[vte] ring: Don't create streams for the alternate screen

[Egmont Koblinger <egmontkob src gnome org>]

commit 51cc5a7507ea28123c915ee8c5cfd7a10948bbf0
Author: Egmont Koblinger <egmont gmail com>
Date:   Sun Dec 14 23:21:17 2014 +0100

    ring: Don't create streams for the alternate screen
    
    https://bugzilla.gnome.org/show_bug.cgi?id=741480

 src/ring.c |   29 +++++++++++++++++++++--------
 src/ring.h |    3 ++-
 src/vte.c  |    4 ++--
 3 files changed, 25 insertions(+), 11 deletions(-)
---
diff --git a/src/ring.c b/src/ring.c
index 59330b2..2451871 100644
--- a/src/ring.c
+++ b/src/ring.c
@@ -51,7 +51,7 @@ _vte_ring_validate (VteRing * ring)
 
 
 void
-_vte_ring_init (VteRing *ring, gulong max_rows)
+_vte_ring_init (VteRing *ring, gulong max_rows, gboolean has_streams)
 {
        _vte_debug_print(VTE_DEBUG_RING, "New ring %p.\n", ring);
 
@@ -62,9 +62,14 @@ _vte_ring_init (VteRing *ring, gulong max_rows)
        ring->mask = 31;
        ring->array = g_malloc0 (sizeof (ring->array[0]) * (ring->mask + 1));
 
-       ring->attr_stream = _vte_file_stream_new ();
-       ring->text_stream = _vte_file_stream_new ();
-       ring->row_stream = _vte_file_stream_new ();
+       ring->has_streams = has_streams;
+       if (has_streams) {
+               ring->attr_stream = _vte_file_stream_new ();
+               ring->text_stream = _vte_file_stream_new ();
+               ring->row_stream = _vte_file_stream_new ();
+       } else {
+               ring->attr_stream = ring->text_stream = ring->row_stream = NULL;
+       }
 
        ring->last_attr_text_start_offset = 0;
        ring->last_attr.i = basic_cell.i.attr;
@@ -133,6 +138,8 @@ _vte_ring_freeze_row (VteRing *ring, gulong position, const VteRowData *row)
 
        _vte_debug_print (VTE_DEBUG_RING, "Freezing row %lu.\n", position);
 
+        g_assert(ring->has_streams);
+
        memset(&record, 0, sizeof (record));
        record.text_start_offset = _vte_stream_head (ring->text_stream);
        record.attr_start_offset = _vte_stream_head (ring->attr_stream);
@@ -206,6 +213,8 @@ _vte_ring_thaw_row (VteRing *ring, gulong position, VteRowData *row, gboolean do
 
        _vte_debug_print (VTE_DEBUG_RING, "Thawing row %lu.\n", position);
 
+        g_assert(ring->has_streams);
+
        _vte_row_data_clear (row);
 
        attr_change.text_end_offset = 0;
@@ -308,9 +317,11 @@ _vte_ring_reset_streams (VteRing *ring, gulong position)
 {
        _vte_debug_print (VTE_DEBUG_RING, "Reseting streams to %lu.\n", position);
 
-       _vte_stream_reset (ring->row_stream, position * sizeof (VteRowRecord));
-       _vte_stream_reset (ring->text_stream, 0);
-       _vte_stream_reset (ring->attr_stream, 0);
+       if (ring->has_streams) {
+               _vte_stream_reset (ring->row_stream, position * sizeof (VteRowRecord));
+               _vte_stream_reset (ring->text_stream, 0);
+               _vte_stream_reset (ring->attr_stream, 0);
+       }
 
        ring->last_attr_text_start_offset = 0;
        ring->last_attr.i = basic_cell.i.attr;
@@ -608,7 +619,9 @@ _vte_ring_append (VteRing * ring)
  * _vte_ring_set_visible_rows_hint:
  * @ring: a #VteRing
  *
- * Set the number of visible rows, a hint only for better performance.
+ * Set the number of visible rows, a hint for better performance.
+ * It's no longer a hint only; it's required to be set correctly
+ * for the alternate screen so that it never hits the streams.
  */
 void
 _vte_ring_set_visible_rows_hint (VteRing *ring, gulong rows)
diff --git a/src/ring.h b/src/ring.h
index c23b06d..1490ed5 100644
--- a/src/ring.h
+++ b/src/ring.h
@@ -65,6 +65,7 @@ struct _VteRing {
        VteRowData cached_row;
        gulong cached_row_num;
 
+       gboolean has_streams;
        gulong visible_rows_hint;  /* to keep at least a screenful of lines in memory, bug 646098 comment 12 
*/
 };
 
@@ -78,7 +79,7 @@ struct _VteRing {
 const VteRowData *_vte_ring_index (VteRing *ring, gulong position);
 VteRowData *_vte_ring_index_writable (VteRing *ring, gulong position);
 
-void _vte_ring_init (VteRing *ring, gulong max_rows);
+void _vte_ring_init (VteRing *ring, gulong max_rows, gboolean has_streams);
 void _vte_ring_fini (VteRing *ring);
 void _vte_ring_reset (VteRing *ring);
 void _vte_ring_resize (VteRing *ring, gulong max_rows);
diff --git a/src/vte.c b/src/vte.c
index 07508c4..bcd4b21 100644
--- a/src/vte.c
+++ b/src/vte.c
@@ -8023,9 +8023,9 @@ vte_terminal_init(VteTerminal *terminal)
        /* We allocated zeroed memory, just fill in non-zero stuff. */
 
        /* Initialize the screens and histories. */
-       _vte_ring_init (pvt->alternate_screen.row_data, terminal->pvt->row_count);
+       _vte_ring_init (pvt->alternate_screen.row_data, terminal->pvt->row_count, FALSE);
        pvt->screen = &terminal->pvt->alternate_screen;
-       _vte_ring_init (pvt->normal_screen.row_data,  VTE_SCROLLBACK_INIT);
+       _vte_ring_init (pvt->normal_screen.row_data,  VTE_SCROLLBACK_INIT, TRUE);
        pvt->screen = &terminal->pvt->normal_screen;
 
        _vte_terminal_set_default_attributes(terminal);