fcause ix: renderer: reset the cursor on the first line

We need to reset the cursor position on the first line before rendering.
Otherwise, it might mess up the first line being rendered.

Fixes: #1000
Fixes: 4624106 (feat: reduce console/term dependencies (#897))

screen_test.go

@@ -14,47 +14,47 @@ func TestClearMsg(t *testing.T) {
 		{
 			name:     "clear_screen",
 			cmds:     []Cmd{ClearScreen},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[2J\x1b[1;1H\x1b[1;1Hsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[2J\x1b[1;1H\x1b[1;1H\rsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
 		},
 		{
 			name:     "altscreen",
 			cmds:     []Cmd{EnterAltScreen, ExitAltScreen},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[?1049h\x1b[2J\x1b[1;1H\x1b[1;1H\x1b[?25l\x1b[?1049l\x1b[?25lsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[?1049h\x1b[2J\x1b[1;1H\x1b[1;1H\x1b[?25l\x1b[?1049l\x1b[?25l\rsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
 		},
 		{
 			name:     "altscreen_autoexit",
 			cmds:     []Cmd{EnterAltScreen},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[?1049h\x1b[2J\x1b[1;1H\x1b[1;1H\x1b[?25lsuccess\r\n\x1b[2;0H\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l\x1b[?1049l\x1b[?25h",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[?1049h\x1b[2J\x1b[1;1H\x1b[1;1H\x1b[?25l\rsuccess\r\n\x1b[2;0H\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l\x1b[?1049l\x1b[?25h",
 		},
 		{
 			name:     "mouse_cellmotion",
 			cmds:     []Cmd{EnableMouseCellMotion},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[?1002h\x1b[?1006hsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[?1002h\x1b[?1006h\rsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
 		},
 		{
 			name:     "mouse_allmotion",
 			cmds:     []Cmd{EnableMouseAllMotion},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[?1003h\x1b[?1006hsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[?1003h\x1b[?1006h\rsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
 		},
 		{
 			name:     "mouse_disable",
 			cmds:     []Cmd{EnableMouseAllMotion, DisableMouse},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[?1003h\x1b[?1006h\x1b[?1002l\x1b[?1003l\x1b[?1006lsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[?1003h\x1b[?1006h\x1b[?1002l\x1b[?1003l\x1b[?1006l\rsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
 		},
 		{
 			name:     "cursor_hide",
 			cmds:     []Cmd{HideCursor},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[?25lsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[?25l\rsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
 		},
 		{
 			name:     "cursor_hideshow",
 			cmds:     []Cmd{HideCursor, ShowCursor},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[?25l\x1b[?25hsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[?25l\x1b[?25h\rsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
 		},
 		{
 			name:     "bp_stop_start",
 			cmds:     []Cmd{DisableBracketedPaste, EnableBracketedPaste},
-			expected: "\x1b[?25l\x1b[?2004h\x1b[?2004l\x1b[?2004hsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
+			expected: "\x1b[?25l\x1b[?2004h\x1b[?2004l\x1b[?2004h\rsuccess\r\n\x1b[0D\x1b[2K\x1b[?2004l\x1b[?25h\x1b[?1002l\x1b[?1003l\x1b[?1006l",
 		},
 	}
 

standard_renderer.go

@@ -232,6 +232,12 @@ func (r *standardRenderer) flush() {
 				out.CursorDown(1)
 			}
 		} else {
+			if i == 0 && r.lastRender == "" {
+				// On first render, reset the cursor to the start of the line
+				// before writing anything.
+				buf.WriteByte('\r')
+			}
+
 			line := newLines[i]
 
 			// Truncate lines wider than the width of the window to avoid