Ctrl-L clears the KDL screen.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25233 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/kernel/debug/blue_screen.cpp

@@ -595,6 +595,14 @@ blue_screen_enter(bool debugOutput)
 }
 
 
+void
+blue_screen_clear_screen(void)
+{
+	sModule->clear(sScreen.attr);
+	move_cursor(0, 0);
+}
+
+
 char
 blue_screen_getchar(void)
 {

src/system/kernel/debug/blue_screen.h

@@ -16,6 +16,7 @@ extern "C" {
 status_t blue_screen_init(void);
 status_t blue_screen_enter(bool debugOutput);
 
+void blue_screen_clear_screen(void);
 char blue_screen_getchar(void);
 void blue_screen_putchar(char c);
 void blue_screen_puts(const char *text);

src/system/kernel/debug/debug.cpp

@@ -376,6 +376,28 @@ read_line(char *buffer, int32 maxLength,
 					length = position;
 				}
 				break;
+			case 0x1f & 'L':	// CTRL-L -- clear screen
+				if (sBlueScreenOutput) {
+					// All the following needs to be transparent for the
+					// serial debug output. I.e. after clearing the screen
+					// we have to get the on-screen line into the visual state
+					// it should have.
+
+					// clear screen
+					blue_screen_clear_screen();
+
+					// reprint line
+					buffer[length] = '\0';
+					blue_screen_puts(kKDLPrompt);
+					blue_screen_puts(buffer);
+
+					// reposition cursor
+					if (position < length) {
+						for (int i = length; i > position; i--)
+							blue_screen_puts("\x1b[1D");
+					}
+				}
+				break;
 			case 27: // escape sequence
 				c = readChar();
 				if (c != '[') {