ui/vnc: fix tight palette pixel encoding for 8/16-bpp formats

When sending a tight rectangle with the palette filter, if the client
format was 8/16bpp, the colours on big endian hosts are not set as
we're sending the wrong bytes. We must first cast the 32-bit colour
to a 16/8-bit value, and then send the result.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
(cherry picked from commit 63d3209)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

Author: berrange

ui/vnc-enc-tight.c

@@ -1001,16 +1001,24 @@ static int send_mono_rect(VncState *vs, int x, int y,
         break;
     }
     case 2:
-        vnc_write(vs, &bg, 2);
-        vnc_write(vs, &fg, 2);
+    {
+        uint16_t bg16 = bg;
+        uint16_t fg16 = fg;
+        vnc_write(vs, &bg16, 2);
+        vnc_write(vs, &fg16, 2);
         tight_encode_mono_rect16(vs->tight->tight.buffer, w, h, bg, fg);
         break;
+    }
     default:
-        vnc_write_u8(vs, bg);
-        vnc_write_u8(vs, fg);
+    {
+        uint8_t bg8 = bg;
+        uint8_t fg8 = fg;
+        vnc_write_u8(vs, bg8);
+        vnc_write_u8(vs, fg8);
         tight_encode_mono_rect8(vs->tight->tight.buffer, w, h, bg, fg);
         break;
     }
+    }
     vs->tight->tight.offset = bytes;
 
     bytes = tight_compress_data(vs, stream, bytes, level, Z_DEFAULT_STRATEGY);