {
+			backend.WritePos(i, ' ')
+		}
+
 	default:
 		panic("unsupported erase line method")
 	}
@@ -38,7 +44,7 @@ func eraseLine(method int) {
 func writeCSI(action byte, params []string) {
 	// fmt.Fprintf(os.Stderr, "action:%c, params:%v\n", action, params)
 	switch action {
-	// set cursor
+	// set cursor column
 	case 'G':
 		if len(params) == 0 {
 			setCursorColumn(1)
@@ -49,11 +55,21 @@ func writeCSI(action byte, params []string) {
 	// erase line
 	case 'K':
 		if len(params) == 0 {
-			eraseLine(0)
+			eraseLine(EraseMethod_Line)
 		} else {
-			n, _ := strconv.Atoi(params[0])
-			eraseLine(n)
+			//n, _ := strconv.Atoi(params[0])
+			eraseLine(EraseMethod_Unknown)
 		}
+
+	// Erase screen - note; this action *looks* like it ought
+	// to be just <ESC>[J - which is 'erase from current line to
+	// bottom of screen', but I actually want it to mimic <ESC>[2J
+	// which is 'erase screen and return to top'
+	//
+	// Hopefully nobody ever uses my fork if they expect that functionality
+	case 'J':
+		eraseLine(EraseMethod_All)
+
 	default:
 		panic("unsupported CSI action")
 	}