[mutter/wip/carlosg/incr-is-fubar: 2/11] x11: Flag flushes despite having less than the element size

[Carlos Garnacho <carlosg src gnome org>]

commit 7479d58307ddc412b3892978db93d04c8e60cd09
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Apr 10 17:24:14 2020 +0200

    x11: Flag flushes despite having less than the element size
    
    If say we want 32bit data, but have 2 bytes stored, we would simply
    ignore flush requests. Allow (and don't clear) the needs_flush flag
    if we have less than the element size accumulated.
    
    Instead handle this in can_flush(), so it's triggered whenever we
    have enough data to fill 1 element, or if the stream is closing
    (seems a broken situation, but triggered by the caller).
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1198

 src/x11/meta-x11-selection-output-stream.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/src/x11/meta-x11-selection-output-stream.c b/src/x11/meta-x11-selection-output-stream.c
index a3ac76629..67b375b28 100644
--- a/src/x11/meta-x11-selection-output-stream.c
+++ b/src/x11/meta-x11-selection-output-stream.c
@@ -60,6 +60,8 @@ G_DEFINE_TYPE_WITH_PRIVATE (MetaX11SelectionOutputStream,
                             meta_x11_selection_output_stream,
                             G_TYPE_OUTPUT_STREAM);
 
+static size_t get_element_size (int format);
+
 static void
 meta_x11_selection_output_stream_notify_selection (MetaX11SelectionOutputStream *stream)
 {
@@ -97,6 +99,9 @@ meta_x11_selection_output_stream_can_flush (MetaX11SelectionOutputStream *stream
 
   if (priv->delete_pending)
     return FALSE;
+  if (!g_output_stream_is_closing (G_OUTPUT_STREAM (stream)) &&
+      priv->data->len < get_element_size (priv->format))
+    return FALSE;
 
   return TRUE;
 }
@@ -241,7 +246,7 @@ meta_x11_selection_output_stream_perform_flush (MetaX11SelectionOutputStream *st
                        priv->data->data,
                        n_elements);
       g_byte_array_remove_range (priv->data, 0, n_elements * element_size);
-      if (priv->data->len < element_size)
+      if (priv->data->len == 0)
         priv->flush_requested = FALSE;
     }
 
@@ -391,7 +396,7 @@ meta_x11_selection_output_request_flush (MetaX11SelectionOutputStream *stream)
 
   g_mutex_lock (&priv->mutex);
 
-  if (priv->data->len >= get_element_size (priv->format))
+  if (priv->data->len > 0)
     priv->flush_requested = TRUE;
 
   needs_flush = meta_x11_selection_output_stream_needs_flush_unlocked (stream);