[mutter/wip/carlosg/incr-is-fubar: 26/27] x11: Don't exceed transfer size in INCR chunks

[Carlos Garnacho <carlosg src gnome org>]

commit 3c72ab5fe9ce0f9f0850ad82eee9049bcac13bbd
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 42abd99c1..877995ac1 100644
--- a/src/x11/meta-x11-selection-output-stream.c
+++ b/src/x11/meta-x11-selection-output-stream.c
@@ -199,7 +199,7 @@ 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;
 
@@ -214,6 +214,7 @@ 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;
@@ -243,6 +244,8 @@ meta_x11_selection_output_stream_perform_flush (MetaX11SelectionOutputStream *st
     }
   else
     {
+      size_t copy_n_elements;
+
       if (priv->data->len == 0)
         {
           priv->closing = FALSE;
@@ -255,6 +258,8 @@ meta_x11_selection_output_stream_perform_flush (MetaX11SelectionOutputStream *st
             priv->closing = TRUE;
         }
 
+      copy_n_elements = MIN (n_elements, max_size / element_size);
+
       XChangeProperty (xdisplay,
                        priv->xwindow,
                        priv->xproperty,
@@ -262,8 +267,8 @@ 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)