Switch screen functionality

There's 2 "screens" that I've called main and alternate here
Switching the screen allows doing things without impact the main one

vim and less use this which is why when you quit you have no evidance of it

Author: mikeymike

src/UnixTerminal.php

@@ -229,6 +229,16 @@ public function moveCursorToColumn(int $column) : void
         $this->output->write(sprintf("\033[%dC", $column));
     }
 
+    public function showAlternateScreen() : void
+    {
+        $this->output->write("\033[?47h");
+    }
+
+    public function showMainScreen() : void
+    {
+        $this->output->write("\033[?47l");
+    }
+
     /**
      * Read bytes from the input stream
      */

test/UnixTerminalTest.php

@@ -229,6 +229,28 @@ public function testMoveCursorToColumn() : void
         self::assertEquals("\033[10C", $output->fetch());
     }
 
+    public function testShowAlternateScreen() : void
+    {
+        $input  = $this->createMock(InputStream::class);
+        $output = new BufferedOutput;
+
+        $terminal = new UnixTerminal($input, $output);
+        $terminal->showAlternateScreen();
+
+        self::assertEquals("\033[?47h", $output->fetch());
+    }
+
+    public function testShowMainScreen() : void
+    {
+        $input  = $this->createMock(InputStream::class);
+        $output = new BufferedOutput;
+
+        $terminal = new UnixTerminal($input, $output);
+        $terminal->showMainScreen();
+
+        self::assertEquals("\033[?47l", $output->fetch());
+    }
+
     public function testRead() : void
     {
         $tempStream = fopen('php://temp', 'r+');