From 81172effba7c70d3b2932c67be79a2924eae9d73 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jonas=20=C3=85dahl?= <jadahl@gmail.com>
Date: Mon, 12 Oct 2020 17:34:30 +0200
Subject: [PATCH] vnc: Copy pixels using the right destination stride

We're copying the pixels in a separate thread managed by PipeWire, and
in this thread, accessing the VNC framebuffer dimension and stride is
racy. Instead of fetching the dimension directly, pass the expected
width and get the stride it will eventually have.

Already before this patch, when the copied pixel end up on the main
thread and the dimension still doesn't match up, the frame will be
dropped.
---
 src/grd-session-vnc.c         | 5 +++--
 src/grd-session-vnc.h         | 3 ++-
 src/grd-vnc-pipewire-stream.c | 5 +++--
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/grd-session-vnc.c b/src/grd-session-vnc.c
index 69fb33d..f4835aa 100644
--- a/src/grd-session-vnc.c
+++ b/src/grd-session-vnc.c
@@ -535,9 +535,10 @@ grd_session_vnc_get_fd (GrdSessionVnc *session_vnc)
 }
 
 int
-grd_session_vnc_get_framebuffer_stride (GrdSessionVnc *session_vnc)
+grd_session_vnc_get_stride_for_width (GrdSessionVnc *session_vnc,
+                                      int            width)
 {
-  return session_vnc->rfb_screen->paddedWidthInBytes;
+  return width * BGRX_BYTES_PER_PIXEL;
 }
 
 rfbClientPtr
diff --git a/src/grd-session-vnc.h b/src/grd-session-vnc.h
index 0d01ad3..ccd046c 100644
--- a/src/grd-session-vnc.h
+++ b/src/grd-session-vnc.h
@@ -60,7 +60,8 @@ void grd_session_vnc_move_cursor (GrdSessionVnc *session_vnc,
 
 int grd_session_vnc_get_fd (GrdSessionVnc *session_vnc);
 
-int grd_session_vnc_get_framebuffer_stride (GrdSessionVnc *session_vnc);
+int grd_session_vnc_get_stride_for_width (GrdSessionVnc *session_vnc,
+                                          int            width);
 
 gboolean grd_session_vnc_is_client_gone (GrdSessionVnc *session_vnc);
 
diff --git a/src/grd-vnc-pipewire-stream.c b/src/grd-vnc-pipewire-stream.c
index 96dd7c9..82ceb9b 100644
--- a/src/grd-vnc-pipewire-stream.c
+++ b/src/grd-vnc-pipewire-stream.c
@@ -326,10 +326,11 @@ process_buffer (GrdVncPipeWireStream *stream,
       int height;
       int y;
 
-      src_stride = buffer->datas[0].chunk->stride;
-      dst_stride = grd_session_vnc_get_framebuffer_stride (stream->session);
       height = stream->spa_format.size.height;
       width = stream->spa_format.size.width;
+      src_stride = buffer->datas[0].chunk->stride;
+      dst_stride = grd_session_vnc_get_stride_for_width (stream->session,
+                                                         width);
 
       frame->data = g_malloc (height * dst_stride);
       for (y = 0; y < height; y++)
-- 
2.28.0