Add ClearScreen operation on Ctrl+L (#56)

* Add ClearScreen operation on Ctrl+L

* Remove TODO from clear screen in readme

* Don't use external command for ClearScreen

* Remove duplicate ClearScreen function

README.md

@@ -158,7 +158,7 @@ Notice: `Meta`+`B` is equals with `Alt`+`B` in windows.
 | `Ctrl`+`I` / `Tab` | Command line completion                  |
 | `Ctrl`+`J`         | Line feed                                |
 | `Ctrl`+`K`         | Cut text to the end of line              |
-| `Ctrl`+`L`         | Clean screen (TODO)                      |
+| `Ctrl`+`L`         | Clear screen                             |
 | `Ctrl`+`M`         | Same as Enter key                        |
 | `Ctrl`+`N` / `↓`   | Next line (in history)                   |
 | `Ctrl`+`P` / `↑`   | Prev line (in history)                   |

char.go

@@ -12,6 +12,7 @@ const (
 	CharTab       = 9
 	CharCtrlJ     = 10
 	CharKill      = 11
+	CharCtrlL     = 12
 	CharEnter     = 13
 	CharNext      = 14
 	CharPrev      = 16

operation.go

@@ -190,6 +190,9 @@ func (o *Operation) ioloop() {
 			o.buf.Clean()
 			o.t.SleepToResume()
 			o.Refresh()
+		case CharCtrlL:
+			ClearScreen(o.w)
+			o.Refresh()
 		case MetaBackspace, CharCtrlW:
 			o.buf.BackEscapeWord()
 		case CharEnter, CharCtrlJ:

utils_unix.go

@@ -3,6 +3,7 @@
 package readline
 
 import (
+	"io"
 	"os"
 	"os/signal"
 	"sync"
@@ -46,6 +47,11 @@ func GetScreenWidth() int {
 	return getWidth(syscall.Stdout)
 }
 
+// ClearScreen clears the console screen
+func ClearScreen(w io.Writer) (int, error) {
+	return w.Write([]byte("\033[H"))
+}
+
 func DefaultIsTerminal() bool {
 	return IsTerminal(syscall.Stdin) && IsTerminal(syscall.Stdout)
 }

utils_windows.go

@@ -2,7 +2,10 @@
 
 package readline
 
-import "syscall"
+import (
+	"io"
+	"syscall"
+)
 
 func SuspendMe() {
 }
@@ -24,6 +27,11 @@ func GetScreenWidth() int {
 	return int(info.dwSize.x)
 }
 
+// ClearScreen clears the console screen
+func ClearScreen(_ io.Writer) error {
+	return SetConsoleCursorPosition(&_COORD{0, 0})
+}
+
 func DefaultIsTerminal() bool {
 	return true
 }