[mutter/wip/carlosg/incr-is-fubar: 15/18] x11: Don't exceed transfer size in INCR chunks

[Carlos Garnacho <carlosg src gnome org>]

commit c56fb43d01715885d276dd55bc290283ef9f2f13
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Apr 11 17:21:20 2020 +0200

    x11: Don't exceed transfer size in INCR chunks
    
    The stream automatically flushes after data size exceeds the
    size we deem for INCR chunks, but we still try to copy it all.
    Actually limit the data we copy, and leave the rest for future
    INCR chunks.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1198

 src/x11/meta-x11-selection-output-stream.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/src/x11/meta-x11-selection-output-stream.c b/src/x11/meta-x11-selection-output-stream.c
index 4cdde8ab3..7179074e9 100644
--- a/src/x11/meta-x11-selection-output-stream.c
+++ b/src/x11/meta-x11-selection-output-stream.c
@@ -203,7 +203,7 @@ meta_x11_selection_output_stream_perform_flush (MetaX11SelectionOutputStream *st
   MetaX11SelectionOutputStreamPrivate *priv =
     meta_x11_selection_output_stream_get_instance_private (stream);
   Display *xdisplay;
-  size_t element_size, n_elements;
+  size_t element_size, n_elements, max_size;
   gboolean first_chunk = FALSE;
   int error_code;
 
@@ -218,6 +218,7 @@ meta_x11_selection_output_stream_perform_flush (MetaX11SelectionOutputStream *st
 
   element_size = get_element_size (priv->format);
   n_elements = priv->data->len / element_size;
+  max_size = get_max_request_size (priv->x11_display);
 
   if (!priv->incr)
     first_chunk = TRUE;
@@ -247,9 +248,13 @@ meta_x11_selection_output_stream_perform_flush (MetaX11SelectionOutputStream *st
     }
   else
     {
+      size_t copy_n_elements;
+
       if (priv->incr && priv->data->len > 0)
         priv->delete_pending = TRUE;
 
+      copy_n_elements = MIN (n_elements, max_size / element_size);
+
       XChangeProperty (xdisplay,
                        priv->xwindow,
                        priv->xproperty,
@@ -257,8 +262,8 @@ meta_x11_selection_output_stream_perform_flush (MetaX11SelectionOutputStream *st
                        priv->format,
                        PropModeReplace,
                        priv->data->data,
-                       n_elements);
-      g_byte_array_remove_range (priv->data, 0, n_elements * element_size);
+                       copy_n_elements);
+      g_byte_array_remove_range (priv->data, 0, copy_n_elements * element_size);
     }
 
   if (first_chunk)