diff mbox series

[v2,2/2] vnc: prioritize ZRLE compression over ZLIB

Message ID b5d129895d08a90d0a2a6183b95875bacfa998b8.1579582674.git.dirty@apple.com
State New
Headers show
Series vnc: fix VNC artifacts | expand

Commit Message

Cameron Esfahani via Jan. 21, 2020, 5 a.m. UTC 
In my investigation, ZRLE always compresses better than ZLIB so
prioritize ZRLE over ZLIB, even if the client hints that ZLIB is
preferred.

zlib buffer is always reset in zrle_compress_data(), so using offset to
calculate next_out and avail_out is useless.

Signed-off-by: Cameron Esfahani <dirty@apple.com>
---
 ui/vnc-enc-zrle.c |  4 ++--
 ui/vnc.c          | 11 +++++++++--
 2 files changed, 11 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/ui/vnc-enc-zrle.c b/ui/vnc-enc-zrle.c
index 17fd28a2e2..b4f71e32cf 100644
--- a/ui/vnc-enc-zrle.c
+++ b/ui/vnc-enc-zrle.c
@@ -98,8 +98,8 @@  static int zrle_compress_data(VncState *vs, int level)
     /* set pointers */
     zstream->next_in = vs->zrle->zrle.buffer;
     zstream->avail_in = vs->zrle->zrle.offset;
-    zstream->next_out = vs->zrle->zlib.buffer + vs->zrle->zlib.offset;
-    zstream->avail_out = vs->zrle->zlib.capacity - vs->zrle->zlib.offset;
+    zstream->next_out = vs->zrle->zlib.buffer;
+    zstream->avail_out = vs->zrle->zlib.capacity;
     zstream->data_type = Z_BINARY;
 
     /* start encoding */
diff --git a/ui/vnc.c b/ui/vnc.c
index 3e8d1f1207..1d7138a3a0 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -2071,8 +2071,15 @@  static void set_encodings(VncState *vs, int32_t *encodings, size_t n_encodings)
             break;
 #endif
         case VNC_ENCODING_ZLIB:
-            vs->features |= VNC_FEATURE_ZLIB_MASK;
-            vs->vnc_encoding = enc;
+            /*
+             * VNC_ENCODING_ZRLE compresses better than VNC_ENCODING_ZLIB.
+             * So prioritize ZRLE, even if the client hints that it prefers
+             * ZLIB.
+             */
+            if ((vs->features & VNC_FEATURE_ZRLE_MASK) == 0) {
+                vs->features |= VNC_FEATURE_ZLIB_MASK;
+                vs->vnc_encoding = enc;
+            }
             break;
         case VNC_ENCODING_ZRLE:
             vs->features |= VNC_FEATURE_ZRLE_MASK;